# Patent

## Title
Preparation of α-hydroxy and α-amino ketones

## Abstract

A process for the preparation of an 1,1-disubstituted oxirane is disclosed, wherein an organic sulphide is reacted in a polar solvent with an educt containing a leaving group attached to a primary or secondary carbon atom, and/or the sulfonium salt formed in this way is reacted with a ketone in presence of a base and a polar solvent. Oxiranes of the type obtained may be further converted into the corresponding α-hydroxyketone or α-aminoketone, either in one step by subjecting to aerobic oxidation in the presence of a transition metal catalyst, or in two steps by hydrolyzation in the presence of an aqueous acid to the corresponding dialcohol and subsequent selective oxidation. Further described are some novel epoxide intermediates. The α-hydroxyketones and α-aminoketones thus obtainable are useful inter alga as photoinitiators.

## Background
The present invention relates to a process for the preparation of an 1,1-disubstituted oxirane, its oxidative opening in one or two reaction steps with formation of an α-hydroxyketone or α-aminoketone, and to some novel epoxide intermediates.
Compounds of the α-hydroxyketone class may be employed in many technical fields, one of them being the initiation of chemical reactions on irradiation.
Oxiranes or epoxides are 3-membered rings comprising 2 carbon atoms and 1 oxygen atom. Preparation of certain substituted oxiranes by reaction of a carbonyl compound with a sulphur-ylide is described in U.S. Pat. No. 3,455,967.
Known oxidation reactions of epoxides, some of them yielding α-hydroxyketones, are compiled for example in Synthesis 2003, No. 18, pp. 2753-2762. Conversion to α-hydroxyketones usually requires several steps, high amounts of reagents or catalysts.
SUMMARY OF THE INVENTION
It has now been found that an arylmethyl sulphonium salt capable of building a sulphur-ylide may conveniently and in good yield be converted into an epoxide by reaction with a ketone and a base in presence of a polar solvent.
The sulphonium salt may conveniently be prepared in situ by reacting a suitable organic sulphide in a polar solvent with an educt wherein a leaving group is attached to a primary or secondary carbon atom.
The epoxide may conveniently be converted into the desired hydroxyketone or aminoketone by methods known in the art. A further finding of the invention is that, surprisingly, a single reaction step may lead to the desired end product in an even more convenient manner by catalytic opening with aerobic partial oxidation.
The following scheme summarizes an example of the present invention:




where inter alia each of R and R′′ may denote hydrogen or hydrocarbyl such as alkyl, and R′ is hydrocarbyl such as alkyl.

Preparation of the Epoxide

Thus, the present invention includes a process for the preparation of an 1,1-dicarbo substituted epoxide, which process comprises

    i) reacting a suitable organic sulphide in a polar solvent with an educt wherein a leaving group is attached to a benzylic moiety, and reacting the product
    ii) with a ketone in presence of a base and a polar solvent.


Suitable organic sulphides, also recalled as thio ethers, include dialkyl sulphides, alkyl-aryl sulphides and alkyl-cycloalkyl sulphides. Preferred sulphides conform to the formula: R—S—R′, wherein R is alkyl, e.g. of 1 to 20 carbon atoms, which is unsubstituted or substituted by C5-C12cycloalkyl or phenyl, and R′ is as defined for R′ or is C5-C12cycloalkyl, phenyl, phenyl substituted by C1-C12alkyl; or R and R′ together are penta- or hexamethylene, which may be substituted by C1-C12alkyl or phenyl. Most preferred sulphides are (C1-C4alkyl)2S such as dimethyl sulphide, tetrahydrothiophene, or a sulphide A1CH2—S—CH2A1, where A1 is the same as used in the educt explained below.
Advantageously, the sulphide is recovered after step (ii) and used again for another batch of step (i) or is, in case of a continuous reaction, reentered into the system before step (i).
In step (i), the educt wherein a leaving group is attached to a benzylic moiety usually is of the formula X

A1-CH2—X  (X)

wherein X is the leaving group, preferably selected from halogen, OH, OAc, wherein halogen usually is I, Br or Cl and Ac stands for an acyl residue of a suitable carboxylic or preferably sulphonic acid such as toluene sulphonic acid (tosyl), bromophenylsulphonic acid (brosyl), nitrophenylsulphonic acid (nosyl), trifluoromethylsulphonic acid, and A1 is as defined below.

Reaction step (i) is preferably carried out with heating, e.g. at a temperature ranging from 25° C. to reflux temperature, e.g. between 30 and 150° C., preferably between 50 and 120° C.
Organic sulphide and leaving group in the benzylic educt are often employed in about equimolar amounts, e.g. 0.7 to 1.5, preferably 0.9 to 1.1 equivalents of organic sulphide on one equivalent of leaving group.
In reaction step (i), frequently a non-polar solvent is used concomitantly, e.g. an aliphatic or aromatic hydrocarbon or mixture of such solvents such as toluene, xylene, petrol ether etc. This usually results in the formation of a 2 phase system in the beginning of the reaction, which may turn into a 1 phase system with increasing amount of sulphonium salt formed. A phase transfer catalyst may be added but usually is not required. Mixing during the reaction is usually effected by stirring and/or refluxing.
The sulphonium salt formed in step (i) may conform to the formula:




wherein R is alkyl, e.g. of 1 to 20 carbon atoms, which is unsubstituted or substituted by C5-C12cycloalkyl or phenyl, and R′ is as defined for R or is C5-C12cycloalkyl, phenyl, phenyl substituted by C1-C12alkyl; or R and R′ together are penta- or hexamethylene, which may be substituted by C1-C12alkyl or phenyl; A1 is as defined below; and

    X′− is a suitable anion, e.g. the anion of the leaving group of the compound of formula X such as halogenide, hydroxyl, acylate etc., or another suitable anion such as sulfate, hydrogensulfate, BF4−, PF6− (introduced, for example, by ion exchange). Advantageously, the sulphonium salt formed in step (i) is not isolated, and the reaction mixture is used for step (ii) without further purification or other treatment.


Naturally, it is also possible to start the present process using the sulphonium salt from any source, and reacting it with a ketone and a base in presence of a polar solvent. In this case, reaction conditions are as described for step (ii) of the process of the invention.
Surprisingly, the reaction of ketone and sulphonium salt obtained in step (i) under the present condition clearly dominates over 2 important competing side reactions, i.e.

    1. the aldol condensation of the ketone and
    2. base-induced rearrangement of the sulphonium salt with alkylation of the aromatic ring. Thus, pre-mixing of ketone and base as well as pre-mixing of sulphonium salt and base becomes possible, and the reaction proceeds immediately after completion of the reaction mixture, yielding the desired epoxide in good yield. Of course, other sequences are possible, such as mixing of the product from step (i) with ketone followed by addition of the base.


Preferred polar solvents in both steps (i) and (ii) are selected from water, alcohols such as methyl, ethyl or propyl alcohol, or mixtures of these solvents.
Typically, polar solvents in step (i) include water, alcohols such as methyl, ethyl or propyl alcohol, ketones or sulphides, such as the sulphide used as educt in step (i), or mixtures of these solvents such as alcohol-water mixtures. Most preferred polar solvent is water. Typical polar solvents in step (ii) include water, alcohols such as methyl, ethyl or propyl alcohol, ketones, such as the ketone used in the reaction step (ii), sulphides, mixtures of these solvents such as alcohol-water mixtures, or mixtures of one or more of these polar solvents with a cosolvent selected from aromatic solvents such as benzene, toluene, xylene, and ethers. More preferred are water, alcohols or mixtures thereof, or mixtures of one or more of these polar solvents with a cosolvent as given above, where the volume ratio cosolvent:polar solvent is smaller than 2:1, especially smaller than 1:1.
Most preferred polar solvent in step (ii) is an alcohol such as a C1-C4alkohol, especially methanol, ethanol.
Reaction step (ii) is preferably carried out at a temperature ranging from about −10° C. to about 50° C., e.g. between 0 and 40° C., preferably at about room temperature or below 25° C.
Preferred base is a metal hydroxyde, mainly an alkaline hydroxide such as LiOH, NaOH, KOH or mixtures thereof. Most preferred is NaOH. The base is preferably used as a concentrated solution (e.g. 20-50% base by total weight of the solution) in water, alcohol or water/alcohol mixture. The base is usually employed in about equimolar amount or in slight excess, relative to the ketone, for example 0.9 mol-1.5 mol hydroxide on 1 mol ketone.
In a preferred process, the ketone is of the formula A2-CO-A3, where A2 and A3 are as defined below. Examples for preferred ketones include acetone, ethyl methyl ketone, cyclohexanone. The ketone is usually employed in about equimolar amount or in excess, relative to the sulphonium salt present from step (i). The ketone may also be used as a solvent or cosolvent in step (ii), amounts ranging, for example, from 0.9 mol to about 20 mol, preferably from 1 to 10 mol ketone per mol sulphonium salt.
The epoxide obtainable in the present process is a 1,1-dicarbo substituted ethylene oxide (oxirane), for example of the formula




or of the formula II described further below.

A benzylic educt is used in step (i), which means that the leaving group in said educt is attached to an arylmethyl moiety such as benzyl, which may be unsubstituted or substituted in the phenyl moiety. Consequently, in the educts and products usually employed, A1 is an aromatic organic carbon anchor group, and A2 and A3 each are an organic group containing at least one carbon atom linked to the carbon carrying the oxygen bond. Each of A1 may contain one or more further structures reactive in the above steps (i) or (ii), i.e. methylene-X or methylene-sulphonium, which are converted in the reaction. In a preferred process, A1 in formula X or in the sulphonium salt, and consequently in the product obtained, is an aryl group, which may carry one or more further structures modified in the present reaction, while no such structures are present in A2 and A3.
Each of A2, A3 may also contain one or more further keto structures which are converted in the reaction.
In a more preferred process, the 1,1-dicarbo substituted oxirane is a compound of the formula II




wherein

    A1, if n is 1, include carbocyclic aryl which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, Aro, and/or by alkyl, alkoxy, alkenyl or alkenyloxy, each of which itself is unsubstituted or substituted by OPr, halogen, NR9R10, carboxy, Aro, COR1, SO2R2, nitro, CN; or is carbocyclic aryl substituted by O—R8—O—SiR11R12R13; if n is 2, preferred meanings of A1 include Ar—R5—Ar; or is a residue R11R12Si(O—R8—O—Ar)2; if n is 3, preferred meanings of A1 include a residue (Ar)3—R6; or is a residue R11Si(O—R8—O—Ar)3;
    if n is 4, preferred meanings of A1 include a residue (Ar)4—R7.
    A2 and A3 preferably are alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, alkylaryl, arylalkyl, cycloalkylalkyl, or one of said residues substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN; and/or, if containing at least 3 carbon atoms, are interrupted in a carbon-carbon single bond by O, NR9, COO, OCONR9, CONR9;
    or A2 and A3 together are C4-C11alkylene, -oxaalkylene, -azaalkylene or -alkenylene, each of which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, and/or by alkyl, alkoxy, alkenyl, alkenyloxy, each of which itself is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN.


In the above definitions, Ar stands for a divalent carbocyclic aryl which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, Aro, alkyl, alkoxy; Aro stands for aryloxy which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, alkyl, alkoxy, alkenyl, alkenyloxy;

    Pr stands for hydrogen or a protecting group;
    R1 is hydrogen, OH, alkyl, alkenyl, cycloalkyl, cycloalkenyl, phenyl, alkylphenyl, alkoxyphenyl, alkoxy, alkenoxy, cycloalkoxy, cycloalkenoxy, phenoxy, alkylphenoxy, alkoxyphenoxy;
    R2 is OH, alkyl or alkoxy;
    R3 is alkyl, alkenyl, cycloalkyl, cycloalkenyl, phenyl, alkylphenyl, alkoxyphenyl;
    R4 and R′4 independently are hydrogen, C1-C12alkyl or cyclohexyl;
    R5, R6 and R7 independently are spacer groups of suitable valency to covalently bond the Ar moieties they are attached to; or R5 is a direct bond;
    R8 is a divalent aliphatic or cycloaliphatic residue;
    R9 and R10 independently are hydrogen, C1-C12alkyl, C1-C12alkyl substituted by OPr and/or NR4R′4, C5-C12cycloalkyl; or R9 and R10 are joined together to form a tetramethylene, pentamethylene, oxatetramethylene or oxapentamethylene moiety;
    R11 and R12 independently are C1-C12alkyl or C1-C12alkoxy.


Preferably, the product obtained in this process is subsequently converted into an α-hydroxy- or aminoketone, e.g. by methods known in the art or in analogy to such methods, e.g. by suitable hydrolysis or aminolysis methods; especially preferred is the conversion by one of the methods described below.
The epoxide product obtained may be used for the subsequent reactions described below without further purification.
Oxidative Epoxide Opening in 1 Step
It has been found that epoxides, such as those defined above, may conveniently be converted into α-hydroxyketones in a single step (v) using a transition metal catalyst under aerobic conditions.
Thus, present invention also pertains to a process for the preparation of an alpha-hydroxy ketone, characterized in that a 1,1-dicarbo substituted 2-hydro-ethylene oxide is objected to aerobic oxidation in the presence of a transition metal catalyst.
The 1,1-dicarbo substituted ethylene oxide (oxirane) educt is, for example, a compound of the formula




wherein A1 is hydrogen or an organic carbon anchor group, and A2 and A3 denote the 1,1-dicarbo substituents, each of which, and the organic carbon anchor group A1, if present, are selected from any organic group able to form a carbon-carbon single bond to the carbon atom No. 1 of the oxirane ring, or carbon atom No. 2 in case of A1. Each of A1, A2, A3 may contain one or more further structures of the type 1,1-dicarbo substituted 2-hydro-ethylene oxide which are converted in the reaction. In a preferred process, A1 in formula II′ or the below formula (I is a carbon anchor group, especially an aryl group, which may carry one or more further structures





or A1 itself is this structure, to be converted in the present process, while no such structures are present in A2 and A3.

The alpha-hydroxy ketone formed is preferably a compound of the formula I




wherein n ranges from 1 to 4.

The educt preferably is a compound of the formula II




wherein A1, A2 and A3 and n are as defined above.

Preferably, the reaction is carried out in the presence of water; the transition metal catalyst is mainly selected from those of the metals Pd, Ru, Cu, Fe, Mn, Co, Mo, W, V, Ti, Os, Ta, Pt, usually employed as a metal (oxidation state 0) or in low oxidation state (e.g. I or II), e.g. as a corresponding complex (see below); preferred is a suitable Pd catalyst (e.g. Pd(II)/Pd(0) system).
The transition metal catalyst employed in the present process usually is a complex containing one or more ligands bonded to the transition metal as central atom. In general, ligands may be those described in WO 98/39346 for compounds of formulae I-III explained therein. Preferred are chelating ligands, such as bidentate or tridentate ligands, especially those containing nitrogen. Use of this catalyst for the aerobic oxidation of a 1,1-dicarbo substituted ethylene oxide such as the above compound of formula II is another subject of present invention.
Appropriate monodentate, bidentate and tetradentate neutral e− donor ligands are derived, for example, from unsubstituted or substituted heteroarenes such as furan, thiophene, pyrrole, pyridine, bipyridine, picolylimine, γ-pyran, γ-thiopyran, phenanthroline, pyrimidine, bipyrimidine, pyrazine, indole, coumarone, thionaphthene, carbazole, dibenzofuran, dibenzothiophene, pyrazole, imidazole, benzimidazole, oxazole, thiazole, dithiazole, isoxazole, isothiazole, quinoline, bisquinoline, isoquinoline, bisisoquinoline, acridine, chromene, phenazine, phenoxazine, phenothiazine, triazine, thianthrene, purine, bisimidazole and bisoxazole. Examples of substituents are OH, halogen, C(O)ORs1, OC(O)Rs4, C(O)Rs2, nitro, NH2, cyano, SO3My, OSO3My, NR20SO3My, N═N—Rs2, C1-C12alkyl, C2-C12alkenyl, C1-C12alkoxy, C3-C12-cycloalkyl, C3-C12cycloal kenyl, C2-C11heterocycloalkyl, C2-C11heterocycloalkenyl, C6-C10-aryl, C6-C10aryloxy, C5-C9heteroaryl, C5-C9heteroaryloxy, C7-C11aralkyl, C7-C11aralkyloxy, C6-C10-heteroaralkyl, C8-C11aralkenyl, C7-C10heteroaralkenyl, monoamino, diamino, sulphonyl, sulphonamide, carbamide, carbamate, sulphohydrazide, carbohydrazide, carbohydroxamic acid residue and aminocarbonylamide, in which Rs1 is hydrogen, My, C1-C12alkyl, C2-C12alkenyl, C3-C12cycloalkyl, C2-C11heterocycloalkyl, C6-C10aryl, C5-C9heteroaryl, C7-C11aralkyl or C6-C10-heteroaralkyl, Rs4 is hydrogen, C1-C12alkyl, C2-C12alkenyl, C3-C12cycloalkyl, C2-C11-hetero-cycloalkyl, C6-C10aryl, C5-C9heteroaryl, C7-C11aralkyl or C6-C10heteroaralkyl, and Rs2 and R20 are hydrogen, C1-C12alkyl, C2-C12alkenyl, C3-C12cycloalkyl, C3-C12cycloalkenyl, C2-C11hetero-cycloalkyl, C2-C11heterocycloalkenyl, C6-C10aryl, C5-C9heteroaryl, C7-C11aralkyl, C6-C10hetero-aralkyl, C8-C11aralkenyl or C7-C10heteroaralkenyl, and alkyl, alkenyl, alkoxy, cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, aryl, aryloxy, heteroaryl, heteroaryloxy, aralkyl, aralkyloxy, heteroaralkyl, aralkenyl and heteroaralkenyl in turn are unsubstituted or substituted by one of the abovementioned substituents; and y is 1 and M is a monovalent metal or y is 1/2  and M is a divalent metal.
Most preferred ligands are phenanthroline or substituted phenanthroline such as 2,9-dimethylphenanthroline (cuproine), bathocuproine,




The reaction may be carried out with homogeneous catalysis or heterogeneous catalysis, e.g. by using the transition metal catalyst in immobilized form.
The catalyst may conveniently be prepared in situ from a suitable transition metal salt and a ligand; appropriate salts include halogenides, anions of inorganic oxygen acids or carboxylates, especially acetates.
Water is preferably present in amounts about equivalent to the amount of epoxide in the educt present or in excess, for example in an amount of 0.8 to 100000 mol water per equivalent epoxide, preferably about 1 to 10000, more preferably about 5 to 2000 mol water per equivalent epoxide.
The aerobic oxidation is preferably effected by the presence of gaseous oxygen and/or a molecular oxygen releasing agent. Gaseous oxygen may be applied in the form of pure oxygen or mixtures with other gases, mainly inert gases, such as nitrogen, argon etc.; air is suitable. The pressure is not critical, preferably the reaction is carried out in the range 0.1-300 bar, advantageously at or near atmospheric pressure (e.g. 0.5-3 bar).
As molecular oxygen releasing agent any chemical or mixture may be employed, which is able to release gaseous oxygen; examples are oxo- or peroxo compounds which are decomposed under the conditions of the reaction or after addition of a second component of the agent (e.g. hydrogen peroxide, organic hydroperoxides such as tert.butyl-hydroperoxide, inorganic oxides or peroxides such as manganese (per)oxide, (per)chlorates etc.).
Reaction temperature is advantageously chosen in correlation to the pressure applied, e.g. from the range −10 to 200° C., more preferably 0-150° C., especially 15-110° C.; usually the reaction is carried out with the educt in the liquid state, e.g. using a suitable solvent. The solvent may be water or an organic solvent, preferably miscible with water. Most preferably no further organic solvent is added, e.g. in that way that the reaction is carried out in the presence of water as the only solvent.
Oxidative Epoxide Opening in 2 Steps
Alternatively to the 1-step reaction described above, the conversion of the epoxide into the α-hydroxyketone may also be effected by acidic hydrolysis (iii) followed by selective oxidation (iv). Similarly, aminolysis (iii′) followed by selective oxidation (iv′) leads to an α-aminoketone. Thus, the present invention further pertains to the conversion of a 1,1-dicarbo substituted oxirane into an alpha-hydroxy ketone, characterized in that

    
    
        iii) the 1,1-dicarbo substituted oxirane is hydrolyzed in the presence of an aqueous acid to the corresponding dialcohol,
        iv) and the product obtained is treated with an oxidizing agent selected from hypochlorite, hypobromite, hypervalent iodine reagents.
    
    


Advantageously, the dialcohol formed in step (iii) is not isolated, and the reaction mixture is used for step (iv) without further purification or other treatment.
For analogous conversion into the α-aminoketone, step (iii) in the above sequence may be replaced by

    
    
        iii′) aminolysis of the 1,1-dicarbo substituted oxirane in the presence of a catalyst to the corresponding alpha-aminoalcohol.
    
    


Oxidation of the alcohol function to carbonyl in subsequent step (iv′), optionally after isolation of the desired 1,1-dicarbo-1-amino-2-hydroxy-2-arylethane intermediate, may be effected in analogy to step (iv) described below. Aminolysis in step iii′) as well as hydrolysis in step iii) or any isolation, workup or purification step included, may be carried out according to methods known in the art or in close analogy to such methods.
Preferably, the amine used in step iii′) is selected from ammonia, primary and secondary amines and corresponding amides such as alkaline amides. Thus, a preferred amine corresponds to the formula V

YN(R18)(R19)  (V)

wherein

    Y stands for H or an alkali metal, especially Li, Na, K, and


R18 and R19, independently, are selected from H, C1-C4alkyl, or are joined together to form a tetramethylene, pentamethylene, oxatetramethylene, oxapentamethylene, or an azatetramethylene or azapentamethylene moiety, wherein the nitrogen atom is unsubstituted (NH) or is substituted by C1-C4alkyl.
When Y is H, the catalyst may be an acid, e.g. as described for step iii) below. Preferably, a base functions as the catalyst, such as the compound of the formula V itself, or a mixture of such compounds.
In step (iii′), the reaction is preferably carried out in presence of a solvent or an excess of the amine (V) functioning as a solvent. Suitable inert solvents are, for example, aliphatic or aromatic hydrocarbons, e.g. hexane, heptane, octane, liquid hydrocarbon fractions like ligroin or petrol ether, benzene, toluene xylene and the like, amines (e.g. aromatic amines such as pyridine) or ethers. If desired, the reaction may be carried out under pressure, e.g. sufficient for the liquification of the amine used.
Temperature may range, for example, from about −20° C. to reflux, e.g. 0-100° C.
As in the one-step process, the educt epoxide (1,1-dicarbo substituted oxirane) usually is of the formula II′




wherein A1 is hydrogen or an organic carbon anchor group, and A2 and A3 denote the 1,1-dicarbo substituents, each of which, and the organic carbon anchor group A1, if present, are selected from any organic group able to form a carbon-carbon single bond to the carbon atom No. 1 of the oxirane ring, or carbon atom No. 2 in case of A1. Each of A1, A2, A3 may contain one or more further structures of the type 1,1-dicarbo substituted 2-hydroethylene oxide which are converted in the reaction. In a preferred process, A1 in formula II′ or the below formula II is a carbon anchor group, especially an aryl group, which may carry one or more further structures





or A1 itself is this structure, to be converted in the present process, while no such structures are present in A2 and A3; or is of the formula (I described above. Preferences for residues and educts are as described for the 1-step process (v) described above.

The alpha-hydroxy ketone or alpha-amino ketone formed is preferably a compound of the formula I′




wherein n ranges from 1 to 4;

    D is OH or NR18R19;
    and A1, A2, A3 and R18 and R19 are as defined above. Especially preferred R18 and R19 are methyl. Preferred is an alpha-hydroxykertone product (where D is OH; identical with formula I above).


In step (iii), the reaction is preferably carried out in presence of an aqueous solvent, preferably water or mixtures of water with an organic solvent such as aliphatic or aromatic hydrocarbon, alcohol, ether. Addition of an organic solvent immiscible with water, e.g. hexane, heptane, octane, liquid hydrocarbon fractions like ligroin or petrol ether, benzene, toluene xylene and the like, added before addition of the acid, during the reaction step (iii) or after its completion, may be advantageous for separating the dialcohol product of this step dissolved in the organic phase. The dialcohol product may be isolated, or the whole reaction mixture, preferably the separated organic phase, may be used for the subsequent step (iv).
The acid preferably is a protic acid, advantageously selected from hydrogen halogenides, sulfonic acids, sulfuric acid, acidic hydrogen sulfates, phosphoric acid, carboxylic acids, acidic minerals etc. in water; examples are hydrogen chloride, hydrogen bromide, sulfuric acid, acetic acid, benzoic acid, toluene sulfonic acid, citric acid. Preferably the acid is added to the solution or dispersion of the educt. The amount of acid added preferably ranges from 1 to 20 mol protic hydrogen on 100 mol epoxide.
Temperature often ranges from room temperature to reflux, preferably from 40-100° C.
The oxidizing agent hypochlorite, hypobromite includes, for example, alkaline or alkaline earth or zinc hypochlorites and hypobromites such as LiOCl, NaOCl, KOCl, Ca(OCl)2, LiOBr, NaOBr, KOBr, Ca(OBr)2, Zn(OCl)2, Zn(OBr)2. Most common hypervalent iodine reagents include IBX (1-hydroxy-1,2-benziodoxol-3[1H]-one 1-oxide:




and related iodinanes as described, inter alia, by M. Mülbaier, A. Giannis, ARKIVOC 2003 (vi), 228-236, and publications cited therein.

The oxidizing agent is preferably used in equivalent amounts, relative to the dialcohol to be oxidized, or in excess; examples are 1-20 equivalents of the oxidant per equivalent dialcohol.
The oxidation is preferably carried out in presence of an inert organic solvent such as aliphatic or aromatic hydrocarbons as listed avove for step (iii), or ethers, esters, sulfoxides like dimethylsulfoxide (DMSO).
Further components preferably added include water, catalysts, salts and/or pH stabilizing agents. Examples for catalysts include 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), these components are preferably used in amounts ranging from about 0.1 to 10 mol-% relative to the dialcohol. Further components include alkaline halogenides, hydrogencarbonates like sodium chloride or bromide, sodium hydrogen carbonate, potassium chloride or bromide, potassium hydrogen carbonate.
Catalysts as well as oxidizing agents may be used as such or in immobilized or modified form (e.g. resin-bonded TEMPO or IBX).
The temperature during the oxidation step is preferably kept within the range from −15° C. to about room temperature, preferably from −10 to +15° C.
After completing the oxidation, any aqueous phase, if present, is preferably separated. Remaining excess oxidant may be neutralized using a suitable reducing agent (e.g. sodium dithionite).
General Conditions
As protecting groups Pr, the usual moieties known in the art for the protection of hydroxy functions may be employed. Alcohol protecting moieties include, but are not limited to, hydroxylprotecting groups known in the art (see, for example, Greene, T. W. Protective Groups in Organic Synthesis (Wiley, New York, 1981)). The term includes moieties which can be removed and/or derivatized after the formation of the ketone in accordance with the methods of the invention to yield the free alcohol. Advantageously, the alcohol protecting moiety is inert to the conditions used to generate the ketone. Examples are carbonates such as the benzoxycarbonyl or butyloxycarbonyl (BOC) group, or suitable sulphonyl or acyl residues such as p-toluenesulphonyl (tosyl), phthalyl or trifluoroacetyl, methoxymethyl ethers (MOM), beta-methoxyethoxymethyl ethers (MEM), tetrahydropyranyl ethers (THP), methylthiomethyl ethers (MTM), benzyl groups, and silyl ethers (e.g., trimethyl silyl ethers (TMS), t-butyldimethyl silyl ethers(TBDMS)). Methods of introducing or removing these groups are well known in the art and described, inter alia, in textbooks of organic chemistry or review articles. Furthermore, the term “alcohol protecting moiety” may include alkyl, alkenyl, alkynyl, aralkyl, aryl, and heteroaryl moieties.
Before carrying out the present process steps iii-v, especially primary and secondary alcohol groups within the epoxy educt are advantageously transferred into the group OPr where Pr is the protecting group. Once the desired hydroxyketone or aminoketone has been formed, the alcohol functions may conveniently be recovered by removing the group Pr according to conventional methods. Thus, present invention also pertains to a process wherein

    
    
        v) a 1,1-dicarbo substituted 2-hydro-ethylene oxide, e.g. a compound of the above formula II or II′, containing a substituent OPr, wherein Pr is a protecting group, especially a substituent OPr in CH2—OPr or CH—OPr, is objected to aerobic oxidation in the presence of a transition metal catalyst as explained above, and
        vi) the protecting group is subsequently removed, thus recovering the OH functionality.
    
    


Number indices in residue symbols such as A1, A2, A3, R1, R2, R3, R4 etc. denote the type of residue and not the number of residues attached; in case that more than one residue of this type is attached, the symbol is in brackets and number is indicated by a further number index outside the brackets, for example: (R1)2 denotes 2 residues of the type R1, (R1)3 denotes 3 residues of the type R1, (R2)2 denotes 2 residues of the type R2, (R2)3 denotes 3 residues of the type R2.
In more preferred processes, educts, intermediates and products,

    A1, if n is 1, is phenyl which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, Aro; and/or by C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl or C2-C18alkenyloxy, each of which itself is unsubstituted or substituted by OPr, halogen, NR9R10, carboxy, Aro, COR1, SO2R2, nitro, CN; or is phenyl substituted by O—R8—O—SiR11R12R13; or A1 is C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl or C2-C18alkenyloxy, each of which is unsubstituted or substituted by OPr, halogen, NR9R10, Aro, COR1, OCOR3, NR9COR3, and/or, if containing at least 3 carbon atoms, can be interrupted in a carbon-carbon single bond by O, NR9, COO, CONR9;
    A1, if n is 2, is Ar—R5—Ar; or is a residue R11R12Si(O—R8—O—Ar)2;
    A1, if n is 3, is a residue (Ar)3—R6; or is a residue R11Si(O—R8—O—Ar)3;
    A1, if n is 4, is a residue (Ar)4—R7;
    A2 and A3 independently are C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl; phenyl; C7-C15phenylalkyl; C7-C15cyclohexylalkyl; or one of said residues substituted by OPr, NR9R10, COOH, COR1, SO2R2, halogen, nitro, CN; and/or, if containing at least 3 carbon atoms, are interrupted in a carbon-carbon single bond by O, NR9, COO, OCONR9, CONR9;
    or A2 and A3 together are C4-C11alkylene, -oxaalkylene, -azaalkylene or -alkenylene, each of which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, and/or by a residue selected from C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl, C2-C18alkenyloxy, each of which itself is unsubstituted or substituted by OPr, amino, carboxy, COR1, SO2R2, halogen, nitro, CN;
    where further meanings are as defined for formulae I and II below;
    and especially
    A1, if n is 1, is phenyl which is unsubstituted or substituted by C1-C12alkyl, C1-C12alkoxy, C1-C12alkyl substituted by OPr, C2-C12alkoxy substituted by OPr; or is phenyl substituted by O—R8—O—Si—(CH3)3;
    A1, if n is 2, is a residue phenylene-R5-phenylene; or is a residue (CH3)2Si(O—R8—O-phenylene)2;
    A1, if n is 3, is a residue (phenylene)3-R6; or is a residue CH3Si(O—R8—O-phenylene)3;
    A1, if n is 4, is a residue (phenylene)4-R7;
    A2 and A3 independently are C1-C4alkyl, or together are pentamethylene.


Any aryl usually is C4-C12aryl, especially carbocyclic aryl such as C6-C10aryl including phenyl and naphthyl. Aryl means mostly C6-C12aryl, preferably phenyl or naphthyl, especially phenyl. Aralkyl is usually the alkyl as defined below, which is substituted by the above aryl; preferred is C7-C11phenylalkyl. Alk(yl)aryl is the above aryl substituted by alkyl; preferred is phenyl mono-, di- or trisubstituted by C1-C4alkyl. Ar may be derived from these aryl groups by abstraction of a hydrogen atom from aryl carbon; most preferred Ar is phenylene. Ar moieties may also be interconnected by a tri- or tetravalent spacer R5; in this case, Ar also embraces trivalent aryl, which may be derived from one of the above aryl groups by abstraction of 2 hydrogen atoms from aryl carbon.
Groups which may be unsubstituted or substituted by selected radicals such as C6-C12aryl or C5-C12cycloalkyl, like a phenyl or a cyclohexyl ring, are preferably unsubstituted or mono-, di- or tri-substituted, especially preferred are these groups unsubstituted or mono- or disubstituted.
Halogen usually stands for fluoro, chloro, bromo, iodo; preferred is chloro and bromo, especially chloro.
Alkyl usually is C1-C18alkyl embracing branched and unbranched alkyl, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-ethylbutyl, n-pentyl, isopentyl, 1-methylpentyl, 1,3-dimethylbutyl, n-hexyl, 1-methylhexyl, n-heptyl, isoheptyl, 1,1,3,3-tetramethylbutyl, 1-methylheptyl, 3-methylheptyl, n-octyl, 2-ethylhexyl, 1,1,3-trimethylhexyl, 1,1,3,3-tetramethylpentyl, nonyl, decyl, undecyl, 1-methylundecyl, dodecyl, 1,1,3,3,5,5-hexamethylhexyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl.
Alkoxy stands for alkyl linked over an oxygen atom as spacer: —O-alkyl.
Alkenyl includes, within the scope of the definitions given, inter alia vinyl, allyl, isopropenyl, 2-butenyl, 3-butenyl, isobutenyl, n-penta-2,4-dienyl, 3-methyl-but-2-enyl, n-oct-2-enyl, n-dodec-2-enyl, isododecenyl, n-dodec-2-enyl and n-octadec-4-enyl.
Alkenyloxy stands for alkenyl linked over an oxygen atom as spacer: —O-alkenyl; it often embraces C3-C12alkenyloxy.
Alkyl interrupted by —O—, —NH—, —NR9— and/or by —S— may be interrupted by one or more of the mentioned groups, in each case normally one group being inserted into a bond and hetero-hetero bonds, such as, for example, O—O, S—S, NH—NH etc. not occurring; if the interrupted alkyl is, in addition, substituted, the substituents are not normally in the α-position with respect to the hetero atom. If a plurality of interrupting groups of the type —O—, —NH—, —NR9— and —S— occurs in a radical, those groups are usually identical.
C4-C11alkylene stands for a divalent C4-C11alkyl group wherein the second valency is obtained by abstraction of a hydrogen atom; the term includes “alkylidene”. Oxaalkylene, azaalkylene are alkylene interrupted by oxygen or NR9, as explained above.
Alkenylene includes, within the scope of the definitions given, C2-C12alkylene; the term stands for a divalent alkylene group wherein the second valency is obtained by abstraction of a hydrogen atom; the term includes “alkenylidene”.
A divalent carbocyclic aryl often is phenylene.
Aryloxy stands for aryl linked over an oxygen atom as spacer: —O-aryl, e.g. phenoxy.
Cycloalkyl mainly embraces C5-C12cycloalkyl including cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl and cyclodocecyl. Cyclopentyl, cyclohexyl, cyclooctyl and cyclododecyl are preferred.
Cycloalkenyl mainly embraces C5-C12cycloalkenyl including cyclopentenyl, cyclohexenyl, cycloheptenyl, cyclooctenyl, cyclononenyl, cyclodecenyl, cycloundecenyl and cyclodocecenyl. Cyclohexenyl is preferred.
Cycloalkoxy stands for cycloalkyl linked over an oxygen atom as spacer: —O-cycloalkyl, e.g. cyclohexyloxy.
Cycloalkenoxy stands for cycloalkenyl linked over an oxygen atom as spacer: —O-cycloalkenyl, e.g. cyclohexenyloxy.
R5 is a divalent spacer group covalently bonding the Ar moieties attached; it includes a direct bond; a heteroatomic spacer selected from —O—, —NR9—, —S—, —SO—, SO2—, CO, COO; C1-C18alkylene; C3-C18alkenylene; or C1-C18-alkylene interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO and/or substituted by OPr or NR9R10. Other suitable linkers are 1,3-cyclohexanediyl, 1,4-cyclohexanediyl, 4-methyl-1,3-cyclohexanediyl or are selected from the following structures:




or R5 is a tri- or tetravalent C3-C12alkyl moiety with 2 of its chemical bonds attached to one Ar and its 3rd and, if present, 4th chemical bond attached to the other Ar moiety.

R6 is a trivalent spacer group covalently bonding the Ar moieties attached; it includes C2-C18-alkane-triyl optionally interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, and/or cyclohexylene or phenylene structures, e.g. as listed above for R5, and which is unsubstituted or substituted by OPr or NR9R10; or C3-C18alkene-triyl.
R7 is a tetravalent spacer group covalently bonding the Ar moieties attached; it includes C2-C18-alkane-tetryl optionally interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, and/or cyclohexylene or phenylene structures, e.g. as listed above for R5, and which is unsubstituted or substituted by OPr or NR9R10; or C4-C18alkene-tetryl.
R8 as a divalent aliphatic or cycloaliphatic residue includes C1-C18alkylene; or C3-C36-alkylene interrupted by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO. Other suitable linkers are 1,3-cyclohexanediyl, 1,4-cyclohexanediyl, 4-methyl-1,3-cyclohexanediyl or are selected from the following structures:




In a preferred process, compounds of formulae I and II are those wherein

    A1, if n is 1, is phenyl which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, Aro; and/or by C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl or C2-C18alkenyloxy, each of which itself is unsubstituted or substituted by OPr, halogen, NR9R10, carboxy, Aro, COR1, SO2R2, nitro, CN; or is phenyl substituted by O—R8—O—SiR11R12R13; or A1 is C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl or C2-C18alkenyloxy, each of which is unsubstituted or substituted by OPr, halogen, NR9R10, Aro, COR1, OCOR3, NR9COR3, and/or, if containing at least 3 carbon atoms, can be interrupted in a carbon-carbon single bond by O, NR9, COO, CONR9;
    A1, if n is 2, is Ar—R5—Ar; or is a residue R11R12Si(O—R8—O—Ar)2; A1, if n is 3, is a residue (Ar)3—R6; or is a residue R11Si(O—R8—O—Ar)3;
    A1, if n is 4, is a residue (Ar)4—R7;
    A2 and A3 independently are C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
    phenyl; C7-C15phenylalkyl; C7-C15cyclohexylalkyl; or one of said residues substituted by OPr, NR9R10, COOH, COR1, SO2R2, halogen, nitro, CN; and/or, if containing at least 3 carbon atoms, are interrupted in a carbon-carbon single bond by O, NR9, COO, OCONR9, CONR9;
    or A2 and A3 together are C4-C11alkylene, -oxaalkylene, -azaalkylene or -alkenylene, each of which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, and/or by a residue selected from C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl, C2-C18alkenyloxy, each of which itself is unsubstituted or substituted by OPr, amino, carboxy, COR1, SO2R2, halogen, nitro, CN;
    Ar is phenylene, which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl, C2-C18alkenyloxy, phenoxy;
    R1 is hydrogen, OH, C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
    phenyl, C7-C18alkylphenyl, C1-C18alkoxyphenyl, C1-C18alkoxy, C2-C18alkenoxy, C4-C12cycloalkoxy, C5-C12cycloalkenoxy, phenoxy, C7-C18alkylphenoxy, C7-C18alkoxyphenoxy;
    R2 is OH, C1-C18alkyl or C1-C18alkoxy;
    R3 is C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
    phenyl, C7-C18alkylphenyl, C1-C18alkoxyphenyl;
    R5 is a direct bond; a heteroatomic spacer selected from —O—, —NR9—, —S—, —SO—, SO2—, CO, COO; C1-C18alkylene; C3-C18alkenylene; or C1-C18-alkylene interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene and/or substituted by OPr or NR9R10; or R5 is a tri- or tetravalent C3-C12alkyl moiety with 2 of its chemical bonds attached to one Ar and its 3rd and, if present, 4th chemical bond attached to the other Ar moiety;
    R6 is C2-C18-alkane-triyl optionally interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene, and which is unsubstituted or substituted by OPr or NR9R10; or is C3-C18alkene-triyl;
    R7 is C2-C18-alkane-tetryl optionally interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene, and which is unsubstituted or substituted by OPr or NR9R10; or is C4-C18alkene-tetryl;
    R8 is C1-C18-alkylene, or C3-C36alkylene interrupted by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene;
    R9 and R10 independently are hydrogen, C1-C12alkyl, C1-C12alkyl substituted by OPr, cyclohexyl; or R9 and R10 are joined together to form a pentamethylene or oxapentamethylene moiety;
    R11, R12 and R13 independently are C1-C12alkyl or C1-C12alkoxy;

especially wherein

    A1, if n is 1, is phenyl which is unsubstituted or substituted by C1-C12alkyl, C1-C12alkoxy, C1-C12alkyl substituted by OPr, C2-C12alkoxy substituted by OPr; or is phenyl substituted by O—R8—O—Si—(CH3)3;
    A1, if n is 2, is a residue phenylene-R5-phenylene; or is a residue (CH3)2Si(O—R8—O-phenylene)2;
    A1, if n is 3, is a residue (phenylene)3-R6; or is a residue CH3Si(O—R8—O-phenylene)3;
    A1, if n is 4, is a residue (phenylene)4-R7;
    A2 and A3 independently are C1-C4alkyl, or together are pentamethylene;
    R5 is a direct bond; —O—; —NR9—; CO; C1-C12alkylene; C1-C4-alkylene substituted by OPr or NR9R10; C2-C4alkylene interrupted by —O—, —NR9—; or R5 is a trivalent C3-C12alkyl moiety with 2 of its chemical bonds attached to one phenylene and its 3rd chemical bond attached to the other phenylene moiety;
    R6 is C3-C18-alkane-triyl; or C3-C18alkane-triyl interrupted —O—, —NR9—, COO, CONR9, OCONR9, OCOO; or is C3-C18alkene-triyl;
    R7 is C4-C18-alkane-tetryl; or C4-C18alkane-tetryl interrupted by —O—, —NR9—, COO, CONR9, OCONR9, OCOO, phenylene, cyclohexylene; or is C4-C18alkene-tetryl;
    R8 is C2-C18-alkylene, or C3-C36alkylene interrupted by —O—, —NR9—, COO, CONR9, OCONR9, OCOO, cyclohexylene;
    R9 and R10 independently are hydrogen, C1-C12alkyl; or together are oxapentamethylene;
    R11, R12 and R13 independently are C1-C4alkyl;

each as long as within the specific definitions given for each process step above.



In preferred process steps for the preparation of a hydroxyketone or aminoketone, the epoxide educt used is the one obtained in steps i) and ii) initially described.
Throughout the process steps described, pressure is not critical, the reactions may be carried out, for example, under normal pressure or elevated pressures usual in chemical synthesis, e.g. 0.5-150 bar. Elevated pressures may be advantageous in case that more volatile substances (e.g. dimethyl sulphide, methyl chloride etc. as educt in step i) are employed.
Workup and, if desired, isolation and/or purification of any intermediate or the α-hydroxyketone product may be effected following methods known in the art such as extraction of aqueous phase with organic solvent, drying, crystallization and/or recrystallization (effected, for example, by removing the solvent, cooling, seeding etc.), distillation, chromatography etc.; the procedures given in the examples for these operation may be generalized or replaced by other suitable means of general use in synthetic organic chemistry in laboratory or industrial scale.
Novel Epoxides
Some of the epoxide intermediates used in present invention are novel compounds. Compounds of the formula III




wherein

    n ranges from 2 to 4,
    A1, if n is 2, is Ar—R5—Ar; or is a residue R11R12Si(O—R8—O—Ar)2; or A1 is a direct bond;
    A1, if n is 3, is a residue (Ar)3—R6; or is a residue R11Si(O—R8—O—Ar)3;
    A1, if n is 4, is a residue (Ar)4—R7;
    A2 and A3 independently are C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
    phenyl; C7-C15phenylalkyl; C7-C15cyclohexylalkyl; or one of said residues substituted by OPr, NR9R10, COOH, COR1, SO2R2, halogen, nitro, CN; and/or, if containing at least 3 carbon atoms, are interrupted in a carbon-carbon single bond by O, NR9, COO, OCONR9, CONR9;
    or A2 and A3 together are C4-C11alkylene, -oxaalkylene, -azaalkylene or -alkenylene, each of which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, and/or by a residue selected from C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl, C2-C18alkenyloxy, each of which itself is unsubstituted or substituted by OPr, amino, carboxy, COR1, SO2R2, halogen, nitro, CN;
    Ar is phenylene, which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl, C2-C18alkenyloxy, phenoxy;
    R1 is hydrogen, OH, C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
    phenyl, C7-C18alkylphenyl, C1-C18alkoxyphenyl, C1-C18alkoxy, C2-C18alkenoxy, C4-C12cycloalkoxy, C5-C12cycloalkenoxy, phenoxy, C7-C18alkylphenoxy, C7-C18alkoxyphenoxy;
    R2 is OH, C1-C18alkyl or C1-C18alkoxy;
    R3 is C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
    phenyl, C7-C18alkylphenyl, C1-C18alkoxyphenyl;
    R5 is a direct bond; a heteroatomic spacer selected from —O—, —NR9—, —S—, —SO—, SO2—, CO, COO; C1-C18alkylene; C3-C18alkenylene; or C1-C18-alkylene interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene and/or substituted by OPr or NR9R10; or R5 is a tri- or tetravalent C3-C12alkyl moiety with 2 of its chemical bonds attached to one Ar and its 3rd and, if present, 4th chemical bond attached to the other Ar moiety;
    R6 is C2-C18-alkane-triyl optionally interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene, and which is unsubstituted or substituted by OPr or NR9R10; or is C3-C18alkene-triyl;
    R7 is C2-C18-alkane-tetryl optionally interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene, and which is unsubstituted or substituted by OPr or NR9R10; or is C4-C18alkene-tetryl;
    R8 is C1-C18-alkylene, or C3-C36alkylene interrupted by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene;
    R9 and R10 independently are hydrogen, C1-C12alkyl, C1-C12alkyl substituted by OPr, cyclohexyl; or R9 and R10 are joined together to form a pentamethylene or oxapentamethylene moiety;
    R11, R12 and R13 independently are C1-C12alkyl or C1-C12alkoxy;

and more preferred meanings or any other residue are as defined above for formulae I and II, therefore are another object of the invention.



Examples for compounds obtainable according to the invention include the following:




    
    
        where L, m and n have an average value of about 3;
    
    






    
    
         where p may range, for example, from 2 to 10, such as in compounds of CAS Nos. 163702-01-0; 75980-60-8; 954-16-5; 134-84-9;
    
    









    
    
        where D is C2-C12alkylene, phenylene or cyclohexylene;
    
    






as well as mixtures thereof.

Compounds obtained in the process of present invention can subsequently be further modified following methods known in the art.
Many of the compounds obtainable according to the invention, such as the compounds of the formula I, can be used as photoinitiators for photopolymerization of ethylenically unsaturated compounds or mixtures containing such compounds. Thus, the process of present invention provides a new approach for the preparation of photoinitiators of the alpha-hydroxy ketone and alpha-amino ketone classes.
The α-hydroxy ketone photoinitiators obtainable according to the present invention are, for example, of the formula




    
    
        where
        R11 and R12 independently of one another are hydrogen, C1-C6 alkyl, phenyl, C1-C6 alkoxy, OSiR16(R17)2 or —O(CH2CH2O)q—C1-C6 alkyl, or
        R11 and R12, together with the carbon atom to which they are attached, form a cyclohexyl ring;
        q is a number from 1 to 20;
        R14 is hydrogen, C1-C18 alkyl, C1-C18 alkoxy, —OCH2CH2—OR15, a group CH2═C(CH3)— or is
    
    






    
    
        I is a number from 2 to 10;
        R15 is hydrogen, —COCH═CH2 or —COC(CH3)═CH2; and
        R16 and R17 independently of one another are C1-C8 alkyl or phenyl.
    
    


Compounds of this class are disclosed, for example, in WO03046017, and references cited therein.
Another example of an alpha-hydroxy ketone is a compound of the formula




for example ESACURE® KIP from Fratelli Lamberti, 2-hydroxy-1-{1-[4-(2-hydroxy-2-methylpropionyl)-phenyl]-1,3,3-trimethyl-indan-5-yl}-2-methyl-propan-1-one.

Irgacure® and Darocur® products are available from Ciba Specialty Chemicals Inc.; present α-hydroxy ketone photoinitiator is for example α-hydroxycyclohexylphenyl ketone, available from Ciba Specialty Chemicals as Irgacure® 184.
Abbreviations Used in Specification and Examples:


    TEMPO 2,2,6,6-tetramethyl-4-oxo-piperidine
    Alox aluminum oxide
    Room temperature denotes a temperature in the range 20-25° C.




EXAMPLE 1
Preparation of the Epoxide




A mixture of 586 g (4.6 mol) benzyl chloride and 418 g (4.6 mol) tetrahydrothiophene in 1 L water is heated to 85° C. with stirring until a clear and homogen, or slightly hazy single phased solution is obtained. This solution is cooled to 20° C. and added dropwise to a reaction mixture consisting of 1104 g of 50% NaOH (13.8 mol) and 935 g of acetone (16.1 mol) in 250 g of methanol. After the addition, the reaction mixture is kept without stirring for 10 min. for phase separation. After separation of the organic phase, the product is isolated by distillation, yielding 750 g of the desired crude product, which is used for the next reaction step without further purification.
EXAMPLE 2




A mixture of 610 g (50-60% b.w. solution in water, 2.3 mol) of the crude epoxide from example 1 and 68 g (0.324 mol) citric acid in 1.7 litres of water is heated to 80° C. and stirred at this temperature until no educt can be found any more by thin layer chromatography (ca. 6 h). 1.5 l of heptane are then added at 80° C., the mixture is stirred for 10 minutes and then allowed to separate for another 10 min. The organic phase is cooled to 0° C. and precipitation is induced by addition of a seeding crystal. 250 g (65%) of the diol are obtained.




A solution of 3.5 g (29.7 mmol) KBr in 50 ml water is added to a solution of 50 g (0.297 mol) of the diol obtained in part (a) in 300 ml of toluene. Then 0.9 g (5.76 mmol) TEMPO is added. The reddish suspension is cooled to 0° C. 160 ml of a 12% solution of sodium hypochlorite (0.3 mol) is added with maintaining the internal temperature at 5° C. or lower. The mixture is subsequently stirred for 1 h at 0-5° C. and then allowed to separate for 10 min. 400 ml of sodium dithionite solution (obtained from 30 g sodium dithionite (85%) and 400 ml of water) is added to the organic phase and stirred at 85° C. for 1-2 h. The organic phase is again separated and concentrated (rotavap). The crude product is then subjected to fractional distillation, yielding 42.5 g (87%) of the desired product as a colourless oil.
EXAMPLE 3




A mixture of 56 mg (0.25 mmol) Pd-acetate and 90 mg (0.25 mmol) bathocuproin in 50 mL of water is stirred for 24 h at room temperature. Subsequently, 741 mg (5 mmol) of the epoxide obtained in example 1 are added. The reaction mixture is stirred at 100° C. for 48 h under oxygen atmosphere. After evaporation, the residue is filtered over Alox and the crude product purified by chromatography (hexane:ethyl acetate 6:1), yielding 386 mg of the desired product.
EXAMPLE 4
Preparation of Epoxide




A mixture of 500 g (3.1 mol) of p-chlorobenzyl chloride and 282 g (3.1 mol) of tetrahydrothiophene in 0.78 L of water is heated at 85° C., whilst stirring well, until a homogeneous clear or slightly turbid single-phase solution has been obtained. The solution is then cooled to 20° C. and is slowly added dropwise to a reaction mixture consisting of 992 g of 50% sodium hydroxide solution (12.4 mol) and 720 g of acetone (12.4 mol) in 195 g of methanol. After the addition is complete, the reaction mixture is allowed to stand for 10 minutes until the phases have separated. The organic phase is separated off and the product obtained by distillation. 400 g of the desired product is obtained in the form of a clear colourless liquid.
EXAMPLE 5




EXAMPLE 6




A mixture of 27 mg (0.12 mmol) of palladium acetate and 43 mg (0.12 mmol) of bathocuproine in 23 mL of water is stirred at room temperature for 24 hours. 420 mg (2.3 mmol) of epoxide (product of example 4) are then added and the reaction mixture is stirred at 100° C. under an oxygen atmosphere for 48 hours. The reaction mixture is concentrated by evaporation, the residue is filtered over Alox, and the desired product is isolated after chromatography on silica gel (hexane:ethyl acetate 6:1).
EXAMPLE 7
Preparation of Epoxide




A mixture of 90 g (0.35 mol) of p-bromobenzyl chloride and 32 g (0.35 mol) of tetrahydrothiophene in 0.2 L of water is heated at 80° C., whilst stirring well, until a homogeneous clear or slightly turbid single-phase solution has been obtained. The solution is cooled to 60° C. and is slowly added dropwise to a reaction mixture, cooled to 15° C., consisting of 113 g of aqueous sodium hydroxide solution (50%, 1.41 mol) and 82 g of acetone (1.41 mol) in 30 mL of methanol. After the addition is complete, the reaction mixture is allowed to stand for about 10 minutes until the phases have separated. The organic phase is separated off and the product isolated by distillation. Yield: 58 g (73%) of epoxide in the form of a clear colourless liquid.
EXAMPLE 8




EXAMPLE 9




A mixture of 30 mg (0.135 mmol) of palladium acetate and 49 mg (0.135 mmol) of bathocuproine in 27 mL of water is stirred at room temperature for 24 hours. 609 mg (2.68 mmol) of epoxide (product of example 7) are then added and the reaction mixture is stirred at 100° C. under an oxygen atmosphere for 48 hours. The reaction mixture is concentrated by evaporation, the residue is filtered over Alox, and the desired product is obtained after chromatography on silica gel (hexane:ethyl acetate 6:1).
EXAMPLE 10
Preparation of Epoxide




56 g (0.367 mol) of p-fluorobenzyl chloride, 33.4 g (0.367 mol) of tetrahydrothiophene and 0.1 L of water are heated at 85° C., whilst stirring well. After about 3 hours there is formed, from the two-phase reaction mixture, a homogeneous clear or slightly turbid single-phase solution of the corresponding sulphonium salt. The solution obtained is cooled to 25° C. and is slowly added, with stirring, to a mixture, cooled to 15° C., of 118 g of aqueous sodium hydroxide solution (50%, 1.47 mol) and 86 g of acetone (1.47 mol) in 25 mL of methanol. The mixture obtained is allowed to stand for about 10 minutes until the phases have separated; the organic phase is separated off and the product isolated by vacuum distillation. 45.2 g (74%) of the product are obtained in the form of a clear colourless liquid.
EXAMPLE 11




EXAMPLE 12




The reaction is carried out following the method of example 6, using the product of example 10 as starting material.
EXAMPLE 13
Preparation of Epoxide




A mixture of 152 g (1.18 mol) of benzyl chloride, 108 g (1.18 mol) of tetrahydrothiophene and 0.225 L of water is stirred well at 85° C. until a homogeneous clear or slightly turbid single-phase solution of S-benzyltetrahydrothiophenium chloride has been obtained. The solution is cooled to 20° C. and is slowly added dropwise to a reaction mixture consisting of potassium hydroxide solution (prepared from 267 g (4.75 mol) of potassium hydroxide in 0.53 L of ice-water) and 467 g of cyclohexanone (4.75 mol) in 225 g of methanol. After the addition is complete, the reaction mixture is allowed to stand for 10 minutes until the phases have separated; the organic phase is separated off and subjected to fractional distillation. 181 g (80%) of 2-phenyl-1-oxa-spiro[2.5]octane are obtained in the form of a clear colourless oil.
EXAMPLE 14




EXAMPLE 15




A mixture of 0.112 g (0.5 mmol) of palladium acetate and 0.018 g (0.5 mmol) of bathocuproine in 100 mL of water is stirred at room temperature for 24 hours. 1.88 g (10 mmol) of epoxide (product of example 13) are then added and the reaction mixture is stirred at 100° C. under an oxygen atmosphere for 48 hours. After cooling to room temperature, the product is extracted twice using 150 mL of ethyl acetate each time. The combined organic phases are dried over sodium sulphate and concentrated by evaporation, and the crude product is chromatographed on silica gel (hexane:ethyl acetate 9:1). The desired product is obtained in the form of a light-yellow oil.
EXAMPLE 16
Preparation of Epoxide




A mixture of 90 g (0.503 mol) of 1,3-bis(chloromethyl)benzene (α,α′-dichloro-m-xylene) and 91.4 g (1.0 mol) of tetrahydrothiophene in 0.18 L of water is heated at 85° C., whilst stirring well, until a homogeneous clear or slightly turbid single-phase solution has been obtained. The solution is cooled to room temperature and is slowly added dropwise, with stirring, to a reaction mixture of 320 g of aqueous sodium hydroxide solution (50%, 4.0 mol) and 233 g of acetone (4.0 mol) in 45 mL of methanol. After the addition is complete, the reaction mixture is allowed to stand for 10 minutes until the phases have separated. The organic phase is separated off and the product 1,3-bis-epoxybenzene obtained by distillation in the form of a yellow oil.
EXAMPLE 17




EXAMPLE 18




A mixture of 45 mg (0.2 mmol) of palladium acetate and 72 mg (0.2 mmol) of bathocuproine in 20 mL of water is stirred at room temperature for 24 hours. 437 mg (2.0 mmol) of epoxide (product of example 16) are then added and the reaction mixture is stirred at 100° C. under an oxygen atmosphere for 40 hours. After cooling to room temperature, the product is extracted three times using 50 mL of chloroform each time. The combined organic phases are dried over sodium sulphate and concentrated by evaporation, and the desired product is obtained after chromatography on silica gel (hexane:ethyl acetate 9:1).

## Claims

1. Process for the preparation of an alpha-hydroxy ketone of the formula I




by converting a 1,1-dicarbo substituted oxirane of the formula II




wherein n ranges from 1 to 4;
A1, if n is 1, is carbocyclic aryl which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, Aro, and/or by alkyl, alkoxy, alkenyl or alkenyloxy, each of which itself is unsubstituted or substituted by OPr, halogen, NR9R10, carboxy, Aro, COR1, SO2R2, nitro, CN; or is carbocyclic aryl substituted by O—R8—O—SiR11R12R13;
A1, if n is 2, is Ar—R5—Ar; or is a residue R11R12Si(O—R8—O—Ar)2;
A1, if n is 3, is a residue (Ar)3—R6; or is a residue R11Si(O—R8—O—Ar)3;
A1, if n is 4, is a residue (Ar)4—R7;
A2 and A3 independently are alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, alkylaryl, arylalkyl, cycloalkylalkyl, or one of said residues substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN; and/or, if having at least 3 carbon atoms, are interrupted in a carbon-carbon single bond by O, NR9, COO, OCONR9, CONR9;
or A2 and A3 together are C4-C11alkylene, -oxaalkylene, -azaalkylene or -alkenylene, each of which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, and/or by alkyl, alkoxy, alkenyl, alkenyloxy, each of which itself is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN;
Ar stands for a divalent carbocyclic aryl which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, Aro, alkyl, alkoxy;
Aro stands for aryloxy which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, alkyl, alkoxy, alkenyl, alkenyloxy;
Pr stands for hydrogen or a protecting group;
R1 is hydrogen, OH, alkyl, alkenyl, cycloalkyl, cycloalkenyl, phenyl, alkylphenyl, alkoxyphenyl, alkoxy, alkenoxy, cycloalkoxy, cycloalkenoxy, phenoxy, alkylphenoxy, alkoxyphenoxy;
R2 is OH, alkyl or alkoxy;
R3 is alkyl, alkenyl, cycloalkyl, cycloalkenyl, phenyl, alkylphenyl, alkoxyphenyl;
R4 and R′4 independently are hydrogen, C1-C12alkyl or cyclohexyl;
R5 is a direct bond; a heteroatomic spacer selected from —O—,—NR9—,—S—,—SO—, SO2—,CO, COO; C1-C16alkylene; C3-C18alkenylene; or C1-C18-alkylene interrupted or end-capped by —O—,—NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene and/or substituted by OPr or NR9R10; or R5 is a tri- or tetravalent C3-C12alkyl moiety with 2 of its chemical bonds attached to one Ar and its 3rd and, if present, 4th chemical bond attached to the other Ar moiety;
R6 is C2-C18-alkane-triyl optionally interrupted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene, and which is unsubstituted or substituted by OPr or NR9R10; or is C3-C18alkene-triyl;
R7 is C2-C18-alkane-tetryl optionally interruppted or end-capped by —O—, —NR9—, —S—, —SO—, SO2—CO, COO, CONR9, OCONR9, OCOO, cyclohexylene, phenylene, and which is unsubstituted or substituted by OPr or NR9R10; or is C4-C18alkene-tetryl;
R8 is a divalent aliphatic or cycloaliphatic residue;
R9 and R10 independently are hydrogen, C1-C12alkyl, C1-C12alkyl substituted by OPr and/or NR4R′4, C5-C12cycloalkyl; or R9 and R10 are joined together to form a tetramethylene, pentamethylene, oxatetramethylene or oxapentamethylene moiety;
R11, R12 and R13 independently are C1-C12alkyl or C1-C12alkoxy;
wherein the 1,1-dicarbo substituted oxirane is subjected to aerobic oxidation in the presence of water and in the presence of a transition metal catalyst selected from a group consisting of Pd, Ru, Cu, Fe, Mn, Co, Mo, W, V, Ti, Ta, and Pt catalysts;
wherein the transition metal catalyst is a complex having an organic chelating ligand bonded to the transition metal as central atom.

2. The process of claim 1 wherein the aerobic oxidation is effected by the presence of gaseous oxygen and/or a molecular oxygen releasing agent.

3. The process of claim 1 wherein the transition metal catalyst is a Pd catalyst.

4. The process of claim 1 wherein the alpha-hydroxy ketone contains a substituent OPr, wherein Pr is a protecting group, which is subsequently removed, thus recovering the OH functionality.

5. The process of claim 1 , wherein
A1, if n is 1, is phenyl which is unsubstituted or substituted by OPr, NR9R10carboxy, COR1, SO2R2, halogen, nitro, CN, Aro; and/or by C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl or C2-C18alkenyloxy, each of which itself is unsubstituted or substituted by OPr, halogen, NR9R10carboxy, Aro, COR1, SO2R2, nitro, CN; or is phenyl substituted by O—R8—O—SiR11R12R13; or A1is C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl or C2-C18alkenyloxy, each of which is unsubstituted or substituted by OPr, halogen, NR9R10, Aro, COR1, OCOR3, NR9COR3, and/or, if havinq at least 3 carbon atoms, can be interrupted in a carbon-carbon single bond by O , NR9, COO, CONR9;
A1, if n is 2, is Ar—R5—Ar; or is a residue R11R12Si(O—R8—O—Ar)2; or Alis a direct bond;
A1, if n is 3, is a residue (Ar)3—R6; or is a residue R11Si(O—R8O—Ar)3;
A1, if n is 4, is a residue (Ar)4—R7;
A2 and A3 independently are C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
phenyl; C7-C15phenylalkyl; C7-C15cyclohexylalkyl; or one of said residues substituted by OPr, NR9R10, COOH, COR1, SO2R2, halogen, nitro, CN; and/or, if havinq at least 3 carbon atoms, are interrupted in a carbon-carbon single bond by O, NR9, COO, OCONR9, CONR9;
or A2 and A3 together are C4-C11alkylene, -oxaalkylene, -azaalkylene or -alkenylene, each of which is unsubstituted or substituted by OPr, NR9R10, carboxy, COR1, SO2R2, halogen, nitro, CN, and/or by a residue selected from C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl, C2-C18alkenyloxy, each of which itself is unsubstituted or substituted by OPr, amino, carboxy, COR1, SO2R2, halogen, nitro, CN;
Ar is phenylene, which is unsubstituted or substituted by OPr, NR9R10,carboxy, COR1, SO2R2, halogen, nitro, CN, C1-C18alkyl, C1-C18alkoxy, C2-C18alkenyl, C2-C18alkenyloxy, phenoxy;
R1 is hydrogen, OH, C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
phenyl, C7-C18alkylphenyl, C1-C18alkoxyphenyl, C1-C18alkoxy, C2-C18alkenoxy, C4-C12cycloalkoxy, C5-C12cycloalkenoxy, phenoxy, C7-C18alkylphenoxy, C7-C18alkoxyphenoxy;
R2 is OH, C1-C18alkyl or C1-C18alkoxy;
R3 is C1-C18alkyl; C2-C18alkenyl; C4-C12cycloalkyl; C5-C12cycloalkenyl;
phenyl, C7-C18alkylphenyl, C1-C18alkoxyphenyl;
R8 is C1-C18-alkylene, or C3-C36alkylene interrupted by —O—, —NR9—, —S—, —SO—, SO2—, CO, COO, CONR9, OCONR9, OCOO, cyclohexylene;
R9 and R10 independently are hydrogen, C1-C12alkyl, C1-C12alkyl substituted by OPr, cyclohexyl; or R9 and R10 are joined together to form a pentamethylene or oxapentamethylene moiety;
R11, R12 and R13 independently are C1-C12alkyl or C1-C12alkoxy.

6. The process of claim 1, wherein
A1, if n is 1, is phenyl which is unsubstituted or substituted by C1-C12alkyl, C1-C12alkoxy, C1-C12alkyl substituted by OPr, C2-C12alkoxy substituted by OPr; or is phenyl substituted by O—R8—O—Si—(CH3)3;
A1, if n is 2, is a residue phenylene-R5-phenylene; or is a residue (CH3)2Si(O—R8—O-phenylene)2;
A1, if n is 3, is a residue (phenylene)3-R6; or is a residue CH3Si(O—R8-O-phenylene)3;
A1, if n is 4, is a residue (phenylene)4-R7;
A2 and A3 independently are C1-C4alkyl, or together are pentamethylene;
R5 is a direct bond; —O—; —NR9—; CO; C1-C12alkylene; C1-C4-alkylene substituted by OPr or NR9R10; C2-C4alkylene interrupted by —O—, —NR9—; or R5 is a trivalent C3-C12alkyl moiety with 2 of its chemical bonds attached to one phenylene and its 3rd chemical bond attached to the other phenylene moiety;
R6 is C3-C18-alkane-triyl; or C3-C18alkane-triyl interrupted —O—, —NR9—, COO, CONR9, OCONR9, OCOO; or is C3-C18alkene-triyl;
R7 is C4-C18-alkane-tetryl; or C4-C18alkane-tetryl interrupted by —O—, —NR9—, COO, CONR9, OCONR9, OCOO, phenylene, cyclohexylene; or is C4-C18alkene-tetryl;
R8 is C2-C18-alkylene, or C3-C36alkylene interrupted by —O—, —NR9—, COO, CONR9, OCONR9, OCOO,cyclohexylene;
R9 and R10 independently are hydrogen, C1-C12alkyl; or together are oxapentamethylene;
R11, R12 and R13 independently are C1-C4alkyl.