PROCESS FOR PREPARING ESTERS OF ALKANOIC ACIDS VIA REARRANGEMENT OF ALPHA-HALOKETALS

Abstract: Process for preparing esters of alkanoic acids via re­ arrangement of alpha-haloketals in the presence of a Lewis acid. The reaction is preferably carried out in the presence of catalytic amounts of a Lewis acid and of a diluent at a tempera­ ture in the range from about 0° to the reflux temperature of the diluent. The esters thus obtained are useful as intermediate pro­ ducts for preparing drugs. The process involves the preparation of new alpha-­ haloketals.

Description: This invention relates to a new process for preparing esters of alkanoic acids via rearrangement of alpha-haloketals in the presence of a Lewis acid excluding Ag⁺. More particularly, the new process of this invention is represented by the following scheme: wherein R is selected from the group comprising an aryl, a substituted aryl, a fused heterocyclic aryl, a heterocyclic, a substituted heterocyclic and a fused aryl-heterocyclic radical; provided however, that R is not 6-methoxy-2-naphthyl- and 5-bromo-6-methoxy-2-naphthyl radical; R' is selected from the group comprising an alkyl radical having from 1 to 6 carbon atoms and a benzyl radical; R'' is selected from the group comprising an alkyl radical having from 1 to 6 carbon atoms and a benzyl radical; R'and R'', together, are an alkylene radical having from 2 to 6 carbon atoms which, together with the group, forms a heterocyclic ring; X is a halogen atom; R''' is selected from the group comprising a hydrogen atom, an alkyl having from 1 to 6 carbon atom, an aryl, a substituted aryl, a fused heterocyclic-aryl, a heterocyclic, a substituted heterocyclic, a fused aryl-heterocyclic radical; Y is selected from the group comprising an alkyl radical having from 1 to 6 carbon atoms, a halo-alkyl radical having from 2 to 6 carbon atoms and a benzyl radical. The esters of general formula II may be hydrolized by conventional procedures to afford the corresponding alkanoic acids which are useful as such or as intermediate products; many of them are useful as drugs. More particularly many members of this class are known to be useful as anti-inflammatory, analgesic and antipyretic agents; examples of such compounds include ibuprofen, fenclorac, indoprofen, flurbiprofen, naproxen, ketoprofen, fenoprofen, piroprofen, suprofen, aclofenac, xenbucin, diclofenac and tolmetin (Anti-Inflammatory Drugs, Springer Verlag, 1979, pages 321-3). Other members of this class, such as thienyl acetic acid, are useful as intermediate products for preparing semisynthetic penicillins and cephatosporins or for preparing anti-inflammatory drugs such as thiaprofenic acid. The most part of the known synthetic routes for preparing alpha aryl-alkanoic acids involves the substitution of the aromatic ring with an acyl radical because this substitution may be carried out in high yields and with a high positional selectivity. The subsequent step is consisting in the transformation of the acyl moiety into the alkanoic moiety via Darzen reaction, via a variation of Wittig reaction which comprises the use of methoxycarbenylides instead of carbenylides, via Grignard reaction, via cyanidrine or via reduction to alcohol, subsequent halogenation and treatment with a cyanide or carbon monoxide. All of the above mentioned procedures present many drawbacks because they involve many steps, the yields are usually low and the reagents are expensive and highly polluting. In consideration of what above, many efforts have been made to prepare aryl-alkanoic acids via rearrangement of the acyl-derivatives. A known oxidative rearrangement is the Willgerodt reaction, but it is of industrial value only for preparing arylacetic acids from arylmethyl-ketones and it does not allow to achieve good yields because of the many purifications that are needed for eliminating the sulfur-containing by-products. British patent 1.535.690 describes a process which comprises (i) the acylation of an aromatic hydrocarbon (ii) the reaction of the ketone thus obtained to prepare the corresponding ketal (iii) the generation of an enol ether from the corresponding ketal (iv) the rearrangement of the enol ether with thallium ions in an organic liquid containing, per equivalent of the enol ether at least one equivalent of a nucleophilic compound. This process suffers the disadvantage that thallium can react with the aromatic moiety to form some by-products. The alkanoic acids, prepared according to this synthetic route, contain always traces of thallium as metal and/or as metal-organic product and are potentially dangerous because of the very high toxycity of thallium. Surprisingly, it has been now found that Lewis acids (J. March-Advanced Organic Chemistry, McGraw-Hill and Kogakusha e., 2 edt., 236-8; Chem. Rev., 75 , No. 1, 1-20) act as catalysts in preparing esters of formula II via rearrangement pathway of ketals of formula I. In order to obtain the rearrangement, the process is carried out in such a way that the catalyst exerts a good affinity toward the halogen atom and a poor affinity toward the oxygen atoms of the ketal group in the alpha-halo-ketal (I). Meantime, it must be avoided such a condition that catalyst acts as a reducing agent and transforms alpha-halo-ketals (I) into ketals and/or ketones. Catalyst that may be used according to this invention are the organic salts, such as acetate, propionate, benzoate, trifluoromethane sulphonate, methane sulphonate, etc. as well as the inorganic salts such as chloride, bromide, iodide, sulphate etc of Copper, Magnesium, Calcium, Zinc, Cadmium, Barium, Mercury, Tin, Antimony, Bismuth, Manganese, Iron, Cobalt, Nickel and Palladium. A preferred embodiment of this invention contemplates the use of metal halides such as ZnCl₂, CoCl₂, ZnBr₂, SnCl₂, FeCl₂, FeCl₃, NiBr₂, CdCl₂, MgCl₂, HgCl₂, Hg₂Cl₂, SbCl₃, BaCl₂, CaCl₂, CuCl, CuCl₂, MnCl₂, SnCl₄, BiCl₃, PdCl₂. The catalyst may be introduced directly into the reaction medium; alternatively, it is formed "in situ". The catalyst is preferably used in catalytic amount; larger quantities do not afford appreciable advantages. The rearrangement according to this invention is preferably carried out in the presence of a suitable diluent. Examples of such diluents are the aliphatic halo-hydrocarbons, aliphatic cyclic-hydrocarbons, lower alcohols, aliphatic acids and their esters, aromatic hydrocarbons and halo aromatic hydrocarbons such as dicloroethane, trichloroethane, chlorobenzene, toluene, methylene chloride, methanol, trimethyl orthoformate, and their mixtures. The rearrangement contemplated by this invention is conducted at a temperature in the range from about 0°C to the reflux temperature of the diluent. Considering that either ketals (I) or esters (II) are stable at high temperature, a preferred embodiment of this invention contemplates the use of high boiling diluents. The reaction time differs according to the ketal reactivity, the catalyst activity and the reaction temperature; so it is very wide and it is comprised in the range from about ½ hour to about 160 hours. The meaning of Y in the general formula II is related to the nature of the ketal and/or the diluent. When R' and R'' are alkyl radicals or benzyl radicals and the diluent is not a nucleophilic compound, Y has the same meaning of R' and R''. When an alcohol is used as diluent it may also take part in the esterification and/or transesterification step by forming esters of general formula II wherein Y is the alkyl radical of the alcohol used as diluent. When an alkylene-alpha-halo-ketal (I) is rearranged, then Y (in the ester II) may be an halo-alkyl-radical because the halogen atom (X in formula I) replaces one oxygen atom of the starting ketal. Furthermore, scrambling between the anion of the metal salt and the halogen-atom (X in formula I) may take place during the rearrangement step so that the anion of the metal salt may be present as substituent instead of X in the radical Y. The halo-ketals (I) are prepared in an easy way and in high yields from the corresponding ketones either (i) by halogenation of the ketone and subsequent ketalization of the thus obtained alpha-halo-ketone or (ii) by ketalization of the ketone and subsequent halogenation of the thus obtained ketal. The ketalization step may be carried out according to conventional procedures by means of an alcohol in the presence of an acid catalyst and of an ortho ester. When the ketal is prepared from a glycol, the water which is formed during the reaction is usually removed by azeotropic distillation for example with benzene, toluene, xylene, tetrachloroethane. The introduction of the halogen-atom in alpha position of carbonyl group or of ketal group may be carried out by means of conventional reagents such as sulfuryl chloride, cupric chloride, cupric bromide, N-bromo-succinamide, pyridine or pyrrolidone-perbromide hydrobromide. The halogenation step, the ketalization step and the rearrangement of alpha-halo-ketals of general formula I can be carried out in the same reaction vessel without isolating any intermediate product and in the presence of the same diluent. The ketones that are used as starting materals according to this invention may be prepared according to the Friedel-Crafts reaction. The ketals of general formula I wherein R''' is an alkyl radical; R is a substituted aryl, a fused heterocyclic-aryl, a heterocyclic, a substituted heterocyclic and a fused aryl-heterocyclic radical; provided, however, that R is not 6-methoxy-2-naphthyl and 5-bromo-6-methoxy-2-naphthyl radical; R', R'' and X have the above mentioned meaning with the proviso, that R is not 4-alkylthiophenyl if R' and R'' are selected from an alkyl radical and X is a bromine atom, are new and, therefore, they are a further object of this invention. Examples of such compounds include: 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)- 1,3-dioxolane 2-(1'-chloro-ethyl)-2-(4'-isobutyl-phenyl)-1,3-dioxolane 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)-1,3-dioxane 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)-4,5-dimethyl-1,3-dioxolane 2-bromo-1-(4'-isobutyl-phenyl)-1,1-dimethoxy-propane 2-(1'-bromoethyl)-2-(4'-propionamido-phenyl)-1,3-dioxolane 2-(1'-bromoethyl)-2-(4'-phthalimido-phenyl)-1,3-dioxolane 2-(1'-bromoethyl)-2-(2-fluoro-4-diphenylyl)-1,3-dioxolane 2-bromo-1,1-dimethoxy-1-(2'-thienyl)-propane 2-(1'-bromo-propyl)-2-(4-diphenylyl)-1,3-dioxolane. The following specific description is given to enable those skilled in this art to more clearly understand and practice the present invention. It should not be considered as a limitation upon the scope of the invention but merely as being illustrative and representative thereof. For all the examples I.R. spectra have been recorded in nujol/NaCl; whereas N.M.R. spectra have been recorded with a 60 MHz spectrometer. The chemical shifts have been expressed in delta [ppm]. Preparation Examples a) 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)-1,3-dioxolane (A) 2-bromo-1-(4'-isobutyl-phenyl)-propan-1-one (67.5 g, 0.250 mol), ethylene glycol (78 g, 1.26 mol), para-toluenesulfonic acid hydrate (2.4 g, 12.6 mmol) and toluene (80 ml) are heated and stirred together for 5 h in a flask beneath a Dean-Stark trap. The reaction mixture is added dropwise to a well stirred saturated sodium carbonate solution (1l) and extracted with toluene (2×100 ml). The combined organic solution is washed with a 2% sodium hydrogen carbonate solution, dried (Na₂CO₃), filtered and concentrated in vacuo to give the desired ketal as oil (77.3 g, 0.247 mol; yield 99%). I.R.: C=O stretching is absent; no band is present in the 2.5-3.2 microns region. N.M.R. (CCl₄/TMS): 0.89 (d, 6H, J=6Hz); 1.48 (d, 3H, J=7Hz); 1.85 (m, 1H, J=6Hz); 2.43 (d, 2H, J=6Hz); 2.43 (d, 2H, J=6Hz); 4.00 (m, 5H); 6.9-7.9 (AA'BB', 4H). b) 2-(1'-chloro-ethyl)-2-(4'-isobutyl-phenyl)-1,3-dioxolane (B) A solution of CuCl₂ (13.5 g, 100 mmol), LiCl (3.2 g, 76 mmol), 4'-isobutyl-propiophenone (9.33 g, 49 mmol) in DMF (40 ml) is kept at 83°C for 3 h. The solution is poured into a 3% hydrochloric acid, extracted with toluene. The organic extract is washed with water and the solvent is removed in vacuo. The residue is crystallized from methanol to give the desired chloroketone (6.35 g, 28.3 mmol, yield 58%) as analytically pure product, m.p. 53.5-54.5°C. I.R.: C=O stretching 5.95 microns N.M.R.: (CCl₄/TMS) 0.89 (d, 6H, J=7Hz); 1.75 (d, 3H, J=7Hz); 2.53 (d, 2H, J=7Hz); 5.20 (q, 1H, J=7Hz); 7.1-8.1 (AA'BB', 4H). Following the procedure of Example 1a the ketal B is prepared Reagents: 2-chloro-4'-isobutyl-propionphenone (26 g, 116 mmol) above prepared, ethylene glycol (36 g, 0.58 mol). Catalyst: para-toluenesulfonic acid hydrate (1.1 g, 5.78 mmol). Solvent: Toluene (40 ml) Reaction time: 4 h Yield: 29.6 g, 110 mmol, 95% as oil I.R.: C=O stretching is absent; no band is present in the 2.5-3.2 microns region. N.M.R.: (CCl₄/TMS): 0.89 (d, 6H, J=6Hz); 1.30 (d, 3H, J=7Hz); 1.82 (h, 1H, J=6Hz); 2.41 (d, 2H, J=6Hz); 3.89 (m, 5H); 6.9-7.4 (AA'BB', 4H). c) 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)-1,3-dioxane (C) Is prepared according to the procedure of Example 1a Reagents: 2-bromo-1-(4'-isobutyl-phenyl)-propan-1-one (13.5 g, 50 mmol); 1.3 propanediol (19 g, 250 mmol). Catalyst: para-toluenesulfonic acid hydrate (0.5 g, 2.6 mmol) Solvent: Toluene (50 ml) Reaction time: 16 h Yield: 16.05 g, (49 mmol; 98%) as oil I.R.: C=O stretching is absent; no band is present in the 2.5-3.2 microns region N.M.R: (CCl₄/TMS): 0.89 (d, 6H, J=6Hz); 1.43 (d, 3H, J=7Hz); 1.1-2.3 (m, 3H); 2.42 (d, 2H, J=6Hz); 3.75 (m, 5H); 6.9-7.4 (AA'BB', 4H). d) 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)-4,5-dimethyl-1,3-dioxolane (D) Is prepared according to the procedure of Example 1a. Reagents: 2-bromo-1-(4'-isobutyl-phenyl)-propan-1-one (13.5 g, 50 mmol); 2,3-butanediol (112.5 g, 1.25 mol). Catalyst: para-toluenesulfonic acid hydrate (0.5 g, 2.6 mmol) Solvent: Toluene (50 ml) Reaction time: 14 h Yield: (17.05 g, 50 mmol, 100%) as oil I.R.: C=O stretching is absent; no band is present in the 2.5-3.2 microns region. N.M.R. (CCl₄/TMS):0.89 (d, 6H, J=6Hz); 1.1-2.3 (m, 10H), 2.40 (d, 2H, J=6Hz); 4.06 (m, 3H); 6.9-7.4 (AA'BB', 4H). e) 2-bromo-1-(4'-isobutyl-phenyl)-1,1-dimethoxy-propane (E) Bromine (160 g, 1 mol) is added dropwise to a well stirred solution of 4'-isobutyl-propionphenone (190 g, 1 mol) in chloroform (500 ml), kept at 15°C. The solution is stirred for additional 2 h. It is poured into wafer and the organic layer is washed with water and with a saturated sodium hydrogen carbonate solution. It is dried (Na₂SO₄), filtered and concentrated in vacuo to give 2-bromo-4'-isobutyl-propiophenone (263 g, 0.98 mol, yield 98%). An analytically pure sample is prepared by crystallization from methanol: m.p. 65-67°C. I.R.: C=O stretching 5.26 microns N.M.R. (CCl₄/TMS): 0.89 (d, 6H, J=6Hz), 1.85 (m, 4H); 2.53 (d, 2H, J=7Hz); 5.17 (q, 1H, J=6Hz); 7.1-8.1 AA'BB', 4H). A solution of 2-bromo-4'-isobutyl-propiophenone (5.4 g, 20 mmol), thus obtained, trimethyl orthoformate (6.54 g, 62 mmol), methanesulfonic acid (0.4 ml) and of methanol (65 ml) is kept at 50°C for 24 h. The solution is poured, under vigorous stirring, into a saturated sodium carbonate solution (0.2 l), extracted with toluene (2×150 ml). The combined organic extract is washed with a 2% sodium hydrogen carbonate solution. Evaporation of the solvent in vacuo leaves an oil consisting of ketal L (5.04 g, 16 mmol; yield 80%). N.M.R. (CCl₄/TMS): 0.89 (d, 6H, J=6Hz); 1.45 (d, 3H, J=7Hz); 1.85 (m, 1H, J=6Hz); 2.43 (d, 2H, J=6Hz); 3.10 (s, 3H); 3.30 (s, 3H); 4.30 (q, 1H, J=7Hz); 6.9-7.4 (AA'BB', 4H). f) 2-bromo-1,1-dimethoxy-1-(4'-methoxy-phenyl)-ethane (F) A solution of 2-bromo-1-(4'-methoxy-phenyl)-ethanone (22.9 g, 0.1 mol), trimethyl orthoformate (25 g, 0.236 mol), methanesulfonic acid (0.73 g, 0.0076 mol) and methanol (100 ml) is kept at 60°C for 3 h. The solution is poured, under vigorous stirring, into a saturated sodium carbonate solution (0.2l), extracted with ethyl ether (3×50 ml). The combined organic extract is washed with a 2% sodium hydrogen carbonate solution. Evaporation of the solvent in vacuo leaves an oil. Crystallization of the residue from methanol gives 2-bromo-1,1-dimethoxy-1-(4'-methoxy-phenyl)-ethane (23.5 g, 0.085 mol; yield 85%) as analytically pure product. m.p. 52°-53°C I.R.: C=O stretching is absent. No band is present in the 2.5-3.2 microns region. N.M.R. (CDCl₃/TMS): 3.20 (s, 6H); 3.60 (s, 2H); 3.79 (s, 3H); 6.78-7.48 (AA'BB', 4H). g) 2-iodo-1,1-dimethoxy-1-(4'-methoxy-phenyl)-ethane (G) A mixture of 2-bromo-1-(4'-methoxy-phenyl)-ethanone (22.9 g, 0.1 mol), potassium iodide (66.4 g, 0.4 mol) and acetone (200 ml) is heated at reflux for 3 h. The reaction mixture is cooled, poured into water (0.25 l) and extracted with ethyl ether (3×100 ml). The combined organic extract is washed with water and dried (Na₂SO₄). Evaporation of the solvent in vacuo leaves a residue which by crystallization from petroleum ether gives 2-iodo-1-(4'-methoxy-phenyl)-ethanone (22 g, 0.094 mol, yield 80%), m.p. 63-65°C. A mixture of 2-iodo-1-(4'-methoxy-phenyl)-ethanone (8.3 g, 0.03 mol), trimethyl orthoformate (10 g, 0.08 mol), methanesulfonic acid (0.146 g, 0.0015 mol) and of methanol (50 ml) is kept at 60°C for 3 h. The solution is poured, under vigorous stirring, into a saturated sodium carbonate solution (0.2 l) and extracted with ethyl ether (3×50 ml). The combined organic extract is washed with a 2% sodium hydrogen carbonate solution. The solvent is evaporated in vacuo; crystallization of the residue from methanol gives 2-iodo-1,1-dimethoxy-1-(4'-methoxy-phenyl)-ethane (7.5 g, 0.023 mol, yield: 77%) as analytically pure product, m.p. 54°-55°C. I.R.: C=O stretching is absent. No band in the 2.5-3.2 microns region. h) 2-bromo-1,1-dimethoxy-1-(4'-methoxy-phenyl)-ethane (H) A solution of 2-bromo-1-(4'-methoxy-phenyl)-ethanone (5 g, 22 mmol), triethyl orthoformate (9 g, 61 mmol), methanesulfonic acid (0.3 g, 3.1 mmol) and ethanol (20 ml) is kept at 40°C for 3 h. The solution is poured, under vigorous stirring, into a saturated sodium carbonate solution (0.2 l) and extracted with ethyl ether (3×50 ml). The combined organic extract is washed with a 2% sodium hydrogen carbonate solution. Evaporation of the solvent in vacuo leaves an oil, which is crystallized from methanol to give 2-bromo-1,1-diethoxy-1-(4'-methoxy-phenyl)-ethane (5 g, 16 mmol, yield: 73%) as analytically pure product. m.p.: 55°-56°C. I.R.: C=O stretching is absent. No band in the 2.5-3.2 microns region. N.M.R.: (CCl₄/TMS): 1.23 (t, 6H, J=7.6Hz); 3.47 (q, 4H, J=7.6Hz); 3.57 (s, 2H); 3.80 (s, 3H); 6.73-7.47 AA'BB', 4H). i) 2-bromomethyl-2-(4'-methoxy-phenyl)-1,3-dioxolane (l) 2-bromo-1-(4'-methoxy-phenyl)-ethanone (20 g, 87 mmol), ethylene glycol (54 g, 870 mmol), para-toluenesulfonic acid hydrate (1.7 g, 8.7 mmol) and benzene (50 ml) are heated and stirred together for 5 h in a flask beneath a Dean-Stark trap. The reaction mixture is added dropwise to a well stirred saturated sodium carbonate solution (0.4 l) and extracted with ethyl ether (3×70 ml). The combined organic extract is washed with a 2% sodium hydrogen carbonate solution, dried (Na₂CO₃) and filtered. The solvent is evaporated under reduced pressure to give 2-bromomethyl-2-(4'-methoxy-phenyl)-1,3-dioxolane (23.5 g, 86 mmol; yield: 99%). Crystallization from methanol gives an analytically pure sample. m.p. 78-79°C. I.R.: C=O stretching is absent. No band in the 2.5-3.2 microns region. N.M.R.: (CDCl₃/TMS): 3.67 (s, 2H); 3.83 (s, 3H); 3.90 (m, 2H): 4.13 (m, 2H); 6.80-7.53 (AA'BB', 4H). l) 2-bromomethyl-2-(4'-methoxy-phenyl)-1,3-dioxane (L) Is prepared according to the procedure of Example 1a. Reagents: 2-bromo-1-(4'-methoxy-phenyl)-ethanone (10 g, 43.6 mmol) 1,3-propanediol (33 g, 434 mmol); Catalyst: p-toluenesulfonic acid hydrate (0.85 g, 4.4 mmol) Solvent: Toluene (25 ml) Reaction time: 8 h Yield: 99% Crystallization from methanol gives an analytically pure sample. m.p.: 80°-81°C. I.R.: C=O stretching is absent. No band is present in the 2.5-3.2 microns region. N.M.R.: (CDCl₃/TMS): 1.20 (m, 2H); 3.40 (s, 2H); 3.86 (s, 3H); 3.88 (m, 4H); 6.86-7.47 (AA'BB', 4H). m) 2-bromomethyl-2-(4'-methoxy-phenyl)-4,5-dimethyl-1,3-dioxolane (N) Is prepared according to the procedure of example 1a. Reagents: 2-bromo-1-(4'-methoxy-phenyl)-ethanone (10 g, 43.6 mmol); (±) 2,3-butanediol (40 g, 444 mmol). Catalyst: para-toluenesulfonic acid hydrate (0.85 g, 4.4 mmol) Solvent: benzene (25 ml) Reaction time: 6 h Yield: 99% (as oil) I.R.: C=O stretching is absent. No band in the 2.5-3.2 microns region. N.M.R.: (CDCl₃/TMS): 1.03 (d, 3H, J=5.6Hz); 1.33 (d, 3H, J=5.6Hz); 3.60 (s, 2H), 3.80 (s, 3H): 3.92 (m, 2H); 6.12-7.22 (AA'BB', 4H). n) 2-(1-bromoethyl)-2-(4'-propionamido-phenyl)-1,3-dioxolane (N) Aluminum chloride (600 g, 4.50 mol) is added in portion to a cold (0-10°C) stirred solution of propionanilide (230 g, 1.54 mol) and of propionyl chloride (297 g, 3.2 mol) in carbon disulphide (600 ml). The reaction mixture is heated at reflux for 24 h. It is poured into a mixture of hydrochloric acid and crushed ice, and extracted with methylene chloride. The organic phase is washed with a 1% sodium hydrogen carbonate solution, with water, dried (Na₂SO₄) and filtered. Evaporation of the solvent under reduced pressure gives 1-(4'-propionamidophenyl)-propan-1-one (165 g, 0.8 mol, yield 52%) m.p. 154-155°C. I.R.: 3320 cm⁻¹ (NH stretching); 1665, 1710 cm⁻¹ C=O stretching). N.M.R.: (CDCl₃/TMS): 1.20 (t, 3H, J=7Hz); 1.25 (t, 3H, J=7Hz); 2.45 (q, 2H, J=7Hz); 2.95 (q, 2H, J=7Hz); 7.50-8.07 (AA'BB', 4H). A solution of bromine (16 g, 0.1 mol) in acetic acid (5 ml) is added in 30 min, at room temperature, to a stirred solution of 1-(4'-propionamidophenyl)-propan-1-one (20.5 g, 0.1 mol) in acetic acid (200 ml). The solution is poured into a 2% sodium sulphite solution and extracted with methylene chloride (2×100 ml). The combined organic extract is washed with water, dried with Na₂SO₄. Evaporation of solvent in vacuo leaves a solid residue. Crystallization from methanol provides 2-bromo-1-(4'-propionamido-phenyl)-propan-1-one (23 g, 0.081 mol, yield 81%) as analytically pure product, m.p. 126°-127°C. I.R.: 1670 cm⁻¹ (C=O stretching), 3390 cm⁻¹ (NH stretching). N.M.R.: (CDCl₃/TMS): 1.23 (t, 3H, J=7Hz); 1.87 (d, 3H, J=7Hz); 2.45 (q, 2H, J=7Hz); 5.30 (q, 1H, J=7Hz); 7.27-8.08 (AA'BB', 4H). The bromoketone (7 g, 25 mmol), above prepared, ethylene glycol (20 g, 322 mmol), para-toluenesulfonic acid hydrate (0.5 g, 2.6 mmol) and toluene (20 ml) are heated at reflux and stirred together for 3 h in a flask beneath a Dean-Stark trap. The reaction mixture is added dropwise to a well stirred saturated sodium carbonate solution and extracted with methylene chloride (2×50 ml). The combined organic solution is washed with a 2% sodium hydrogen carbonate solution, dried (Na₂CO₃), filtered and concentrated in vacuo to give (7.3 g, 22.3 mmol, yield 90%) as oil. I.R.: C=O stretching is absent. N.M.R.: (CDCl₃/TMS): 1.20 (t, 3H, J=7Hz); 1.55 (d, 3H, J=7Hz); 2.35 (q, 2H, J=7Hz); 4.00 (m, 4H); 4.30 (q, 1H, J=7Hz); 7.00-7.67 (m, 4H). o) 2-(1'-bromoethyl)-2-(4'-phthalimido-phenyl)-1,3-dioxolane (O) A mixture of 1-(4'-aminophenyl)-propan-1-one (30 g, 0.2 mol), phthalic anhydride (60 g, 0.4 mol) and of acetic acid (300 ml) is heated at reflux for 2 h. The reaction mixture is cooled to room temperature and the precipitate consisting of 1-(4'-phthalimidophenyl)-propan-1-one (41 g, 0.150 mol, yield 75%) is filtered and dried in vacuo. An analytically pure sample is obtained by crystallization from acetic acid, m.p. 213°-214°C. I.R.: 1660, 1640, 1680 cm⁻¹(C=O stretching) N.M.R.: (CDCl₃/TMS): 1.23 (t, 3H, J=7Hz); 3-04 (q, 2H, J=7Hz); 7.27-8.27 (m, 8H). N,N,N,N-trimethyl-phenylammonium perbromide (37.6 g, 0.1 mol) is added, in portion, at room temperature, to a stirred solution of the ketone (28 g, 0.1 mol) (above prepared) in tetrahydrofurane (700 ml). The reaction mixture is filtered, the insoluble washed with tetrahydrofurane. Evaporation in vacuo of the combined tetrahydrofurane solution leaves 2-bromo-1(4'-phthalimido-phenyl)-propan-1-one (36 g, 0.1 mol, yield: 100%) as solid residue. An analytically pure sample is prepared by crystallization from acetic acid; m.p. 189°-190°C. I.R.: 1650 cm⁻¹ (C=O stretching). N.M.R.: (CDCl₃/TMS): 1.90 (d, 3H, J=7Hz); 5.34 (q, 1H, J=7Hz); 7.35-8.35 (m, 8H). The bromoketone (18 g, 50 mmol), above prepared, ethylene glycol (30 g, 0.48 mol) paratoluenesulfonic acid hydrate (1 g, 5.2 mmol) and toluene (35 ml) are refluxed and stirred together for 5 h in a flask beneath a Dean-Stark trap. The reaction mixture is added dropwise to a well stirred saturated sodium carbonate solution and extracted with methylene chloride. The combined organic solution is washed with a 2% sodium hydrogen carbonate solution, dried (Na₂CO₃), filtered and concentrated in vacuo to give the ketal as oil (17.5 g, 45 mmol, yield 90%). I.R.: C=O stretching is absent. No band in the 2.5-3.2 microns region. N.M.R.: (CDCl₃/TMS): 1.64 (d, 3H, J=7Hz); 3.87 (m, 2H); 4.17 (m, 2H); 4.42 (q, 1H, J=7Hz); 7.20-8.10 (m, 8H). p) 2-(1'-bromoethyl)-2-(2-fluoro-4-diphenylyl)-1,3-dioxolane (P) Bromine (0.56 g, 35 mmol) is added, at room temperature and under vigorous stirring, to a solution of 1-(2-fluoro-4-diphenylyl)-propan-1-one (0.8 g, 35 mmol) (prepared according to Japan Kokai 79.109.952-26 August 1979) in chloroform (50 ml). The reaction mixture is poured, under stirring, into a sodium sulfite saturated solution and extracted with chloroform. The organic extract is washed with water, dried (Na₂SO₄) and filtered. Evaporation of the solvent under reduced pressure gives 2-bromo-1-(2-fluoro-4-diphenylyl)-propan-1-one (1 g, 32.5 mmol, yield 93%). N.M.R.: (CDCl₃/TMS): 1.85 (d, 3H, J=7Hz); 5.20 (q, 1H, J=7Hz); 7.50 (m, 8H). 2-bromo-1-(2-fluoro-4-diphenylyl)-propan-1-one (1 g, 32.5 mmol), ethylene glycol (27 g, 435 mmol) and para-toluenesulfonic acid hydrate (0.06 g, 3.00 mmol) and toluene (25 ml) are heated at reflux and stirred together for 5 h in a flask beneath a Dean-Stark trap. The reaction mixture is added dropwise to a well stirred saturated sodium carbonate solution and extracted with toluene. The organic extract is washed with a 2% sodium hydrogen carbonate solution, dried (K₂CO₃) and filtered. Evaporation of the solvent under reduced pressure gives 2-(1-bromoethyl)-2-(2-fluoro-4-diphenylyl)-1,3-dioxolane (1.06 g, 30.2 mmol, yield 93%). N.M.R.: (Toluene/TMS): 1.60 (d, 3H, J=7Hz); 4.35 (q, 1H, J=7Hz). q) 2-bromo-1,1-dimethoxy-1-(2'-thienyl)-propane (Q) A solution of 2-bromo-1-(2'-thienyl)-propan-1-one (10.9 g, 50 mmol) (prepared according to Doklady Akad. Nausk. S.S.S.R. 138 , 115 (1961)], trimethyl orthoformate (16 g, 150 mmol), methanesulfonic acid (1.4 g, 14.5 mmol) in methanol (60 ml) is kept at 45°C for 22 h. Then it is heated at 60°C for 2 h. The solution is poured, under vigorous stirring, into a saturated sodium carbonate solution (0.2 l) and extracted with ethyl ether (3×70 ml). The combined organic extract is washed with a 2% sodium hydrogen carbonate solution. Evaporation of the solvent under reduced pressure gives 2-bromo-1,1-dimethoxy-1-(2'-thienyl)-propane (9.5 g, 36 mmol, 72%) as oil. I.R.: C=O stretching is absent. No band in the 2.5-3.2 microns region. N.M.R.: (CDCl₃/TMS): 1.60 (d, 3H, J=7Hz); 3.25 (s, 3H); 3.35 (s, 3H); 4.5 (q, 1H, J=7Hz); 7.00-7.50 (m, 3H). r) 2-(1'-bromo-propyl)-2-(4-diphenylyl)-1,3-dioxolane (R) Bromine (159.8 g, 1 mol) is added to a solution of 2-bromo-1-(4-diphenylyl)-butan-1-one (224 g, 1 mol) [prepared in accordance with J. Amer. Chem. Soc., 63 , 1939 (1941)] in chloroform (1000 ml) kept at room temperature, under vigorous stirring. The reaction mixture is poured into a saturated solution of sodium sulfite. The organic layer is washed with water, dried (Na₂SO₄) and filtered. The solvent is evaporated under reduced pressure and the residue is crystallized from methanol to give 2-bromo-1-(4-diphenylyl)-butan-1-one (287 g, 0.95 mol; yield 95%), m.p. 73-74°C. N.M.R.: (CDCl₃/TMS): 1.08 (t, 3H, J=7Hz); 2.13 (m, 2H); 5.11 (t, 1H, J=7Hz); 7.37-8.23 (m, 9H). I.R.: 1680 cm⁻¹ (C=O stretching). The ketal R is prepared according to the procedure of Example 1a. Reagents: 2-bromo-1-(4-diphenylyl)-butan-1-one (5 g, 16.5 mmol); ethylene glycol (25 g, 403 mmol). Catalyst: para-toluenesulfonic acid hydrate (0.32 g, 1.68 mmol) Solvent: Toluene (25 ml) Reaction time: 10 h Yield: 100% I.R.: C=O stretching is absent. No band in the 2.5-3.2 microns region. N.M.R.: (CDCl₃/TMS) 0.97 (t, 3H, J=7Hz); 1.83 (m, 2H); 4.00 (m, 4H); 4.26 (t, 1H, J=7Hz); 7.30-7.82 (m, 9H). In a similar way the following compounds may be prepared: 2-bromo-1-(3'-chloro-4'-cyclohexyl-phenyl)-1,1-dimethoxy-ethane 2-bromomethyl-2-(3'-chloro-4'-cyclohexyl-phenyl)-1,3-dioxolane 2-bromo-1,1-dimethoxy-1-(3'-phenoxy-phenyl)-propane 2-(1'-bromo-ethyl)-2-(3'-phenoxy-phenyl)-1,3-dioxolane 2-bromo-1-(4'-bromo-phenyl)-1,1-dimethoxy-propane 2-(1'-bromo-ethyl)-2-(4'-bromo-phenyl)-1,3-dioxolane 2-(1'-bromo-ethyl)-2-[4-(1-oxo-2-iso-indolinyl)-phenyl]-1,3-dioxolane. Examples Example 1 4'-methoxy-phenylacetic acid Methanesulfonic acid (0.64 ml, 10 mmol) is added dropwise to a stirred mixture of red cuprous oxide (1.44 g, 10 mmol) and of trimethyl orthoformate (2 ml, 18 mmol) in methanol (5 ml) at room temperature. The reaction mixture is stirred at 60° for 45 min. 2-iodo-1,1-dimethoxy-1-(4'-methoxy-phenyl)-ethane (G) (1.61 g, 5 mmol) is added to the reaction mixture cooled to room temperature. The reaction mixture is then heated to 60°C, under nitrogen, for 16 h. 4'-methoxy-phenylacetic acid (0.42 g, 2.5 mmol, yield 50%) is obtained by working up the reaction mixture as described in Preparation Example 2. Example 2 2-bromoethyl-ester of (4'-methoxyphenyl)-acetic acid A mixture of 2-bromomethyl-2-(4'-methoxyphenyl)-1,3-dioxolane (2.74 g, 10 mmol), ZnBr₂ (0.73 g, 3 mmol) and of toluene (10 ml) is heated at reflux, under stirring, for 3 h. The reaction mixture is cooled to room temperature, poured in to 3% hydrochloric acid and extracted with toluene (2×25 ml). The combined organic extract is washed with water, dried (Na₂SO₄) and filtered. Evaporation of the solvent under reduced pressure gives 2-bromoethyl-ester of (4'-methoxy-phenyl)-acetic acid (2.68 g, 9.8 mmol, yield 98%) as oil. I.R.: 1740 cm⁻¹ C=O stretching). N.M.R.: (CCl₄/TMS): 3.47 (t, 2H, J=6Hz); 3.60 (s, 3H); 3.73 (s, 3H); 4.37 (t, 2H, J=6Hz); 6.80-7.30 (AA'BB', 4H). Example 3 3-bromo-propyl ester of (4'-methoxy-phenyl)-acetic acid A mixture of 2-bromomethyl-2-(4'-methoxy-phenyl)-1,3-dioxane (2.87 g, 0.01 mol), ZnBr₂ (1.57 g, 0.007 mol) and toluene (10 ml) is heated at reflux, under stirring, for 2 h. The reaction mixture is cooled to room temperature, poured into 3% hydrochloric acid and extracted with toluene (2×25 ml). The combined organic extract is washed with water, dried (Na₂SO₄) and filtered. Evaporation of the solvent under reduced pressure gives 3-bromo-propyl ester of (4'-methoxy-phenyl)-acetic acid (2.73 g, 0.0095 mol; yield: 95%) as oil. I.R.: 1735 cm⁻¹ (C=O stretching). N.M.R. (CDCl₃/TMS): 2.23 (m, 2H); 3.34 (t, 2H, J=6Hz); 3.51 (s, 2H); 3.71 (s, 3H); 4.17 (t, 2H, J=6Hz); 6.70-7.30 (AA'BB', 4H). In an analogous manner several alpha-halo-ketals have been rearranged in the presence of several catalysts, in several solvents and at different temperatures. The results that have been obtained are summarized in the following table wherein: the alpha-halo-ketals are indicated with the capital letter which follows their chemical name in Example 1; the solvents are indicated as DCE (dichloroethane, MEC (methylene chloride), TOL (toluene), TCE (tetrachloroethane), p-XYL (paraxylene); yields as to the ketal used as starting material are based on the alkanoic acids obtained via hydrolysis of crude esters.

Claims: Process for preparing products having general formula: wherein R is selected from the group comprising an aryl, a substituted aryl, a fused heterocyclic aryl, a heterocyclic, a substituted heterocyclic and a fused aryl-heterocyclic radical; provided, however, that R is not 6-methoxy-2-naphthyl and 5-bromo-6-methoxy-2-naphthyl radical; R''' is selected from the group comprising a hydrogen atom, an alkyl having from 1 to 6 carbon atom, an aryl, a substituted aryl, a fused heterocyclic aryl, an heterocyclic, a substituted heterocyclic, a fused arylheterocyclic radical; Y is selected from the group comprising an alkyl radical having from 1 to 6 carbon atoms, a halo-alkyl radical having from 2 to 6 carbon atoms and a benzyl radical, which comprises the rearrangement of products having general formula: wherein R and R''' have the above mentioned meanings, and R' is selected from the group comprising an alkyl radical having from 1 to 6 carbon atoms and a benzyl radical; R'' is selected from the group comprising an alkyl radical having from 1 to 6 carbon atoms and a benzyl radical; R' and R'', together, are an alkylene radical having from 2 to 6 carbon atoms which, together with the group, forms a heterocylic ring; X is a halogen atom in the presence of a Lewis acid excluding Ag⁺. Process according to claim 1 wherein the rearrangement is carried out in the presence of a catalytic amount of the Lewis acid. Process according to claims 1 or 2, wherein the Lewis acid is selected from the group of organic and inorganic metal salts. Process according to claim 3, wherein the Lewis acid is selected from the organic and inorganic salts of copper, magnesium, calcium, zinc, cadmium, barium, mercury, tin, antimony, bismuth, manganese, iron, cobalt, nickel and palladium. Process according to claims 1 or 2, wherein the Lewis acid is salt of a transition metal having two or more valences. Process according to claim 5, wherein the salt of a transition metal is a halide. Process according to claims 1 or 2, wherein the Lewis acid is CuCl. Products having general formula: wherein R''' is an alkyl radical; R is selected from the group comprising a substituted aryl, a fused heterocyclic-aryl, a substituted heterocyclic and a fused aryl-heterocyclic radical; provided, however, that R is not 6-methoxy-2-naphthyl and 5-bromo-6-methoxy-2-naphthyl radical; X is a halogen atom; R' is selected from the group comprising an alkyl radical having from 1 to 6 carbon atoms and a benzyl radical; R'' is selected from the group comprising an alkyl radical having from 1 to 6 carbon atoms and a benzyl radical; R' and R'', together, are an alkylene radical having from 2 to 6 carbon atoms which, together with the group, forms a heterocylic ring; with the proviso, that R is not 4-alkylthiophenyl of R' and R'' are selected from an alkyl radical and X is a bromine atom. 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)-1,3-dioxolane. 2-(1'-chloro-ethyl)-2-(4'-isobutyl-phenyl)-1,3-dioxolane. 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)-1,3-dioxane. 2-(1'-bromoethyl)-2-(4'-isobutyl-phenyl)-4,5-dimethyl-1,3-dioxolane. 2-bromo-1,1-dimethoxy-1-(4'-isobutyl-phenyl)-propane. 2-(1-bromoethyl)-2-(4'-propionamido-phenyl)-1,3-dioxolane. 2-(1'-bromoethyl)-2-(4'-phthalimido-phenyl)-1,3-dioxolane. 2-(1'-bromoethyl)-2-(2-fluoro-4-diphenylyl)-1,3-dioxolane. 2-bromo-1,1-dimethoxy-1-(2'-thienyl)-propane. 2-(1'-bromo-propyl)-2-(4-diphenylyl)-1,3-dioxolane.

Inventors: BELLI, ALDO, GIORDANO, CLAUDIO, UGGERI, FULVIO, VILLA, GIOVANNI
Applicants: BLASCHIM S.P.A.
Application year: 1981
Main classification: C07C67
IPC codes: C07C51, C07C45, C07D333, C07D209, C07C43, C07C59, C07D317, C07D319, C07C67, C07C69