bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation, structure and properties of halogeno(tetraalkylthiuram monosulfide)copper(I)
Authors: van De Leemput P. J. H. A. M. , Willemse J. , Cras J. A. , Groen L.
Published: September 2010

The preparation and properties of the compounds CuXR4tms (X = Cl, Br, I: R = Me and R2 = Pm; X = SCN: R = Me) are reported. The compound CuI(Pm2tms) from which the crystal structure has been solved crystallizes in the triclinic space group Pl [a = 11.822(3), b = 10.572(3), c = 7.833(3) Å, α = 95.62(3), β = 111.73(3), γ = 68.20(2)°] and contains two formula units per unit cell. The structure was refined to a conventional R value of 0.056 for 3829 independent non‐zero reflections. It consists of dimeric molecules in which copper is approximately tetrahedrally coordinated. The two copper atoms are bridged by one of the sulfur atoms of each thiuram monosulfide.
Synthesis of racemic and chiral codeine and morphineviathe dihydrothebainones. (Chemistry of opium alkaloids, Part XI)
Authors: Lie T. S. , Maat L. , Beyerman H. C.
Published: September 2010

Racemic and chiral 1‐(3,5‐dibenzyloxy‐4‐methoxybenzyl)‐1,2,3,4‐tetrahydro‐6‐methoxyisoquinoline (1, Scheme) were N‐methylated, which gave2a. A Birch reduction converted2a,via2b, into the 1,4‐diene3. Acid‐catalysed cyclization of3gave the morphinan4. Selective removal of the hydroxyl group in position 2,viathe 1‐phenyl‐5‐tetrazolyl ether (5), by hydrogenolysis, yielded (‐)‐dihydrothebainone (6). The conversion of6into (‐)‐codeine and (‐)‐morphine is known. In this way our preceding synthesis is shortened by two steps.
Pyrazolato and related anions. Part VI. Vibrational and electronic spectra of salts of 1,2,4‐triazole and 3‐bromo‐1,2,4‐triazole
Authors: van Houten R. , Vos J. G. , Groeneveld W. L.
Published: September 2010

Salts of 1,2,4‐triazole and 3‐bromo‐1,2,4‐triazole with Cd, Zn, Co, Ni, Cu and Ag are reported. The compounds have been identified and characterized by chemical analyses, vibrational and electronic absorption spectra. Different coordination possibilities are discussed in view of the observed vibrational spectra. For the salts of 1,2,4‐triazole, 1,2‐bidentate or tridentate coordinations are observed. In the salts of 3‐bromo‐1,2,4‐triazole, bidentate and tridentate coordinations are assumed.
Ab initio calculations on thermodynamic and kinetic aspects of the isomerization process of some acyclic unsaturated C5H6 hydrocarbons
Authors: van Den Berg A. B. A. , den Boer D. H. W.
Published: September 2010

Ab initio calculations of the thermodynamic stability order of six acyclic unsaturated hydrocarbons are presented. The results are in reasonable agreement with the experimentally observed order in the equilibrium mixture of isomers resulting from the base‐catalyzed isomerizations. The charge distribution and molecular electrostatic potential of two postulated intermediate carbanions involved in these isomerizations are also calculated in order to explain their initial product ratios which have been observed to differ from the thermodynamical order. These properties fail to reproduce the observed kinetic behaviour. Inclusion of polarization does not improve essentially these results. An estimate of the activation entropy on the basis of the shape of the potentials permits of an interpretation in agreement with the observed reactivity.
Cyclic Organolead Compounds II. Synthesis and characterization of several plumbole derivatives
Authors: van Beelen D. C. , Wolters J. , van der Gen A.
Published: September 2010

The synthesis of several plumbole derivatives is reported. Monocyclic compounds may be prepared by the reaction of organoaihthio compounds with diorganolead dibromides. Spirocyclic compounds may be formed from the reaction of dilithio compounds with lead(II) chloride. The compounds are characterized by 1H NMR and IR spectroscopy.
The synthesis of bis(4‐methyl‐3‐pentenyl)thiophenes
Authors: Janssen Cornelus G. M. , Macco Anton A. , Buck Henk M. , Godefroi Erik F.
Published: September 2010

All possible isomers of title compounds 5a‐8a have been prepared. All the routes presented have involved Wittig olefination of dicarbaldehydes 5c‐8c. Synthetic aspects as regards the relevant intermediates are discussed.
A synthetic approach to 17β‐steroidal ethers derived from hydroxymalonic ester
Authors: Loozen H. J. J. , de Winter M. S.
Published: September 2010

Ethers (1 and 2) derived from dimethyl hydroxymalonate and 3‐methoxy‐1,3,5(10)estratrien‐17β‐ol or 17β‐hydroxy‐4‐androsten‐3‐one have been prepared. The cyclic ethylene acetal of 3‐methoxy‐1,3,5(10)‐estratrien‐17‐one (5) and of 3β‐benzyloxy‐5‐androsten‐17‐one (11) were converted stereoselectively into the corresponding 17β‐(2‐hydroxy‐ethyl) ethers 6 and 12 respectively by LiAlH4/AlCl3. Upon oxidation, esterification and treatment with lithium diisopropylamide/methyl chloroformate the 17‐bis(methoxycarbonyl)methyl esters 1 and 15 were obtained. Catalytic hydrogenolysis of 15, followed by oxidation gave 2.
Functionalized enamines XXVIII. A facile synthesis of 6‐methyl‐19‐norsteroids
Authors: Bieräugel H. , Pandit U. K.
Published: September 2010

Dienamines derived from 8a‐methyl‐1,6‐dioxo‐1,2,3,4,6,7,8,8a‐octahydronaphthalene (2) and ( + )(7aS)‐7a‐methyl‐2,3,5,6,7,8‐hexahydro‐1,5(1H)‐indandione (12) react with 3‐bromo‐2‐(3‐methoxyphenyl)propene (3) to give the corresponding 5‐ and 4‐substituted alkylation products 8 and 14a, respectively. 8 can be directly cyclized to 6‐methyl‐D‐homoequilenin derivative 9 by heating with acid. While 14a can be similarly converted into the corresponding equilenin methyl ether (15a), better yields in the cyclization step are achieved by initial reduction of the 5‐ring ketone function and acetylation of the resulting alcohol. The latter sequence of reactions with 14a, derived from 12, gives optically active 17β‐acetoxy‐6‐methylestra‐1,3,5,7,9,14‐haxaen‐3‐ol methyl ether (15b), which can serve as an central intermediate for optically active steroids.
The Schmidt reaction. Reaction rates of a number of substituted benzoic acids at 20°C
Authors: de Koning Adrianus Jan
Published: September 2010

The rate of the Schmidt reaction at 20°C has been determined for a variety of substituted benzoic acids. It is shown that electronic effects of substituents affect the reaction rate, electron donation increases the rate and electron withdrawal decreases it. Ortho substituents accelerate the reaction, and the reaction is a good example of steric assistance. The buttressing effect of a tert‐butyl group on an adjacent halogen atom is demonstrated in the high reaction rate of 2‐halogeno‐3,5‐di‐tert‐butylbenzoic acids. An attempt has been made to separate the effect of an ortho substituent into steric, inductive and mesomeric contributions. A discussion on the mechanism of the reaction is included.
A simple synthesis of the new heterocyclic compounds 1,4‐oxathiin and 3,5‐dimethyl‐1,4‐oxathiin
Authors: Schoufs Mart , Meijer John , Brandsma Lambert
Published: September 2010

Sulfur dichloride adds to vinylic ethers to give 2,6‐dichloro‐1,4‐oxathianes. Dehydro‐halogenation of these products leads to the hitherto unknown heterocyclic compounds 1,4‐oxathiin 6 and 3,5‐dimethyl‐1,4‐oxathiin 7 in good overall yields.
Chemistry of 2H‐thiopyran and derivatives IV. Deprotonation and methylation of 2H‐thieno[2,3‐b]thiopyran and some derivatives
Authors: Gräfing R. , Brandsma L.
Published: September 2010

Metallation of 2H‐thieno[2,3‐b]thiopyran 1 by strong bases under relatively apolar conditions proceeds exclusively in the 2‐position of the thiophene ring. In polar media a 2‐proton of the thiopyran ring is removed to give the anion 1b. By addition of hexamethylphosphoric triamide (HMPT) to the lithiated compound 1a conversion into 1b takes place. The anions 1a and 1b react with methyl iodide to give the compounds 2 and 3, respectively. Compound 2 can be further methylated by reaction with BuLi in tetrahydrofuran (THF)/HMPT mixtures or sodamide in liquid NH3, followed by addition of methyl iodide. The resulting compound 4 can be converted into the compounds 5, 6 or 7, depending on the base‐solvent system: Compound 5 is produced by interaction between 4 and KNH2 in liquid NH3 at − 33°, followed by methylation at − 60°. If the reaction with KNH2 is carried out at − 60°, however, methylation gives 6, this result is also obtained from 4, BuLi in THF/HMPT and CH3I. Omission of HMPT during the metallation gives rise to vinylic proton abstraction, and subsequent addition of CH3I leads to 7.
Carbophilic reactions of an arylthio‐substituted sulfine with α‐oxo‐carbanions
Authors: van der Leij M. , Zwanenburg B.
Published: September 2010

The reaction of p‐tolyl(phenylthio)sulfine 1 [TolC(SPh)SO, Tol=p‐MeC6H4] with α‐oxo‐carbanions is described. With 2‐lithiocyclohexanone, sulfine 1 furnishes alkene disulfide 2. Similarly, the carbanion of 3,4‐dihydro‐1‐naphthalenone (α‐tetralone) gives disulfide 5. This introduction of a C(Tol)SSPh group into the α‐position of the ketone is explained by assuming an initial carbophilic displacement of the SPh substituent in 1 by the carbanion. Deprotonation of the so‐obtained β‐oxosulfine 3 gives a vinylsulfenate which in a subsequent reaction with thiophenol produces disulfides 2 and 5, respectively. The suggested intermediate vinylsulfenates could be trapped by a reaction with electrophilic reagents. With methyl iodide or benzyl bromide γ‐oxo‐α,β‐unsaturated sulfoxides 6–9 were obtained [introduction of a C(Tol)S(O)R group (R  Me, CH2Ph) in the position α to the carbonyl function of the ketone]. With ethyl bromoacetate or phenacyl bromide the vinylsulfenate obtained from 1 and α‐tetralone does not lead to unsaturated sulfoxides, but to 4,5‐dihydro‐naphtho[1,2‐c]thiophene S‐oxides 15 and 16 instead. These thiophene S‐oxides are thought to arise from an intramolecular condensation of the primary products, i.e. γ‐oxo‐α,β‐unsaturated sulfoxides 21.
Conformational dependence in the photochemistry of (E,E)‐germacra‐1(10),4,7(11)‐triene
Authors: Reijnders Peter J. M. , van Putten Rob G. , de Haan Jan W. , Koning Henk N. , Buck Henk M.
Published: September 2010

Irradiation of (E,E)‐germacra‐1(10),4,7(11)‐triene 1 gives intramolecular reactions of the endocyclic double bonds. Products can be correlated with the crossed and parallel conformation of the title compound and the parallel conformation of its (Z,Z)‐isomer 2.
Chain extension with tert‐butyl lithioacetate
Authors: Bos Wil , Pabon Henk J. J.
Published: September 2010

Iodides containing methylene‐interrupted triple or double bonds can be chain‐extended in 45‐73% yield by reaction with tert‐butyl lithioacetate in THF/HMPT at −35°C and subsequent acid‐catalyzed thermolysis at 100°C. Alkyl and allyl bromides or iodides give acids in yields of 60 to 89%. In some cases, minor amounts of methyl ketones were found. Alkyl chlorides and alkyl methane‐, benzene‐ or p‐toluenesulphonates are not suitable.
Reactions of organolithium‐diazine adducts and dihydrodiazines with electrophilic reagents
Authors: van der Stoel R. E. , van der Plas H. C. , Jongejan H. , Hoeve L.
Published: September 2010

Some organolithium‐diazine adducts and some dihydropyrimidines were treated with electrophilic reagents. Both 4,6‐diphenyl‐1(3)‐lithio‐1,4(3,4)‐dihydropyrimidine and 4,6‐diphenyl‐1,4(3,4)‐dihydropyrimidine were attacked by the electrophilic reagent methyl iodide (methyl chloroformate) at N(3), yielding 4,6‐diphenyl‐3‐methyl(methoxycarbonyl)‐3,4‐dihydropyrimidine. 4,4,6‐Triphenyl‐1,4(3,4)‐dihydropyrimidine upon treatment with methyl iodide gave mainly 3‐methyl‐4,4,6‐triphenyl‐3,4‐dihydropyrimidine. The 3,4‐dihydro structure. of the products was established both spectroscopically and chemically. Reaction of 2‐lithio‐3‐methyl‐2,3‐dihydropyridazine with methyl iodide (methyl chloroformate, tosyl chloride) gave the corresponding 2,3‐dimethyl(2‐methoxycarbonyl‐3‐methyl‐, 2‐tosyl‐3‐methyl)‐2,3‐dihydropyridazine. Reaction of 1‐lithio‐4‐methyl‐ 1,4‐dihydropyridazine with methyl iodide (methyl chloroformate) gave 1,4‐dimethyl(l‐methoxycarbonyl‐4‐methyl)‐1,4‐dihydropyridazine. 1‐Lithio‐2‐phenyl‐1,2‐dihydropyrazine upon treatment with methyl iodide afforded 5‐methyl‐2‐phenylpyrazine. Reaction with carbonyl compounds produced only high‐molecular weight material.
The behaviour of 6‐ and 8‐substituted purines toward potassium amide in liquid ammonia. A new example of tele‐amination
Authors: Kos N. J. , van der Plas H. C. , van Veldhuizen A.
Published: September 2010

Reaction of 6‐chloro‐ and 6‐(methylthio)purine with potassium amide in liquid ammonia leads to the formation of adenine. When these aminations are carried out with 15N‐labelled potassium amide, the 15N label is found to be present in the amino group, proving that these reactions do not involve opening of the pyrimidine ring. Low temperature 1H‐ and 13C‐NMR spectroscopy of solutions of 6‐chloro‐ and 6‐(methylthio)purine in liquid ammonia, containing potassium amide give no evidence for the presence of an intermediary σ‐adduct. 8‐Chloro‐ and 8‐(methylthio)purine undergo a Tschitschibabin amination at position 6 leading to 8‐chloro‐ and 8‐(methylthio)adenine. In addition 8‐chloropurine gives adenine. Evidence is presented that the formation of this product proceeds via a tele‐amination. 6‐tert‐Butyl‐8‐(methylthio)purine and 8‐aminopurine are found to be unreactive towards potassium amide.
Functionalized enamines XXIX. Solvolytic transformations of 2‐methylisoquinolin‐1‐one dichlorocarbene adduct. Synthesis of benzazepinones
Authors: Soetens H. P. , Pandit U. K.
Published: September 2010

Dichlorocarbene, generated from base‐catalysed decomposition of chloroform, adds to the double bond of 2‐methylisoquinolin‐1‐one (1), to give the 1:1 adduct (2). The latter adduct reacts with water to give E‐3‐(formylmethylene)‐2‐methylisoindolinone (3a). Refluxing of 2 in alcohols yields alkoxybenzazepin‐1‐ones. Upon heating (of 2) in dimethoxyethane and subsequent reduction with lithium borohydride, 4‐chloro‐2‐methyl‐1H‐2,3‐dihydro‐2‐benzazepinone (10) was obtained as the main product. Mechanisms for the formation of these products are discussed.
C‐Nitroso compounds. Part XXXIV. Reaction of α‐chloronitroso compounds with methyl and phenyl Grignard reagents. A convenient synthesis of α,α‐dialkyl‐N‐methyl and ‐N‐phenyl nitrones
Authors: Schenk C. , Beekes M. L. , van der Drift J. A. M. , de Boer Th. J.
Published: September 2010

The α‐chloronitroso compounds 1a–1f were made to react with methyl and phenyl Grignard reagents. N‐methyl and N‐phenyl substituted ketonitrones 2 and 3 were obtained in 48‐78% yield. The structure of these labile nitrones is based on their spectroscopic properties and on the formation of characteristic 1,3‐cycloadducts with phenylisocyanate.
Synthesis of fragments of human β‐lipotropin, βh‐LPH. Part IV*. The synthesis of shortened peptides related to des‐1‐tyrosine‐γ‐endorphin [β‐LPH‐(62‐77)]
Authors: Greven H. M. , van Nispen J. W. , Bijl W. A. A. J.
Published: September 2010

The synthesis of several peptides related to β‐LPH‐(62–77) but shortened from the N‐terminal end, is described. In these syntheses use has been made of the classical fragment condensation approach.
The use of Lanthanum‐139 NMR in the study of complexation behaviour of (hydroxy) carboxylate anions
Authors: Vijverberg C. A. M. , Peters J. A. , Kieboom A. P. G. , van Bekkum H.
Published: September 2010

Several La(III)‐(hydroxy) carboxylate complexes in aqueous medium have been studied by means of 139La chemical shift and line‐width measurements.
A new type of base‐induced isomerisation of 1,3‐enynes; the reversal of an enyne system
Authors: Verboom W. , Everhardus R. H. , Zwikker J. W. , Brandsma L.
Published: September 2010

A new type of base‐catalysed isomerisation of conjugated enynes leads to the reversed enyne systems. The preparative conversion of 1‐(dialkylamino)‐3‐buten‐1‐ynes (1) into 1‐(dialkylamino)‐1‐buten‐3‐ynes (2) is presented.
The implementation of constraints in molecular mechanics to explore potential energy surfaces
Authors: van de Graaf B. , Baas J. M. A.
Published: September 2010

The implementation of a Lagrange multiplier method in a molecular mechanics computer program is discussed. This gives a very efficient method to apply constraints in empirical force field calculations for the exploration of potential energy surfaces.
NAD(P)H models XV. Reduction of Δ4‐3‐ketosteroids via their iminium salts, by 1,4‐dihydropyridine derivatives
Authors: Case Ronald A. , Pandit Upendra K.
Published: September 2010

Pyrrolidinium salts derived from a series of 17‐substituted Δ4‐3‐ketosteroids are reduced by 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) and 2,6‐dimethyl‐3,5‐diethoxycarbonyl‐1,4‐dihydropyridine (Hantzsch ester, 1 eq.) to the corresponding isomeric 5α‐ and 5β‐enamines which hydrolyse to the corresponding 3‐ketosteroids. In the case of the Hantzsch ester reduction, proton transfer from the oxidized Hantzsch ester to the enamine results in the formation of iminium salts, which are further reduced to the corresponding ammonium salts. Mechanistic, stereochemical and biochemical implications of the reactions are discussed.
The reactions of hetero‐allenes RN=C=X with phosphine derivatives containing a PH bond
Authors: Thewissen D. H. M. W. , Ambrosius H. P. M. M.
Published: September 2010

Phosphine derivatives containing a PH bond can add to the C=N double bond of a hetero‐allene molecule RN=C=X. Ph2PH gives Ph2PC(X)NHR (X = O, S: R = Ph; X = N‐p‐tol: R = p‐tol), cy‐C6H11PH2 gives cy‐C6H11P[C(X)NHPh]2 (X = O, S) And Ph2P(Q)H gives Ph2P(Q)C(X)NHR (Q = O: X = S and R = Ph; Q = S: X = O,S and R = Ph, X = N‐p‐tol and R = N‐p‐tol).

The preparation of the new compounds, Ph2PC(N‐p‐tol)NH‐p‐tol, Ph2P(S)C(N‐p‐tol)NH‐p‐tol, Ph2P(O)C(O)NPhC(O)NHPh, cy‐C6H11P[C(S)NHPh]2 and cy‐C6H11P[C(O)NHPh]2, is reported.
The use of the 2,4‐dinitrophenyl group in sugar chemistry re‐examined
Authors: Koeners H. J. , de Kok A. J. , Romers C. , van Boom J. H.
Published: September 2010

The use of the tertiary base 1,4‐diazabicyclo[2,2,2]octane, together with 1‐fluoro‐2,4‐dinitrobenzene in the solvent DMF, proved to be an efficient method for the introduction of the 2,4‐dinitrophenyl (DNP) group at different positions, including the anomeric centre of glucose and galactose. The introduction of the DNP ethers at the anomeric centre leads exclusively to the formation of β‐DNP ethers. The latter derivatives can be easily converted with potassium carbonate in DMF into the α‐DNP ethers. The X‐ray analysis of 2,4‐dinitrophenyl‐2,3,4,6‐tetra‐O‐acetyl‐α‐D‐gluco‐pyranoside is discussed. The DNP group can also be used as a protective group in the synthesis of a disaccharide (i.e. 8) and as a UV probe to monitor (254 nm) and analyse (HPLC) sugar intermediates.
Synthesis of 1,6‐bis(2′‐benzimidazolyl)‐2,5‐dithiahexane and its copper compounds
Authors: Birker P. J. M. W. L. , Helder J. , Reedijk J.
Published: September 2010

The new S2N2‐donor ligand 1,6‐bis (2′‐benzimidazolyl)‐2,5‐dithiahexane, [(C6H4NNHC)CH2SCH2‐]2, has been prepared from 3,6‐dithiaoctanedioic acid and ō‐phenylenediamine. Stable copper (I) and copper (II) complexes are formed. The ESR and optical spectra of the copper (II) complexes are consistent with trigonal bipyramidal coordination of the metal ion.
Preparation and photolysis of deuterium‐labelled rhodopsin analogues
Authors: Fransen M. R. , Palings I. , Lugtenburg J. , Jansen P. A. A. , Groenendijk G. W. T.
Published: September 2010

The compounds 18‐ and 19‐trideutero‐11‐cis‐retinal, > 99% pure, with over 98% and 99% trideuterium incorporation were synthesized together with the corresponding all‐trans derivatives. Rhodopsins were prepared from bovine opsin and 18‐ and 19‐trideutero‐11‐cis‐retinal. 18‐ and 19‐trideutero‐all‐trans‐retinal were isolated as oximes after photolysis of the corresponding rhodopsins. The oximes showed the same deuterium incorporation as the starting 18‐ and 19‐trideutero‐11‐cis‐retinals and as those oximes obtained by denaturation of 18‐ and 19‐trideuterorhodopsin in the dark.

These results demonstrate that during rhodopsin photolysis no detectable exchange of D or H occurs at carbon atoms 18 and 19.

These facts, together with Resonance Raman data of 18‐trideutero‐bathorhodopsin and 5‐demethyl‐bathorhodopsin, establish that the primary step in rhodopsin photochemistry is not a phototautomerization involving the 5‐CH3 group. With respect to the possibility that the primary step is a phototautomerization involving the 9‐CH3 group, the situation is less clear.

At this time tile experimental evidence of the various research disciplines is insufficiently conclusive to establish unambiguously which of the two possibilities, cis‐trans photoisomerization or phototautomerization involving the 9‐CH3 group, is the primary event in visual photochemistry.
Etude des spectres de masse des thiocétones aliphatiques acycliques; mécanismes des fragmentations
Authors: Paquer D. , Morin L. , Vazeux M. , Andrieu C. G.
Published: September 2010

An examination of the mass spectra of aliphatic thioketones at 70 eV has shown some differences between these compounds and the corresponding ketones: the molecular ions of the thioketones were stronger than those of the ketones, indicating the greater ability of the sulfur atom to stabilise the radical cation; the loss of •SH was found to be a characteristic fragmentation of aliphatic thioketones.
Equilibrium studies on rare‐earth chelates: Interactions of rare‐earth ions with thioformohydroxamic acid
Authors: Mathur S. P. , Bhandari C. S.
Published: September 2010

The complexation of rare‐earth ions viz. La(III), Pr(III), Nd(III), Sm(III), Gd(III) and Y(III) with thioformohydroxamic acid has been investigated potentiometrically at 30 ± 1°C in a 70 per cent (v/v) dioxane/aqueous medium at 0.1 M ionic strength using the Bjerrum‐Calvin titration technique. Stepwise and overall stability constants of all the complex species formed are reported. The values obtained by other methods such as Least Square, Block and McIntyre, Schroder and pointwise calculation are in reasonable agreement with the Bjerrum‐Calvin half‐integral method. The stability order for 1:1 metal‐ligand chelate is found to be

Sm > Nd > Gd > Pr > La > Y
Synthesis of dehydroamino acids and didehydrodioxopiperazines and their conversion into α‐mercapto‐α‐amino acid derivatives
Authors: Herscheid Jacobus D. M. , Scholten Henk P. H. , Tijhuis Marian W. , Ottenheijm Harry C. J.
Published: September 2010

A synthesis of α,β‐dehydroamino acid derivatives 12 is described, which is of possible general applicability and might be useful for the preparation of peptides which have such a moiety in their sequence. In addition, several didehydrodioxopiperazines (13–17) have been prepared. The reactivity of these compounds towards liquid H2S in the presence of ZnCl2 has been studied. Only the dehydroalanine derivatives 12a and 13 gave α‐addition products; all other dehydroamino acid derivatives and cyclic dipeptides failed to react cleanly.
Allophane and halloysite minerals. Structural considerations
Authors: de Roy G. , Verhaert I. , Vansant E. F.
Published: September 2010

New Zealand allophane and halloysite samples were investigated using sorption, DTA, infrared, crystallographic and Mössbauer techniques. The data support the hypotheses linking both minerals, although marked differences were detected, which are related to their structures and consequently, to their polarity.
2,2′‐Pyrromethene‐5[1H]‐one, its 1‐ and 1′‐mono‐ and 1,1′‐dimethyl homologues; Synthesis, thermal and photochemical reactivity
Authors: Onkenhout W. , van Koeveringe J. A. , Lugtenburg J.
Published: September 2010

2,2′‐Pyrromethene‐5[1H]‐one*, together with the 1‐ and 1′‐monomethyl and 1,1′‐dimethyl homologues are prepared in high yield.

2,2′‐Pyrromethene‐5[1H]‐one (1) and its 1′‐methyl homologue (2) are obtained in the Z form and the 1‐methyl (3) and 1,1′‐dimethyl homologue (4) in the E form. All four systems photoisomerize upon irradiation with light (λ > 360 nm) (Fig. 1). Separation of the photoisomeric mixtures provides the geometrical isomers that cannot be obtained via the thermal synthesis. The photoisomers do not isomerize thermally in refluxing methanol. Upon addition of sodium carbonate in methanol the photoisomers are converted back to the original isomers, demonstrating that Z‐(1), Z‐(2), E‐(3) and E‐(4) are thermodynamically more stable than E‐(1), E‐(2), Z‐(3) and Z‐(4), respectively. The presence of the 1‐methyl group in 2,2′‐pyrromethene‐5[1H]‐one systems is reflected in the thermodynamics and the photochemistry of these molecules.
Some stable substituted cycloheptatrienyl carbanions
Authors: Zwaard A. W. , Kloosterziel H.
Published: September 2010

The reaction of some 7‐substituted cycloheptatrienes with KNH2 in liquid ammonia is described. In several cases stable carbanions are formed. Their NMR spectra are consistent with a non‐planar pentadienyl‐like structure. A comparison of the 1H‐NMR spectra of 10 and 11 shows the paratropic character of the cycloheptatrienyl anions.
Gold clusters containing bidentate phosphine ligands. Preparation and X‐Ray structure investigation of [Au5(dppmH)3(dppm)](NO3)2 and [Au13(dppmH)6](NO3)n
Authors: van der Velden J. W. A. , Vollenbroek F. A. , Bour J. J. , Beurskens P. T. , Smits J. M. M. , Bosnian W. P.
Published: September 2010

The evaporation of metallic gold into an ethanolic solution of bis(diphenylphosphino)‐methane (dppmH) and NH4NO3 results in the formation of [Au5(dppmH)3(dppm)](NO3)2 with (dppm) = [Ph2PCHPPh2]−; an X‐Ray structure analysis revealed the presence of a Au‐C bond. Full physical data, including 197Au‐Mössbauer, are presented. The icosahedral Au13(dppmH)6 cation was prepared by reacting an ethanolic solution of Au2(dppmH)(NO3)2 with NaBH4; an X‐ray study is reported.
Solvent‐Reactant‐Support interactions in liquid phase hydrogenation
Authors: Koopman P. G. J. , Buurmans H. M. A. , Kieboom A. P. G. , van Bekkum H.
Published: September 2010

The effect of mixed solvents and catalyst support on the rate and selectivity of Ru‐catalyzed liquid phase hydrogenations has been studied. Experiments in 1‐propanol/water mixtures with Ru/C showed the adsorption of reactants on the catalyst and the reaction rate to vary with the composition of the solvent system. The influence of the support, in combination with the solvent surrounding the catalytic metal, on the selectivity in the competitive hydrogenation of cyclohexanone and cyclohexene has been studied using hydrophilic and hydrophobic supports in water/hydrocarbon mixtures. The results demonstrate the importance of both solvent‐support interactions and partition of the reactant between bulk solvent and adsorbed solvent.
Conformational energies and geometries of some oxa‐ and dioxabicyclo[3.3.1]nonanes from molecular mechanics
Authors: van Cranenburgh P. E. J. Peters , Peters J. A. , Baas J. M. A. , van de Graaf B. , de Jong G.
Published: September 2010

Empirical force field calculations have been performed on 2‐oxabicyclo[3.3.1]nonane, 3‐oxabicyclo[3.3.1]nonane and on 2,4‐dioxabicyclo[3.3.1]nonane and some of its methyl substituted derivatives. In 2‐oxabicyclo[3.3.1]nonane the cc and bc conformers are about equally strained. The calculations show that for 3‐oxabicyclo[3.3.1]nonane the cc, and for 2,4‐dioxabicyclo[3.3.1]nonane the bc, is the most stable conformation; the cc has a steric strain which is 8.3 kJ mol−1 higher. Replacement of the methylene units of bicyclo[3.3.1]nonane by ether oxygens seems to be mainly reflected in the amount of flattening of the wings in the various conformers. In the cc conformer of 3‐oxabicyclo[3.3.1]nonane the flattening is relatively small, whereas in 2,4‐dioxabicyclo[3.3.1]‐nonane the extent of the flattening is large with respect to the carbocyclic system. The calculated geometries and barriers to methyl rotation for the be conformer of 3,3‐dimethyl‐2,4‐dioxabicyclo‐[3.3.1]nonane and for the cb conformer of the 7,7‐dimethyl derivative show characteristic differences.
The chemistry of small ring compounds. Part 44. Solvolysis of cyclopropyl sulfides and ethers
Authors: Jorritsma R. , Steinberg H. , de Boer Th. J.
Published: September 2010

1‐Chlorocyclopropyl methyl ether and the corresponding sulfide are methanolysed without any rupture of the three‐membered ring. The solvolysis of 1‐halocyclopropyl sulfides has been studied kinetically and takes place via an SN1 mechanism. Methyl substituents in the cyclopropyl ring promote ring opening. This, and the effect of variation of the leaving group (Cl, Br, SMe2⊕), can be rationalised in terms of relative stabilities of intermediary substituted cyclopropyl and alkyl cations.
Chiroptical properties of 2‐alkylaziridines and their N‐methyl derivatives
Authors: Maat L. , Wulkan R. W.
Published: September 2010

Some optically active 2‐alkylaziridines and their N‐methyl derivatives have been prepared from the corresponding L‐amino acids. Both the ORD and the CD spectra of the aziridines have been determined. From these spectra it is concluded that a cis orientation of the lone pair of the nitrogen, relative to the 2‐alkyl substituent, can be correlated with a negative Cotton effect in the 200 nm region.
Rearrangement of 5α‐hydroperoxy‐6‐estren‐17‐one to 6‐oxa‐B‐homo‐4,7‐estradien‐17‐one. Preferred migration of the vinyl group
Authors: Peters J. A. M. , van Vliet N. P. , Zeelen F. J.
Published: September 2010

Criegee rearrangement of 5α‐hydroperoxy‐6‐estren‐17‐one gave 6‐oxa‐B‐homo‐4,7‐estradien‐17‐one. This confirms that, in this rearrangement the alkenyl group has a greater migratory aptitude than the alkyl group.
The mechanism of the photooxidation of 1‐(9‐phenanthryl)‐4‐phenyl‐1‐buten‐3‐yne
Authors: van Arendonk R. J. F. M. , Laarhoven W. H.
Published: September 2010

Irradiation of 1‐(9‐phenanthryl)‐4‐phenylbutenyne (1) in aprotic solvents containing oxygen gives two products, namely a photocyclization product, 1‐phenyltriphenylene 3, as is usually formed from diarylbutenynes, and a photooxidation product (2), derived from cyclopropapyrone. The formation of the latter product is rather specific to the butenyne 1.

Both products arise from singlet‐ excited butenyne, probably via the same cycloallene intermediate 4. Supposedly, this intermediate is converted by triplet oxygen into a 1,2‐dioxetane, having an exocyclic double bond, from which the oxidation product can be formed by ring opening and further rearrangements. The negligible photooxidation of other butenynes is ascribed to the much shorter lifetime of the corresponding cyclic allenes.
4‐Nitrophenyl 4‐morpholinylphosphonochloridate: A convenient reagent for the synthesis of ribonucleoside mono‐, di‐ and tri‐phosphates
Authors: den Hartog J. A. J. , van Boom J. H.
Published: September 2010

The synthesis of the crystalline and easily accessible phosphorylating agent 4‐nitrophenyl 4‐morpholinylphosphonochloridate is reported. Its application to the preparation of 5′‐phosphorylated ribonucleosides (e.g. pA, ppA and pppA) as well as RNA fragments (e.g. pUpU and ppUpU) is demonstrated. Further, special attention is paid to the mild removal of the 4‐nitrophenyl group from fully protected phosphotriester intermediates.
On the relative reactivity of the C  C double bond and the [10] annulene moiety versus SO3
Authors: Lambrechts Hans J. A. , Cerfontain Hans
Published: September 2010

Sulfonation of 11‐methylene‐1,6‐methano[10]annulene (6a) with 1, 3, 4 or 6 equivalents of the dioxane‐SO3 complex in dioxane results in the formation of the 2‐sulfonic acid (6b) as the exclusive 1H NMR detectable product, whereas 1,6‐methano‐[10]annulene (5a) with 3 equiv. of this sulfonating agent already yields the 2,7‐disulfonic acid. The lower reactivity of the peripheral ring of 6a compared with that of 5a is explained in terms of a higher coplanarity of the annulene ring of 6a.
Spectral sensitization of SrTiO3 photoanodes with binuclear 1,10‐phenanthroline bis(2,2′‐bipyridine) complexes of ruthenium(II) and tris‐(2,2′‐bipyridine)ruthenium(II)
Authors: Tinnemans A. H. A. , Mackor A.
Published: September 2010

A single crystal of strontium titanate, used as a photoanode for the photoelectrolysis of water, has been sensitized by mono‐ and binuclear ruthenium(II) complexes in acidic solution for visible light. The dependence of the photocurrent density on light intensity, dye concentration, wavelength and pH has been studied.
Chemical synthesis of thymidine 3′‐diphosphate 5′‐[(phosphonomethyl)phosphonyl phosphate]; an asymmetrically phosphorylated thymidine derivative
Authors: den Hartog J. A. J. , Lawson M. P. , de Jong E. W. P. , van Boom J. H.
Published: September 2010

A suitably protected thymidine 3′,5′‐bis(4‐morpholinylphosphonate) derivative was converted into a derivative with two different 3′‐ and 5′‐phosphoryl functions.
Cannabis XXIII. Synthesis of deuterium‐substituted cannabinoids
Authors: Driessen R. A. , Salemink C. A.
Published: September 2010

On the basis of studies of the relationship between structure and mass‐spectral fragmentation, deuterium‐substituted cannabinoids and analogues thereof have been prepared.
Synthesis and stereochemistry of some 1,2,3,4‐tetrasubstituted pyrrolidines
Authors: Rozing G. P. , de Koning H. , Huisman H. O.
Published: September 2010

Several isomeric 1,2,3‐trisubstituted 4‐hydroxypyrrolidines were obtained from reductions of 1,3‐(diethoxycarbonyl)‐2‐methyl‐4‐oxopyrrolidine and 1,2‐(diethoxycarbonyl)‐3‐methyl‐4‐oxopyrrolidine. The chemistry of these reductions is discussed. The relative configurations of the hydroxypyrrolidines were determined by chemical interconversions and spectroscopic methods, providing 1H NMR and 13C NMR data which are useful in structural assignment of other pyrrolidine derivatives.
Synthesis of six‐ and seven‐membered heterocycles by reaction of 1‐(2‐chloroethylthio)‐1‐alkynes and 1‐(3‐chloropropylthio)‐1‐alkynes with alkali metal sulfide, selenide and telluride
Authors: Sukhai R. S. , de Jong R. , Verkruijsse H. D. , Brandsma L.
Published: September 2010

Reaction of RCCSCH2CH2Cl (1, R = alkyl) compounds with dilithium disulfide (Li2S2) in ethanol gives 3‐alkyl‐5,6‐dihydro‐1,4‐dithiins (2,n= 2, X = S). With the alkali mono‐sulfide, M2S, dehydrochlorination to (vinylthio)alkynes RCCSCHCH2(3) predominates. Interaction between1,n= 2, and M2Se or M2Te (M = Li or Na) in liquid ammonia gives rise to dehydrochlorination as well as to attack on chlorine with intermediate formation of alkynethiolates RCCS−(4); if this reaction is carried out in ammonia‐free ethanol, the desired 5,6‐dihydro‐1,4‐thiaselenins and ‐thiatellurins (2,n= 2, X = Se or Te) are, in some cases, obtained. The chloro sulfides RCCS(CH2)3Cl (1, R = alkyl or phenyl) with alkali metal sulfide, selenide and telluride yield respectively 3‐alkyl‐ or 3‐aryl‐6,7‐dihydro‐5H‐1,4‐dithiepins, the corresponding 6,7‐dihydro‐5H‐1,4‐thiaselenepins and 6,7‐dihydro‐5H‐thiatellurepins (2,n= 3). When R in the starting compounds2is a Me3Si group, the unsubstituted compounds2(n= 3, R = H) are formed.
The coordination chemistry of optically active ligands. Copper(II) and nickel(II) compounds containing (S)‐(+)‐1‐amino‐2‐propanol as a ligand
Authors: Nieuwpoort G. , Reedijk J.
Published: September 2010

Copper(II) and nickel(II) compounds with (S)‐(+)‐1‐amino‐2‐propanol (S‐ap) are described and compared with the corresponding compounds containing racemic 1‐amino‐2‐propanol ((RS)‐ap) previously reported. Both ligands give analogous coordination compounds, except in the case of the chlorides of formula MCl2(ap)2, which are only obtained with (RS)‐ap. Similar differences were found in solution using conductometric titrations. Infrared and ligand field spectra for the racemic and optically active compounds are almost identical. Circular dichroism spectra show that Λ(δδδ) is the most stable configuration for the tris‐chelates. For the bis‐compounds the ligands could be assigned to cis‐ or trans‐positions by comparing the rotational strength of the d‐d transitions. In addition, the different melting points of the isomers are related to their different geometries. The comparison further indicates that in compounds with monodentate coordinating ap ligands steric hindrance is less important in the case of the compounds containing S‐ap.
Chelation of cis‐Pt(NH3)2Cl2 by the deoxynucleotide d(CCGG)
Authors: Marcelis A. T. M. , Canters G. W. , Reedijk J.
Published: September 2010

The main product of the reaction between cis‐Pt(NH3)2Cl2 and the deoxytetranucleotide d(C‐C‐G‐G) was isolated. A 1H NMR study shows that the two guanosine bases are chelating to cis‐Pt(NH3)2 via their N(7) atoms.
Derivatives of m‐di‐tert‐butylbenzene. Part VI. The preparation of miscellaneous halogenated compounds
Authors: de Koning Adrianus Jan
Published: September 2010

The preparation of seven series of dihalogenated and monohalogenated derivatives of m‐di‐tert‐butylbenzene, comprising twenty three new compounds, is described.
Chemistry of crown ethers. XVII. Triphase catalysis by immobilized benzo‐18‐crown‐6
Authors: van Zon A. , de Jong F. , Onwezen Y.
Published: September 2010

Several immobilized benzo‐18‐crown‐6 derivatives have been synthesized and a study has been made of their activities as triphase catalysts in the reaction between 1‐bromooctane in toluene and aqueous potassium cyanide. In each case the reaction rate was proportional to the 1‐bromooctane concentration and to the amount of catalyst and also depended on the potassium cyanide concentration. Under non‐stirred conditions the activity per crown ether moiety was dependent on the degree of functionalization of the supporting polymer, being high for a highly substituted polystyrene/divinylbenzene resin and low for a sparingly substituted one. The beneficial effect of the high loading disappeared completely, however, under stirred conditions. The triphase catalyst can be used both with liquid‐liquid‐solid and with solid‐solid‐liquid systems and can be recovered without significant loss of activity.
Structure analysis of (+)‐1,3,4,14b‐tetrahydro‐2‐methyl‐2H‐dibenzo[b,f]pyrazino[1,2‐d][1,4]oxazepine monohydrobromide, a potential anti‐depressant
Authors: van Rij‐Oskam J. J. , van Egmond A. B. , Feil D. , Zeelen F. J.
Published: September 2010

The crystal structure and absolute configuration of the title compound were determined and compared with those of (+)‐1,2,3,4,10,14b‐hexahydro‐2‐methyldibenzo[c,f]pyrazino[1,2‐a]‐azepine monohydrobromide (mianserin hydrobromide), a related tetracyclic compound.
Stereoselective synthesis of the imidazole alkaloids (+)‐pilocarpine and (+)‐isopilocarpine. (Imidazole chemistry, Part IX)
Authors: Noordam A. , Maat L. , Beyerman H. C.
Published: September 2010

A novel synthesis of (+)‐pilocarpine (10a) is described. L‐Histidine is converted into methyl (R)‐2‐bromo‐3‐(l‐methyl‐5‐imidazolyl)propionate (5) in which the configuration has been inverted. Alkylation of dibenzyl ethylmalonate with 5 yields the imidazole compound 6, again with inversion. Finally, 6 is converted into a mixture of (+)‐pilocarpine (10a) and (+)‐isopilocarpine (10b), the separation of which is well established.
Chemistry of crown ethers XVIII. Isolation and purification of 18‐crown‐6 by selective complexation with non‐ionic compounds
Authors: van Zon A. , de Jong F. , Reinhoudt D. N. , Torny G. J. , Onwezen Y.
Published: September 2010

A number of non‐ionic compounds have been found to form solid complexes with 18‐crown‐6. The highest efficiencies of isolation and the highest selectivities were obtained with nitromethane, dimethyl carbonate and dimethyl oxalate. The usefulness of these compounds was demonstrated in the isolation of >98% pure 18‐crown‐6 from crude reaction mixtures.
Proton acid induced rearrangements of bicyclo[2.2.0]hexene carboxylic acids and esters
Authors: van Rantwijk F. , van der Stoel R. E. , van Bekkum H.
Published: September 2010

Bicyclo[2.2.0]hex‐5‐ene‐2‐endo‐carboxylic acids and their methyl esters give the corresponding γ‐lactones, together with isomerized products, upon treatment with hydrochloric acid in acetic acid. The reaction mechanism is discussed.
Photochemical reactions of quinoid α‐aryl‐substituted γ‐oxo‐α,β‐unsaturated carboxylic esters and amides. Formation of naphthacene and cycloheptatriene derivatives
Authors: Verboom W. , Brants J. J. M. , Bos H. J. T.
Published: September 2010

Irradiation of the quinoid α‐aryl‐substituted γ‐oxo‐α,β‐unsaturated carboxylic esters 7a‐b and amides 10a‐b, derived from 9,10‐phenanthrenequinone, afforded, in addition to the Z/E isomers, the 8‐oxo‐8H‐benzo[f,g]naphthacene‐9‐carboxylic esters (13a‐b) and amides (15a‐b), respectively, by a dehydro‐cyclization of the stilbene system. Starting from the carboxylic ester 7c and amide 10d, with blocked ortho positions, cycloisomerization via an intramolecular (4 + 2)‐cycloaddition, with formation of the cycloheptatriene derivatives 16 and 17, was observed.

Irradiation of the α‐aryl‐substituted γ‐oxo‐α,β‐unsaturated carboxamides 12, derived from 3,5‐ditert‐butyl‐o‐benzoquinone, afforded, in addition to the Z/E isomers, the corresponding cycloheptatriene‐carboxamides 18. Starting from the carboxamide 12b,Φ = 0.074 ± 0.006 for the Z → E isomerization,Φ= 0.039 ± 0.004 for the E → Z isomerization and for the cycloisomerization Φ= 0.0016 ± 0.0006.
Reactions of low‐valent titanium with various functional groups (phenyl derivatives)
Authors: Dams Rudy , Malinowski Marek , Geise Herman J.
Published: September 2010

Titanium slurries, prepared by reduction of titanium chlorides with LiAlH4, are not only effective in couplings of ketones and aldehydes to alkenes, but also in reductive couplings and reductions of other functional groups.
Semi‐empirical calculations concerning the geometry of the cycloheptatrienyl anion
Authors: Zwaard A. W. , Brouwer A. M. , Mulder J. J. C.
Published: September 2010

Semi‐empirical calculations (mostly MINDO/3) have been performed on singlet C7H7−. A preference for planar structures is evident from the calculations. Two different structures (an allylic structure and a pentadienylic structure, respectively) are found as absolute minima on the potential surface. They were found to be second‐order Jahn‐Teller deformations of the highly symmetrical (D7h) structure, the energy lowering on these distortions being about 9 kcal/mole. A first‐order Jahn‐Teller effect was found to be negligible. The related C5H5+ system is considered briefly for comparison.
Synthesis of 1‐alkoxy‐3‐buten‐1‐ynes and some homologues
Authors: van Rijn P. E. , Everhardus R. H. , Brandsma L.
Published: September 2010

1‐Alkoxy‐3‐buten‐1‐ynes and the homologues ROCC‐CHCR′R″ (R′ and R″  H or alkyl, or R′R″  [CH2]5) have been obtained in satisfactory yields from allenic bis‐ethers RO‐CHCCH‐C(R′)(R″)OR and ethyllithium in diethyl ether. With excess ethyllithium, the enynes C2H5‐CC‐CHCR′R″ (R′  alkyl, R″  alkyl or H or R′R″  [CH2]5) were formed.
A MINDO/3 exploration of some (CH)2+8 structures
Authors: Klumpp Gerhard W. , Fleischhauer Jörg , Schleker Wolfgang
Published: September 2010

Within the context of a study aimed at a possible delocalized structure (IVb) of the cubane dication energies, charges and geometries have been calculated for three known and for four unknown types of dications derived from the (CH)82+ family.
Conformational analysis of an RNA triplet in aqueous solution: m62A‐U‐m62A studied by two‐dimensional nuclear magnetic resonance at 500 MHz
Authors: Lankhorst Peter P. , Groeneveld Cornelis M. , Wille Gerry , van Boom Jacques H. , Altona Cornelis , Haasnoot Cornelis A. G.
Published: September 2010

The complete assignment of the 18 ribose proton NMR signals of the trinucleoside diphosphate m62A(1)‐U(2)‐m62A(3) is given. The analysis was carried out by means of spin‐echo‐correlated spectroscopy and two‐dimensional J‐resolved spectroscopy at 500 MHz. Analysis of the chemical shifts and coupling constants demonstrates that the trimer does not form a classical right‐handed helix. Instead, the interior U(2) fragment appears to be “bulged‐out”, concomitant with a next‐nearest‐neighbour interaction between the terminal purine bases. An analogy with the behaviour of the first three residues in the tetramer m62A(1)‐U(2)‐m62A(3)‐U(4) is noted. An analysis of the coupling constants in terms of the N/S equilibrium and population distribution around the torsional degrees of freedom along the sugar‐phosphate backbone is presented.
Synthesis and reactivity of 22,23‐methylene‐2,3,17,18‐tetramethyl‐23‐hydro‐1, 19‐[21H,24H]‐bilindion‐10‐enium trifluoroacetate
Authors: de Groot J. A. , van der Steen R. , Lugtenburg J.
Published: September 2010

The biliverdinium salt 1 has been prepared in high yield and its behaviour towards nucleophiles studied. The reactions have been found to occur selectively on the central carbon atom 10 and to lead to bilirubin systems. In addition, the photoisomerisation of the bilirubin model compound 5, prepared from 1, has been investigated.
Effect of pressure on the (2 + 2) cycloaddition of cyclopropanone diethyl acetal to tetracyanoethylene
Authors: Wiering Petrus G. , Steinberg Herbert
Published: September 2010

The pressure dependence of the (2 + 2) cycloaddition of cyclopropanone diethyl acetal to tetracyanoethylene in methylene chloride and acetonitrile has been studied. The reaction is about ten times faster in the less polar methylene chloride in the pressure range 1‐2000 atm. The volume of activation is found to be ‐20.9 cm3/mole (CH2Cl2) and ‐24.5 cm3/mole (CH3CN). The estimated volume of the transition state is equal in both solvents and is of the same order of magnitude as the partial molar volume of the cycloadduct 1,1‐diethoxy‐2,2,3,3‐tetracyanocyclopentane. These findings are in agreement with a concerted cycloaddition mechanism via a weak complex of the reactants.
Photochemical, transformations of tetracyclo [3. 3.0.02,4.03,6]OCT‐7‐ene
Authors: Stapersma J. , Klumpp G. W.
Published: September 2010

Cyclooctatetraene is a common product of photolysis of the title compound la. Depending on reaction conditions it is accompanied by benzene (solvent: cyclohexane, γ = 253.7 nm), benzene plus semibullvalene (acetone, 300 nm), and an oxetane (cyclohexane, 350 nm, presence of an equimolar amount of benzophenone).
An approach to the synthesis of [2]benzopyrano[3,4‐c]pyrroles; alternative dopaminergic molecules
Authors: Loozen H. J. J. , Brands F. T. L. , de Winter M. S.
Published: September 2010

Benzyloxy‐substituted [2]benzopyrano[3,4‐c]pyrroles have been prepared by thermolysis of suitably substituted benzocyclobutenes, via an intramolecular Diels‐Alder reaction of the quinodimethane intermediate with an aldehyde function.

Upon thermolysis of 3,4‐bis(benzyloxy)‐7‐[[(methoxycarbonyl)(2‐oxoethyl) amino]methyl]bicyclo‐[4.2.0]octa‐l,3,5‐triene (12), in refluxing bromobenzene,tras‐7,8‐bis(benzyloxy)‐2‐(methoxy‐carbonyl)‐l,2,3,3a,5,9b‐hexahydro[2]benzopyrano[3,4‐c]pyrrole (13) was isolated. Upon thermolysis of N‐alkyl‐N‐(2‐oxoethyl)bicyclo[4.2.0]octa‐l,3,5‐triene‐7‐carboxamides (such as 19, 29a‐d and 33a,b) in bromobenzene,trans/cismixtures of N‐substituted‐3,3a,5,9b,tetrahydro‐2H‐[2]‐benzopyrano‐[3,4‐c]pyrrol‐1‐ones were obtained in yields of 70 to 85%. In this way, 20, 21, 30a‐d, 31a‐d, 34a,b and 35a,b have been obtained. As starting materials, suitably substituted benzocyclo‐butenecarboxylic acids were used (7, 46 and 54). These compounds were converted into the acid chlorides and condensed with substituted 2‐(hydroxyethyl)amines to afford the N‐alkyl‐N‐(2‐hydroxyethyl)benzobicyclo[4.2.0]octa‐l,3,5‐triene‐7‐carboxamides 27, 28a‐d and 32a,b, which were then oxidized to the required N‐(2‐oxoethyl) derivatives by means of DMSO‐oxalyl chloride complex.

Reduction of the tetrahydro‐2H‐[2]benzopyrano[3,4‐c]pyrrol‐1‐ones 20, 21, 30b, 30c and 35b with borane‐dimethyl sulfide complex or with LiAlH4‐AlCl3complex gave the hexahydro[2]benzo‐pyrano[3,4‐c]pyrroles 22, 23, 36, 37 and 38. Subsequently, these compounds were converted into catecholamines 24, 25, 39, 40 and 41 by catalytic reduction.