bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereospecific reactions of the bicyclo[5.4.1]dodecapentaenyl cation
Authors: Brounts Ronald H. A. M. , Buck Hendrik M. 
Published: September 2010

AbstractQuenching of the bicyclo[5.4.1]dodecapentaenyl cation 1 with LiOMe/MeOH afforded endo‐4‐methoxy‐syn‐bicyclo[5.4.1]dodeca‐2,5,7,9,11‐pentaene with the methoxy group in a highly crowded position. The remarkable reactivity of cation 1 can be explained by the intermediacy of a syn transition state having a homocyclopropenyl‐type cation at the exo face of the carbon skeleton. Quenching of 1 with the more bulky acetate anion gave the thermodynamically favoured exo‐4‐acetate derivative.
On the synthesis of 1,n‐diketones using mono‐substituted derivatives of tosylmethyl isocyanide
Authors: van Leusen Albert M. , Oosterwijk Roelof , van Echten Erik , van Leusen Daan 
Published: September 2010

AbstractA new method is described for the synthesis of symmetrical and unsymmetrical diketones. Particularly good results are obtained in the synthesis of 1,6‐ and 1,5‐diketones. Procedures are reported for 1,2‐diketones. The moderate results obtained for 1,4‐diketones and the lack of success for 1,3‐diketones are discussed.
Mild procedures for the synthesis of 1,6‐anhydroaldohexopyranoses
Authors: Kloosterman M. , Dees M. J. , van der Marel G. A. , van Boom J. H. 
Published: September 2010

AbstractPenta‐O‐acetyl‐β‐D‐galactopyranose was converted in two steps into pentabromophenyl 1,2,3,4‐tetra‐O‐acetyl‐β‐D‐galactopyranoside. Short treatment of the latter with tetra‐n‐butylammonium hydroxide at 20°C, followed by acetylation, afforded crystalline 2,3,4‐tri‐O‐acetyl‐1,6‐anhydro‐β‐D‐galactopyranose. The same procedure could also be applied to the synthesis of the per‐O‐acetates of 1,6‐anhydro‐β‐cellobiose and 1,6‐anhydro‐β‐D‐glucopyranose. 2,3,4‐Tri‐O‐acetyl‐1,6‐anhydro‐β‐D‐glucopyranose could also be obtained in a one‐flask procedure by selective tosylation of D‐glucose at the primary hydroxyl group, followed by treatment with base and subsequent acetylation.
The meta‐photocycloadditions of 3‐ and 4‐cyanoanisole to cyclopentene
Authors: Osselton E. M. , Lempers E. L. M. , Cornelisse J. 
Published: September 2010

AbstractThe results of the meta‐photocycloaddition of cyanoanisoles to cyclopentene are in agreement with a mechanism involving a dipolar species. The adducts undergo thermal and photochemical rearrangements.
Reaction of NADH models with methylene blue
Authors: Engbersen J. F. J. , Koudijs A. , van der Plas H. C. 
Published: September 2010

AbstractThe NADH models, (1R)‐1,4‐dihydronicotinamide and (1R)‐1,4‐dihydroquinoline‐3‐carboxamide (1‐4, R = X‐benzyl or octyl), are readily oxidized by methylene blue (MB⊕), yielding the corresponding pyridinium ions and leuco‐methylene blue (MBH). Under aerobic reaction conditions, molecular oxygen, present in the reaction solution, rapidly reoxidizes MBH to MB⊕, thereby allowing the study of the oxidation of the NADH models under pseudo‐first‐order reaction conditions. In order to elucidate the mechanism of the oxidation of the NADH models by MB⊕, the influence of the MB⊕ concentration, solvent and temperature has been studied as well as the effect of substituent variation in the benzyl group in a series of 1‐(X‐benzyl)‐1,4‐dihydronicotinamides (1a‐f). For one of the model compounds, 1‐benzyl‐1,4‐dihydronicotinamide (1a, BNAH), the primary and the secondary isotope effect and the temperature dependence of the kinetic isotope effect have been determined. It is concluded that oxidation of the NADH models by MB⊕ most likely proceeds by a rate‐determining hydride transfer process via a linear, symmetrical transition‐state structure.
The reactivity of azepinyl anions, derived from 2‐(diethylamino)‐5‐phenyl‐3H‐azepines, towards alkylating agents
Authors: Streef J. W. , van der Plas H. C. , Nieman N. , Stam C. H. 
Published: September 2010

AbstractTreatment of 2‐(diethylamino)‐3‐(methylthio)‐5‐phenyl‐3H‐azepine (3b, R = SMe) with potassium amide in liquid ammonia, followed by reaction of the anion formed with methyl iodide, gave 2‐(diethylamino)‐5‐methyl‐3‐(methylthio)‐5‐phenyl‐5H‐azepine (5a), the structure of which was confirmed by X‐ray analysis. Substitution at position 5 (as well as at C‐3) was also observed on reacting the anion of 2‐(diethylamino)‐5‐phenyl‐3H‐azepine, obtained by deprotonation of its conjugate acid with lithium diisopropylamide in N,N,N′,N′‐tetramethyl‐1,2‐ethanediamine, with different alkyl halides.
Acid‐catalyzed hydrolysis of benzenesulfonamides. Rate enhancements by ortho‐alkyl substituents
Authors: Wagenaar Anno , Kirby Anthony J. , Engberts Jan B. F. N. 
Published: September 2010

AbstractPseudo‐first‐order rate constants have been measured for the acid‐catalyzed hydrolysis of a series of N,N‐dimethyl‐ and N‐methyl‐N‐phenylbenzenesulfonamides in 70% (v/v) CF3CO2H/H2O at 99°C. Analysis of the effect of alkyl substituents in the benzene ring shows a remarkable rate enhancement by ortho‐alkyl groups, in contrast with a rate retardation of similar substituents in the corresponding benzamides. The rate enhancement in the sulfonamides is attributed to relief of initial‐state strain in the transition state for hydrolysis. When the sulfonamide moiety is contained in a five‐membered ring fused to a phenyl ring, the rate of hydrolysis is markedly reduced by an ortho‐methyl substituent.
Diels‐alder reaction of thebaine via N‐formylnorthebaine with nitroethene; reduction of the nitro group in 7α‐nitroethenoisomorphinans (chemistry of opium alkaloids, part XX)
Authors: Maat L. , Peters J. A. , Prazeres M. A. 
Published: September 2010

AbstractThebaine (1) was converted into N‐formylnorthebaine (4) via N‐demethylation using diethyl azodicarboxylate followed by treatment with ethyl formate. Diels‐Alder reaction of 4 with nitroethene yielded 5 exclusively with the 6α,14α‐etheno bridge and the nitro group in the 7α‐position. Hydrolysis of 5 and methylation then gave 7, the nitroethene addition product of thebaine. Reduction of 5 and 7 with aluminium amalgam gave the corresponding 7α‐amines 11 and 8, respectively. Reduction of 7 with formamidinesulfinic acid or with lithium aluminium hydride gave only the oxime 9.
The co‐oxidation reaction of isoprene and some aromatic thiols
Authors: van der Laan R. , Moolenaar M. J. , de Koning H. , Huisman H. O. 
Published: September 2010

AbstractThe co‐oxidation reaction between isoprene, some aromatic thiols and molecular oxygen is described. The product distribution, in relation to the nature of the aromatic thiol used, is examined. Steric and electronic factors are discussed.
Isomerization of 4,6‐O‐alkylidene‐1,2‐O‐carbonyl‐α‐D‐galactopyranoses into the corresponding 3,4‐acetals
Authors: Hoogerhout P. , Kloosterman M. , van Boom J. H. 
Published: September 2010

Abstract1,2‐O‐Carbonyl‐4,6‐O‐ethylidene‐ (4), 4,6‐O‐benzylidene‐1,2‐O‐carbonyl‐ (6) and 1,2‐O‐carbonyl‐4,6‐O‐(p‐methoxybenzylidene)‐α‐D‐galactopyranose (7) were prepared from the corresponding 4,6‐O‐alkylidene‐D‐galactopyranoses (1, 2 and 3) by reaction with 1,1′‐carbonyldiimidazole and the isomerization of 4, 6 and 7 into the 3,4‐acetals 8, 10 and 11 (endo/exo mixtures) by various (Lewis) acids studied.
Vitamin‐C‐ and isovitamin‐C‐derived chemistry. Part I. Synthesis of 2,3‐dideoxy derivatives of the Ascorbic acids
Authors: Vekemans Jozef A. J. M. , Boerekamp Jack , Godefroi Erik F. , Chittenden Gordon J. F. 
Published: September 2010

Abstract5,6‐O‐Isopropylidene‐L‐gulono‐ and ‐D‐mannono‐1,4‐lactones are converted into 2‐(dimethylamino)‐1,3‐dioxolane derivatives on treatment with N,N‐dimethylformamide dimethyl acetal in chloroform with azeotropic removal of the methanol thus formed. Quaternisation of the products with iodomethane, followed by thermal decomposition yields the corresponding C(4)‐substituted enantiomeric butenolides. Some aspects of the reactions, the characterisation of the products, and further transformations are described.
Solvent‐Reactant‐Support interactions in liquid‐phase hydrogenation II. Supported metal catalysts modified by a liquid film
Authors: Wismeijer A. A. , Kieboom A. P. G. , van Bekkum H. 
Published: September 2010

AbstractThe effect of impregnating metal on carbon catalysts with liquid films, immiscible with the bulk solvent, on rate and selectivity in liquid‐phase hydrogenations has been investigated. Both acid and alkaline films have been used with benzene and phenol as the reactant. The bifunctional character of such catalysts has been demonstrated and a substantial improvement in selectivity for the hydrogenation of phenol to cyclohexanone has been achieved. The factors contributing to the observed phenomena in such multiphase catalytic reactions are discussed.
Synthesis of 4‐O‐(3,4,6‐tri‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐β‐D‐glucopyranosyl)‐1,6‐anhydro‐3‐O‐(4‐methoxybenzoyl)‐β‐ D‐mannopyranose: A versatile intermediate for the preparation of N,N‐diacetylchitobiose derivatives
Authors: Kloosterman M. , Westerduin P. , van Boom J. H. 
Published: September 2010

Abstract4‐O‐Acetyl‐1,6‐anhydro‐3‐O‐(4‐methoxybenzoyl)‐β‐D ‐mannopyranose was converted in two steps into 4‐O‐acetyl‐1,6‐anhydro‐2‐deoxy‐2‐phthalimido‐β‐D‐glucopyranose. Trimethylsilyl tri‐fluoromethanesulphonate‐catalysed coupling of 1,6‐anhydro‐2,3‐O‐(4‐methoxybenzylidene)‐β‐D‐mannopyranose with 1,3,4,6‐tetra‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐β‐D‐glucopyranose, followed by treatment with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone, afforded the title compound. After triflation, the disaccharide thus obtained was treated with lithium azide or potassium phthalimide to afford 4‐O‐(3,4,6‐tri‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐β‐D‐ glucopyranosyl)‐1,6‐anhydro‐2‐azido‐3‐O‐(4‐methoxy‐benzoyl)‐2‐deoxy ‐β‐D‐glucopyranose and 4‐O‐(3,4,6‐tri‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐β‐D ‐glucopyranosyl) −1,6‐anhydro‐2‐deoxy‐3‐O‐(4‐methoxybenzoyl)‐2‐phthalimido‐β‐ D‐glucopyranose, respectively.
Substituent effects on the meta photocycloaddition of arenes to alkenes
Authors: Osselton E. M. , Lempers E. L. M. , Eyken C. P. , Cornelisse J. 
Published: September 2010

AbstractThe meta photocycloaddition of cyano‐ and (trifluoromethyl)‐substituted anisoles to cyclopentene has been investigated and the product ratios are shown to be compatible with a polar mechanism. The photochemical and thermal interconversions of the major adducts from 3‐cyanoanisole and cyclopentene have also been investigated.
Alkaline degradation of monosaccharides III. Influence of reaction parameters upon the final product composition
Authors: de Bruijn J. M. , Kieboom A. P. G. , van Bekkum H. 
Published: September 2010

AbstractA systematic investigation of the alkaline degradation of monosaccharides is presented. The influence of several parameters upon the degradation reaction has been determined by analysis of the reaction products using HPLC and, in some cases, GC. The HO− and the monosaccharide concentrations markedly influence the final product composition with respect to both the amount of C1 to C6 acids and the formation of oligomeric acidic products, the so‐called > C6 acids. Maximum yields of these > C6 acids, up to 50 mol‐C6‐%, are obtained at an HO− concentration of between 10−3 M and 10−2 M when the monosaccharide concentration exceeds 10−2 M. The presence of divalent calcium increases the retro‐aldolization of monosaccharides in alkaline medium, as illustrated by the enhanced production of lactic acid, by complexation with, for instance, d‐fructose. Borate partly protects monosaccharides against alkaline degradation through their borate esters, whilst the amount of saccharinic acids in the degradation product mixture is doubled. On the other hand, neither chloride and carbonate nor the reaction temperature influences the final product composition. Alkaline degradation experiments with pyruvaldehyde, glyceraldehyde and 1,3‐dihydroxyacetone, all assumed to be reaction intermediates, indicate that aldolization of (di)carbonyl compounds causes the formation of substantial amounts of > C6 acids.
1,3‐Halogen shift of 2‐halogeno‐4,5‐dimethylphenols following oxidation with Fremy's salt
Authors: Jacobs A. W. C. M. , Maat L. 
Published: September 2010

AbstractOxidation of 2‐bromo‐6‐deuterio‐4,5‐dimethylphenol with Fremy's salt, followed by in situ reduction, yielded mainly 3‐bromo‐4,5‐dimethylpyrocatechol**, which affords evidence for a 1,3‐bromine shift during the oxidation. The same treatment of 2‐chloro‐4,5‐dimethylphenol yielded 4,5‐dimethylpyrocatechol with a minor amount of 3‐chloro‐4,5‐dimethylpyrocatechol. The 2‐iodo compound gave 4,5‐dimethylpyrocatechol as the only reaction product
2,4‐O‐benzylidene‐D‐ribono‐1,5‐lactone: A revision of structure
Authors: Chittenden Gordon J. F. , Regeling Henk 
Published: September 2010

AbstractThe main product resulting from the reaction of d‐ribonolactone with benzaldehyde dimethyl acetal is a 2,3‐O‐benzylidene derivative of the 1,4‐lactone, and not the 2,4‐O‐benzylidene analogue of the 1,5‐lactone, as suggested previously. Chemical and physical evidence supports the re‐assigned structure.
II. Thermal nitration of olefins with tetranitromethane. Evidence for homolytic initiation of a chain mechanism
Authors: Masnovi J. M. , Kochi J. K. 
Published: September 2010

AbstractTetranitromethane (TNM) reacts spontaneously with N‐vinylcarbazole to afford the product of 1,2‐addition. Under the same conditions, 9‐vinylanthracene and other olefins do not react with TNM until they are deliberately stimulated by a short pulse of visible light. Photo‐activation under these conditions is associated with the charge‐transfer excitation of the olefin‐TNM complex to produce NO2. The subsequent homolytic addition of NO2 to the olefinic donor, followed by electron transfer of the radical adduct, is responsible for the novel chain mechanism for TNM addition in Scheme 1. Homolytic initiation can also be achieved chemically with various additives such as the electron‐rich ferrocene, N,N,N′,N′‐tetramethyl‐1,4‐phenylenediamine, and 5H‐dibenz[b,f]azepine which generate NO2 by dissociative electron attachment to TNM. The limited quanta of light and traces of chemical initiators indicate that the chain mechanism for the addition of TNM occurs with relatively long kinetic chain lengths. The mechanistic implications of the chain mechanism for the formation of various types of products is discussed in the context of olefin structures.
Ene reactions with α‐chloronitroso compounds: Asymmetric synthesis of N‐allylhydroxylamines
Authors: Kreße G. , Felber H. , Ritter A. , Ascherl B. , Vasella A. 
Published: September 2010

AbstractThe α‐chloronitroso mannose derivative 1 undergoes ene reactions with alkenes 2 to yield nitrone hydrochlorides 3 which may be hydrolyzed to allylic hydroxylamines. The enophilic reactivity of 1 is much higher than that of other α‐chloronitroso compounds. The reaction seems to be highly diastereoselective.
Synthesis and silver‐ion‐catalyzed reactions of 3,3′‐ethylenebicyclopropenyl
Authors: Peelen F. C. , Landheer I. J. , de Wolf W. H. , Bickelhaupt F. 
Published: September 2010

AbstractThe title compound 2 was obtained from 1,2‐dimethylenecyclobutane (1) by double addition of dibromocarbene to give the tetrabromide 9, followed by tin hydride reduction to the dibromide 10 and potassium tert‐butoxide elimination of HBr to furnish 2. Silver‐ion‐catalyzed reaction of 2 did not furnish the expected 1,2‐ or 1,4‐ethylene Dewar benzenes 3 and 4, respectively. Instead, in CDCl3 or dioxane, polymeric material was obtained, while in methanol or methanol‐O‐d1, opening of one or both cyclopropene rings and addition of methanol gave 11 or 12E/Z, respectively, depending upon the reaction conditions. The two latter compounds provide valuable information about intermediate 13 in the silver‐ion‐catalyzed rearrangement of bicyclopropenyls to Dewar benzenes. The mechanism of this reaction is discussed.
A double singlet oxygen oxidation in the formation of α, β‐unsaturated lactones
Authors: Wasserman Harry H. , Lu Ta‐Jung 
Published: September 2010

AbstractSystems containing both oxazole and selenide units may be constructed so as to yield α,β ‐unsaturated triamides in one step on dye‐sensitized photooxidation. These products may serve as precursors of α,β ‐unsaturated lactones
Cyclopropanation of olefins by ethyl diazoacetate: Copper‐ and copper‐complex‐containing X‐zeolites as the catalysts
Authors: Oudejans J. C. , Kock‐Van Dalen A. C. , van Bekkum H. , Kaminska J. 
Published: September 2010

AbstractCyclopropanation of olefins by ethyl diazoacetate has been carried out making use of the catalytic action of Cu‐loaded X‐type zeolites upon the decomposition of ethyl diazoacetate. The activity of the NaCuX zeolites is linearly dependent upon the Na‐exchange level. Compared to conventional copper catalysts, the zeolite catalysts give rise to relatively low amounts of polymeric side‐product which is assumed to be formed at the outer zeolite surface. The stereoselectivity obtained with the zeolite catalysts does not deviate significantly from that obtained using copper salts. Zeolite X, loaded with chiral copper complexes, gives rise to only minor asymmetric induction upon cyclopropanation of 1,1‐dichloro‐4‐methyl‐1,3‐pentadiene with ethyl diazoacetate.
Synthesis and properties of peripherally substituted phthalocyaninatocobalt complexes with bisaxially coordinated ligands
Authors: Hanack Michael , Fay Reinhold 
Published: September 2010

AbstractThe synthesis and characterization of peripherally substituted phthalocyaninatocobalt compounds, RmPcCoCl2 and Na[RmPcCo(CN)2] with R = CH3, OCH3, Cl, m = 8; R = t‐Bu, NO2, m = 4, are reported. The latter can be obtained via two methods: either by treatment of RmPcCoCl2 with sodium cyanide or by the reaction of RmPcCo with sodium cyanide in the presence of oxygen. Starting from Na[RmPcCo(CN)2], with R = CH3, m = 8 and R = NO2, m = 4, the corresponding cyano‐bridged polymers, [RmPcCoCN]n, were obtained. The IR, FIR, UV/VIS, 1H NMR (in part) and TG/DTA data are discussed in detail for all the compounds prepared. [(CH3)8PcCoCN]n showed a powder conductivity of σRT 5 · 10−5 S/cm (E 0.22 eV), whereas [(NO2)4PcC(CN)]n has a much lower value, σRT 3 · 10−9 S/cm.
The crystal and molecular structure of aminocyclopropane
Authors: de Boer J. S. A. M. , Schenk H. , Stam C. H. 
Published: September 2010

AbstractC3H5NH2 has a rhombohedral space group R3c, a = 18.784(2), c = 5.494(2) Å (170.5 K), Z = 18. The final R for 1028 reflexions is 0.035. The molecule has an s‐trans pyramidal conformation and the ring bond lengths, after correction for thermal motion, are; vicinal 1.500(3) and 1.497(3), distal 1.506(3) Å. C‐N 1.457(2) Å.
Alkaline degradation of monosaccharides V: Kinetics of the alkaline isomerization and degradation of monosaccharides
Authors: de Bruijn J. M. , Kieboom A. P. G. , van Bekkum H. 
Published: September 2010

AbstractA new kinetic model for the alkaline isomerization and degradation of monosaccharides is presented which includes the interconversion of D‐glucose, D‐fructose, D‐mannose and D‐psicose. Computer simulations using this model fit the experimental data and allow the determination of all relevant reaction rate constants. Additionally, it has been established that, for the alkaline degradation of either D‐fructose, D‐glucose or D‐mannose, substantial amounts of acidic products, i.e. ∼65% and ∼20%, are formed via D‐fructose and D‐psicose, respectively.The influence of some reaction parameters on the pseudo‐first‐order rate constants involved in the kinetic model has been investigated. The enolization of monosaccharides appears to be the rate‐limiting step in both the isomerization and the degradation reactions. The enolization rate is markedly enhanced at higher HO− concentration or by the addition of calcium(II). Direct retro‐aldolization of D‐fructose and D‐psicose occurs at [HO−] > 10−2 M or in the presence of calcium(II), leading to an additional increase in the degradation rate towards lactic acid. The shift of the isomerization equilibrium by borate towards D‐fructose and D‐psicose is accompanied by a decrease of the degradation rate constants, due to stabilization of the monosaccharides as their borate esters.
Spectroscopic characterization of 1‐methylene‐2‐vinylcyclopropane and some of its derivatives
Authors: Brouwer A. M. , Jacobs H. J. C. 
Published: September 2010

AbstractThe characteristic NMR and vibrational spectroscopic properties of 1‐methylene‐2‐vinylcyclopropane 1 and some of its derivatives are described and discussed. The exocyclic CC stretching vibration is consistently found at 1745 cm−1. The 1H NMR spectra show coupling patterns among the methylene and ring protons that are essentially independent of the substituents. The coupling constant between H‐2 and the α‐proton of the substituent depends on the conformation. 13C chemical shifts and coupling constants are readily interpreted using common substituent effect rules. MNDO calculations provide proton‐proton distances and bond orders which are used to interpret proton relaxation rates and proton‐proton coupling constants.
TheDiels‐Alderreaction with 6‐methylene‐7‐octenoic acid, a functionalised butadiene
Authors: Cardinale G. , Laan J. A. M. , Ward J. P. 
Published: September 2010

AbstractA novel functionalised butadiene, 6‐methylene‐7‐octenoic acid, was synthesized from myrcene (7‐methyl‐3‐methylene‐1,6‐octadiene).Diels‐Alderadducts were formed with maleic anhydride and cyclopentene‐3,5‐dione.
A general procedure to convert H‐phosphonate mono‐ or diesters of nucleic acids into valuable phosphate di‐ or triesters
Authors: de Vroom E. , Spierenburg M. L. , Dreef C. E. , van der Marel G. A. , van Boom J. H. 
Published: September 2010

AbstractTreatment of properly‐protected d‐nucleoside 3′‐H‐phosphonate mono‐ or diesters with N,O‐bis(trimethylsilyl)acetamide, followed by the addition of an appropriate chloride, affords 3′‐phosphate di‐ or triester derivatives, respectively.
(2‐Cyano‐1,1‐dimethylethoxy)bis(diethylamino)phosphine: A convenient reagent for the synthesis of DNA fragments
Authors: Marugg J. E. , Burik A. , van der Marel G. A. , van Boom J. H. , Nielsen J. , Dahl O. 
Published: September 2010

AbstractThe phosphitylating reagent (2‐cyano‐1,1‐dimethylethoxy)bis(diethylamino)phosphine proved to be very effective for the in situ preparation of d‐nucleoside phosphoramidites. These latter compounds could be used for the introduction of 3′,5′‐internucleotide bonds and for the synthesis of DNA fragments both in solution and on a solid support. Removal of the 2‐cyano‐1,1‐dimethylethyl protective group at P(V) could easily be effected by ammonolysis.
A novel synthesis of α‐(phenylthio)aldehydes
Authors: Jansen B. J. M. , Peperzak R. M. , de Groot Ae. 
Published: September 2010

AbstractAddition of methoxy(phenylthio)methyllithium to ketones, followed by rearrangement of the adducts, provides a new method for the preparation of α‐(phenylthio)aldehydes. The rearrangement is stereospecific.
Selective formation of 1,3,4‐trisubstituted and 3,4‐disubstituted trans‐β‐lactams from zinc enolates and imines
Authors: Jastrzebski Johann T. B. H. , van der Steen Fred H. , van Koten Gerard 
Published: September 2010

AbstractA new route for the high yield synthesis (better then 90%) of exclusively trans‐β‐lactams (azetidin‐2‐ones) is reported which involves the 1:1 reaction of an α‐aminoacid ester zinc enolate with an appropriate imine. The reaction can be carried out as a ‘one‐pot’ synthesis as has been demonstrated for the synthesis of trans‐3‐diethylamino‐4‐phenyl azetidin‐2‐one (93% yield). The novel zinc enolates have most likely a Z‐geometry as a result of intramolecular chelate coordination. Evidence has been obtained that in the first step these zinc enolates react with the imine in a highly diastereoselective manner providing the threo aldolate which in a subsequent step undergoes ring closure to the azetidin‐2‐one.