Photo-irradiation of α-halo carbonyl compounds: a novel synthesis of α-hydroxy- and α,α′-dihydroxyketones

The reaction of α-halo ketones (α-iodocycloalkanones, α-bromocycloalkanones, α-iodo-β-alkoxy esters, and α-iodoacyclicketones) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketones in good yields. For α-bromoketones, it was found that α-hydroxylation does not occur. However, α-bromoketones were converted into α-hydroxyketones in the presence of KI. In the case of α,α′-diiodo ketones, α,α′-dihydroxyketones, which up to now have scarcely been reported, were obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′-dihydroxyketones.     

Chemoselective mono halogenation of β-keto-sulfones using potassium halide and hydrogen peroxide; synthesis of halomethyl sulfones and dihalomethyl sulfones

The synthesis of α-halo β-keto-sulfones using potassium halide and hydrogen peroxide as a chemoselective mono halogenation reagent and the synthesis of α,α-symmetrical and asymmetrical dihalo β-keto-sulfones and α-halo, α-alkyl and β-keto-sulfones is described. Base induced cleavage of α-halo β-keto-sulfones, α,α-dihalo β-keto-sulfones, and α-halo, α-alkyl β-keto-sulfones afforded the corresponding halomethyl sulfones, dihalomethyl sulfones and haloalkyl sulfones.     

Reactivity of α-chloro-aldimines

A series of secondary N-1-(2-chloroalkylidene)amines has been prepared by condensation of disubstituted acetaldehydes with primary amines followed by chlorination with N-chlorosuccinimide in carbontetrachloride. A study of the reactivity of these N-homologues of α-chloroaldehydes is described. Treatment of the title compounds with sodium methoxide in methanol gave high yields of α,β-unsaturated aldimines. However, N-1-(2-chloro-2-methylpropylidene)amines afforded a mixture of elimination and rearrangement products, which proceeded via an aziridine intermediate. On the other hand, α-phenyl-substituted α-chloro aldimines on treatment with methoxide in methanol underwent α-substitution, consistent with an S_N1 mechanism. Powerful nucleophiles such as sodium thiophenolate in methanol and sodium azide in acetone caused α-substitution. Reaction of α-chloro aldimines with Grignard reagents produced coupling of two aldimine units or α-alkylation. Finally the reactivity of α-chloro aldimines was compared with the reactivity of the corresponding oxygen-analogues, i.e. α-chloro aldehydes.     

Organocatalyzed asymmetric α-hydroxyamination of α-branched aldehydes: asymmetric synthesis of optically active N-protected α,α-disubstituted amino aldehydes and amino alcohols

Enantioselective direct α-hydroxyamination and α-aminoxylation of α-branched aldehydes using a proline-derived tetrazole catalyst is described herein. α-Hydroxyamination adducts with up to 90% ee were obtained by the reaction of nitrosobenzene with unactivated α-branched aldehydes under mild reaction conditions.     

α-乙酰基二硫缩烯酮α碳原子的酰化反应

进行了α-乙酰基二硫缩烯酮与酰氯的酰化反应. 以干燥的二氯甲烷为溶剂, 在四氯化钛催化下, α-乙酰基环二硫缩烯酮(1)可与脂肪及芳酰氯(2)反应, 在化合物1的α-碳原子上发生酰化反应, 以较高的产率生成各种α-乙酰基-α-酰基二硫缩烯酮(3).     

Inorganic chemistry of vitamin B12; by J.M. Pratt. Academic Press,London and New York, 1972, £6.00 net

Action of dimethyllithium cuprate on α,α-dichloro esters at room temperature leads to the formation of α-chloro α-methyl esters together with non chlorinated α-methyl esters; the same reaction performed at ?70° produces α-chloro ester enolates which upon heating to room temperature are transformed into α-methyl ester enolates. The reaction is applied to β-functional α,α-dichloro esters and one α,α-dichloro ketone.     

Synthesis and Diels-Alder reactions of α-fluoro- and α-trifluoromethylacrylonitriles

A novel synthetic method for the preparation of α-fluoro- and the still unknown α-trifluoromethylacrylonitriles is elaborated. The reaction of α-fluorovinylbromides and α-trifluoromethylvinylbromides with CuCN leads to the title compounds in good to high yields. While the α-fluoroacrylonitriles were isolated as mixture of Z/E-isomers, the α-trifluoromethylacrylonitriles were obtained as pure Z-isomers. The α-trifluoromethylacrylonitriles are shown to be excellent dienophiles for Diels-Alder reactions.     

The conformation of α-substituted cyclohexanones. Group VI-A substituents

α-Phenylthio-, a α-phenylsulfono- and α-phenylseleno-cyclohexananone have the prefered conformation with the substituent axial whereas the α-phenoxy and α-phenylsulfoxo-cyclohexanones have the substituent equatorial.     

正丁胺对晶态层状苯乙烯基膦酸-磷酸氢锆的插层研究

合成了晶态层状有机-无机多功能材料苯乙烯基膦酸-磷酸氢锆(α-ZPPVPA),并研究了正丁胺(BA)对α-ZPPVPA的插层性能。用元素分析、XRD、IR、TG、SEM和TEM等分析方法对α-ZPPVPA及其插层化合物α-ZPPVPA-BA进行了结构表征和形貌分析。结果表明,正丁胺成功地插入了α-ZPPVPA层板之间,层间距为2.41 nm,正丁胺的插入使α-ZPPVPA的层间距(1.66 nm)增大了0.75 nm,插入的正丁胺在α-ZPPVPA中呈双分子层排列,且苯乙烯基侧链不饱和双键的存在不影响α-ZPPVPA与正丁胺的插层反应。     

Synthesis,isolation, and chromatography of perdeuterated α-1,2,3,4,5,6-hexachlorocyclohexane

Perdeuterated α-1,2,3,4,5,6-hexachlorocyclohexane (α-PDHCH) was synthesized and isolated in pure form. α-PDHCH was baseline separated from unlabeled α-HCH by high resolution gas chromatography on different stationary phases. α-PDHCH was also resolved into its enantiomeric forms by application of a chiral GC phase. Furthermore, chiral chromatography of a mixture of labeled α-PDHDH and unlabeled α-HCH resulted in four peaks. Standard solutions of α-PDHCH are recommended both as recovery standard for sample clean-up and as internal standard for the quantitation of chlorinated hydrocarbons with GC/MS or GC/ECD in environmental samples.     

Chaperone Function of Rat Lens α-Crystallin

A solution of γ-crystallin became turbid upon beating at 65 °C for 30 minutes; however, addition of α-crystallin suppressed this thermal aggregation. It was found the effective chaperone function could be achieved with the molar ratio of α/γ greater than 1/20. In terms of crystallin subunit, five molecular α-crystallin subunits could afford chaperone for one molecular γ-crystallin. The gel filtration profile of the sample solution, containing α- and γ-crystallins and preincubation at 65 °C for 30 minutes, showed complex formation between α- and γ-crystallins, indicating α-crystallin was bound to thermally denatured γ-crystallin. A 1-anilinonaphthalene-8-sulfonic acid (ANS) fluorescence study showed that α-crystallin has more hydrophobic regions exposed after thermal incubation. In the presence of urea, both the α-crystallin chaperone activity and the ANS fluorescence intensity decreased. Accordingly, hydrophobic regions of α-crystallin play an indispensible role in its chaperone activity.     

New Possibilities of the Kabachnik–Fields and Pudovik Reactions in the Phthalocyanine-Catalyzed Syntheses of α-Aminophosphonic and α-Aminophosphinic Acid Derivatives

The results of systematic studies demonstrated wide possibilities of the three-component Kabachnik–Fields and two-component Pudovik reactions catalyzed by metal phthalocyanines in the synthesis of structurally diverse α-aminophosphonates. Extension of this catalytic method to the synthesis α-aminophosphinates gave rise to a series of α-amino- and α-hydrazinophosphinates based on biogenic amino acids. A number of α-hydrazinophosphonates showed a good antioxidant activity.     

Stereocontrolled synthesis of α-furyl amines and α-furyl carbinols

A novel stereocontrolled synthesis of optically active α-furyl amines and α-furyl carbinols from α,β-aziridine and α,β-epoxy aldehydes using a one-pot aldol reaction-intramolecular enolcyclization is described.     

Polymerization and copolymerization of α-methacrylophenone

Under a variety of conditions it has not been possible to induce the free-radical-initiated homopolymerization of α-methacrylophenone (α-MAP). The only product isolated from such efforts was the Diels-Alder dimer of the monomer. A Mayo-Lewis plot of the free-radical copolymerization of α-MAP and styrene shows considerable scatter but the copolymer composition indicates that an α-MAP unit can add to itself. These results have been ascribed to a penultimate effect. α-MAP is homopolymerized by dimsylsodium or n-butyllithium. Attempted copolymerization of α-map and styrene with n-butyllithium produces >95% α-MAP. Unexpectedly, α-MAP does not homopolymerize with lithium dispersion, but does react in the presence of styrene to give product containing a relatively small amount of α-MAP.     

Synthetic transformations of higher terpenoids: XXII. Reactions of lambertianic acid derivatives with organozinc reagents obtained from ethyl bromoalkanoates

Reactions of 16-cyanomethyllambertianate with organozinc reagents obtained from ethyl esters of α-bromoacetic, α-bromopropionic, and α-bromobutyric acids gave the corresponding enaminoesters, β-ketoesters, and β-hydroxyesters of labdanoids whose yield depended on the reaction conditions and the structure of the α-bromoester. By Reformatsky reaction of 16-formylmethyllambertianate with α-bromoesters of carboxylic acids stereoisomeric β-hydroxyesters of labdanoids were synthesized.     

Synthesis of glycosyl disulfides containing an α-glycosidic linkage

A wide range of symmetrical and unsymmetrical glycosyl disulfides is synthesized with focus on the use of α-glycosyl thiols. Oxidation of α-glycosyl thiols with iodine leads to symmetrical α,α-glycosyl disulfides, while unsymmetrical disulfides are readily synthesized from α- and β-glycosyl thiols under the action of DDQ. Thus, glycosyl disulfides containing at least one α-glycosidic linkage are made available.     

Reactions with α-substituted cinnamonitriles. A novel synthesis of hexa-substituted pyridines

Whereas acetoacetanilide (II) reacted with α-cyano- and α-benzoylcinnamonitrile derivatives Ia-e to give hexa-substituted pyridines III and V, it reacted with α-carboxamido- and α-thiocarboxamidocinnammonitrile derivatives If-h to afford penta-substituted pyridines VI. One mole of acetonedicarboxylic acid dianilide (VII) reacted with two moles of each of α-cyano- and α-thiocarboxamidocinnamonitriles Ia,b,f,g to yield the dipyridyl ketones VIII and IX, respectively. On the other hand, α-benzoyl- and α-ethoxycarbonylcinnamonitriles Ic,d,i,j reacted with VII in equimolecular ratio to give the pyran derivaties X and XI, respectively. Several schemes were proposed to illustrate reactions steps. The structures of the synthesized compounds were proved by chemical and spectral methods.     

Catalytic asymmetric synthesis of cyclic α-alkyl-amino acid derivatives by C,N-double alkylation

Catalytic asymmetric synthesis of various cyclic α-alkyl-amino acid derivatives having a tetrasubstituted α-carbon, such as α-alkylprolines has been accomplished by asymmetric phase-transfer C-alkylation of α-alkyl-amino acid derivatives and subsequent intramolecular N-alkylation.     

Synthesis of α-Alkoxylidene Lactones

The α-formylation of α-lactones and the high yield conversion into their respective α-alkoxylidene lactones are described     

Reactivity of α-arylseleno-aldehydes towards halogens and benzeneselenenyl chloride

Chlorination of α-seleno-aldehydes bearing an α-hydrogen gives selenium dichlorides which decompose into α-chloro α-seleno-aldehydes and α-chloroenal. Bromination, in all cases, and chlorination for the other α-seleno-aldehydes lead to the α-halogenoaldehydes.