Etude dans la serie des organosilylazoles : I. Action des halogenures d'alkyle,des chlorures d'acide et des cetones halogenees

The reactivity of organosilylamines of imidazole, pyrazole, 1,2,4-triazole and benzotriazole towards alkyl halides, acidic chlorides and halogenated ketones has been studied. Except for 1-trimethylsilylimidazole, which gives a mixed quaternary salt, reactions with primary halides lead to the corresponding 1-alkylated heterocyclic compounds in high yields; in each case only one isomer is obtained (1-alkyl-1,2,4-triazole and 1-alkylbenzotriazole). Similarly acidic chlorides give 1-acylated derivatives in quantitative yields. Finally α- or β-halogenated ketones show different behaviour and give the addition or substitution products.     

Extremely Efficient Chiral Induction in Conjugate Additions of p-Tolyl alpha-Lithio-beta-(trimethylsilyl)ethyl Sulfoxide and Subsequent Electrophilic Trapping Reactions

Reaction of p-tolyl alpha-lithio-beta-(trimethylsilyl)ethyl sulfoxide with alpha,beta-unsaturated esters gave the conjugate addition products as a single diastereomer. The intermediate enolates were subsequently trapped with various alkyl halides or aldehydes to give the products with extremely high stereoselectivity. The reaction with alpha,beta-unsaturated ketones also proceeded with high diastereoselectivity. Protolysis of the enolates derived from the alpha-methyl-alpha,beta-unsaturated esters gave the products with high stereoselectivity. The stereo- and regioselective elimination of the sulfinyl group gave chiral homoallylic carboxylates.     

Etude de l'obtention d'enoxysilanes par action du triethylsilane sur des cetones enolisables,aliphatiques ou cyclaniques,en presence de catalyseurs au nickel

The preparion of alkoxysilanes and alkenoxysilanes has been achieved by the reaction of enolizable aliphatic or cyclic ketones with triethylsilane in the presence of nickel catalysts. For some catalysts, the reaction can be directed to give exclusively one or the other of these derivatives. The use of certain nickel catalysts gives very high yields of alkenoxysilanes, and this has been closely investigated.     

Alkylation d'enamines par les halogeno-5 ene-3 ynes-1

The alkylation of several enamines of cyclanones with 5-halogeno 3-ene 1-ynes 1 gives a mixture of isomeric ketones 3 and 4. The composition of this mixture is independent of the enamine but is related to the nature of the halide 1. The primary halides lead essentially to ketones 3 and the secondary halides give predominantly 4. Both ketones are always formed via an initial C-alkylation; a mechanism taking account of the experimental results is proposed.     

Cross-coupling reaction of alpha-chloroketones and organotin enolates catalyzed by zinc halides for synthesis of gamma-diketones

The reaction of tin enolates 1 with alpha-chloro- or bromoketones 2 gave gamma-diketones (1,4-diketones) 3 catalyzed by zinc halides. In contrast to the exclusive formation of 1,4-diketones 3 under catalytic conditions, uncatalyzed reaction of 1 with 2 gave aldol-type products 4 through carbonyl attack. NMR study indicates that the catalyzed reaction includes precondensation between tin enolates and alpha-haloketones providing an aldol-type species and their rearrangement of the oxoalkyl group with leaving halogen to produce 1,4-diketones. The catalyst, zinc halides, plays an important role in each step. The carbonyl attack for precondensation is accelerated by the catalyst as Lewis acid and the intermediate zincate promotes the rearrangement by releasing oxygen and bonding with halogen. Various types of tin enolates and alpha-chloro- and bromoketones were applied to the zinc-catalyzed cross-coupling. On the other hand, the allylic halides, which have no carbonyl moiety, were inert to the zinc-catalyzed coupling with tin enolates. The copper halides showed high catalytic activity for the coupling between tin enolates 1 and organic halides 7 to give gamma,delta-unsaturated ketones 8 and/or 9. The reaction with even chlorides proceeded effectively by the catalytic system.     

Addition regioselective d'enolates de cetones aux α-enones: Influence des facteurs steriques sur l'orientation et la reversibilite des reactions

Regio and stereochemistry in the addition of preformed magnesium and lithium ketone enolates (1 to 8) to α-enones (10 and 11) have been examined. When the substitution degree of the enolate is increased the formation of δ-diketone is favoured; nevertheless a good efficiency in the synthesis of the γ-ethylenic β-ketols (1-2 addition) is obtained via bromomagnesium enolates (EMgX) under kinetic conditions. Lithium enolate (ELi) and, chiefly magnesium enolates (E₂MgX) give preferentially the Michael addition. Reversibility from 1-2 to 1-4 addition is commonly observed but the stereochemistry, if any, of the diastereoisomeric δ-diLetones may be quite different when using EMgBr or E₂Mg as starting enolates.     

Condensations en milieu aprotique d'enolates de cetones sur le chloro-1 cycloheptene en presence de bases—I: Synthese de tricyclo[7.n.0.02,8]alcene-7 ols-1

Condensation, in aprotic media, of enolates of alicyclic ketones with 1-chloro cycloheptene leads to tricyclo[7.n.0.0^2,8]7-alcene-1 ols. 1,2-Cycloheptadiene is probably involved as intermediate in these reactions. Solvent effects are studied.     

Condensations aryniques d'enolates de cetones—VII: Synthese generale de benzocyclenones non substituees; Mecanisme de condensation du benzyne sur les enolates de cetones

Some 1,2-benzocyclene-3 ones, so far, unknown have been prepared easily by condensation of the benzyne on the enolates of cyclanones. The general mechanism of the condensation of the benzyne on the enolates of alicyclic ketones in aprotic medium is proposed.     

Alkylations en α de fonctions organiques par l'intermédiaire de compostés organostanniques

Organotin enolates and α-organotin substituted nitriles or esters which are generally easy to obtain, can be used to alkylate α to functional groups.In the case of organotin enolates, heating with alkylating agents, usually gives monoalkylated products in very good yields: numerous examples with ketones and aldehydes are described.With α-organotin substituted nitriles and esters, direct alkylation does not occur, but good results can be obtained in the presence of either magnesium or lithium bromide, or after a metal exchange reaction with a Grignard or lithium reagent.     

Coupling reaction of alkyl chlorides with silyl enolates catalyzed by indium trihalide

Indium(III) halide catalyzed not only the coupling of alkyl chlorides with silyl enolates derived from esters, ketones, and aldehydes to give a variety of alpha-alkylated carbonyl compounds but also one-pot, three-component reactions of aldehyde enolate, alkyl chloride, and allylsilane or alkynylsilane.     

Synthesis of α,β‐Unsaturated Ketones and Esters Using Polymer‐supported Selenium Bromide

Treatment of the polymer‐supported α‐phenylseleno ketones and esters prepared from polymer‐supported selenium bromide with ketone and ester enolates with hydrogen peroxide afford α,β‐unsaturated ketones and esters in good yields and high purities.     

O-Silylated enolates in organic synthesis: α-Alkylation of carbonyl compounds by 1,3-dithienium fluoroborate.

The O-silylated enolates of ketones, aldehydes, esters, and lactones can be regiospecifically alkylated by 1,5-dithienium fluoroborate to give the selectivity protected β-dicarbonyl compounds.     

Chloracylierung und Bromacylierung von Carbonylverbindungen: Eine in Vergessenheit geratene Carbonylreaktion. I. Präparative Anwendungsbreite

Chloroacylation and bromoacylation of carbonyl compounds: A forgotten carbonyl reaction. I. Scope of the reaction Aliphatic, α,β-unsaturated and aromatic aldehydes as well as aliphatic ketones react with acyl halides to (α-haloalkyl)esters. These bifunctional derivates contain two leaving groups of different reactivity. The scope of this scarcely of this scarcely known carbonyl reaction is discussed.     

Enantioselective Generation and Diastereoselective Reactions of Chiral Enolates Derived from α-Heterosubstituted Carboxylic Acids. Preliminary Communication

Dioxolanones 7 and 8a and oxazolinones 9a derived from pivalaldehyde and lactic acid, mandelic acid, and proline, respectively, furnish chiral enolates of type 3 by deprotonation with LDA. Reactions of these enolates with alkyl halides, aldehydes, and ketones (→ 8b, 9b, 11–13) are highly diastereoselective. Thus, the overall enantioselective α-alkylation of chiral, non-racemic α-heterosubstituted carboxylic acids (4 → 6) is realized.     

Indium-catalyzed coupling reaction between silyl enolates and alkyl chlorides or alkyl ethers

The coupling reactions of alkyl chlorides with silyl enolates catalyzed by InBr₃, and the coupling reactions of alkyl ethers with silyl enolates catalyzed by the combined Lewis acid of InBr₃/Me₃SiBr are described. In both reaction systems, various types of silyl enolates were used to give corresponding α-alkylated esters, ketones, carboxylic acids, amides, thioesters, and aldehydes.     

Anion radicals and dianions as electron transfer reagents

The catalytic regeneration of depolarizers by certain substrates has been demonstrated by means of cyclic voltammetry. As depolarizers we have employed anion radicals of aromatic hydrocarbons, heteroaromatic compounds, ketones, esters, nitriles, and olefins, and dianions of aromatic hydrocarbons, heteroaromatic compounds, ketones, and esters. As substrates we have investigated simple aromatic and aliphatic halides, 1,2- and 1,3-dihalides, carbon dioxide, and activated olefins. A requirement for the observation of a catalytic wave is that the reduced substrate undergoes a practically irreversible reaction after the reaction with the reduced depolarizer; for simple halides it is a cleavage reaction, for 1,2- and 1,3-dihalides an elimination, for carbon dioxide an addition, and for activated olefins a coupling. Electrochemical investigations of these kinds of reactions may be of interest in connection with the mechanism of several types of reactions in organic chemistry.     

Condensations aryniques d'enolates de cetones—VI: Synthese de phenyl-2 cyclohexanones tricyclo[6,n,0,02,7]trienes-2,4,6 ols-1 diversement substitues

The condensation of benzyne in aprotic medium with the enolates of the 2,2,6-trimethyl, 3,3,5,5-tetramethyl, 4-4-dimethyl, 4-methyl, 4-t-butyl cyclohexanones as well as with those of α-tetralone and α-benzosuberone leads to the corresponding α-phenyl ketones and several tri and tetracyclic benzocyclobutenols.     

Iridium‐Catalyzed Enantioselective Allylic Substitution of Aliphatic Esters with Silyl Ketene Acetals as the Ester Enolates

Enantioselective allylic substitution with enolates derived from aliphatic esters under mild conditions remains challenging. Herein we report iridium‐catalyzed enantioselective allylation reactions of silyl ketene acetals, the silicon enolates of esters, to form products containing a quaternary carbon atom at the nucleophile moiety and a tertiary carbon atom at the electrophile moiety. Under relatively neutral conditions, the allylated aliphatic esters were obtained with excellent regioselectivity and enantioselectivity. These products were readily converted into primary alcohols, carboxylic acids, amides, isocyanates, and carbamates, as well as tetrahydrofuran and γ‐butyrolactone derivatives, without erosion of enantiomeric purity.     

Exclusive alpha-coupling in the aldol reaction of unsaturated trimethylsilyl esters: an efficient and practical direct synthesis of unsaturated beta-hydroxy acids

The lithium enolates of trimethylsilyl but-3-enoate and 3-methylbut-3-enoate reacted with aldehydes and saturated or aromatic ketones at -70 degrees C to give exclusively the alpha-condensation products in excellent yields. The unsaturated beta-hydroxy acids thus obtained were directly identified, and the usual conversion into their methyl esters with diazomethane was not necessary. Unsaturated ketones underwent Michael reaction through alpha-addition leading to the unsaturated 5-oxo acids.     

A new synthetic route to α-alkylacrylic esters and α-alkylacrylonitriles

α-Alkylacrylic esters and α-alkylacrylonitriles have been synthesized by cracking their cyclopentadiene adducts. The latter were derived by treatment of the lithium enolates of cyclopentadiene-blocked acrylates or acrylonitriles with alkyl halides.