Improved Method for the Preparation of Benzyllithium

Gilman, Henry; Schwebke, Gerald L.

doi:10.1021/jo01059a031

Cited by 45 publications

(15 citation statements)

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“…However, this experiment is not conclusive, because it was shown in a control experiment that Bu,SnH slowly destroyed the starting material l a . 3 [17]. At -78" in THF, 4,4-dimethyl-2-(methylthio)-l,3-thiazole-5(4H)-th1one (la) was treated with benzyl-and allyllithium reagents.…”

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confidence: 99%

Synthesis and reactions of 2‐(alkylthio)‐4,4‐dimenthyl‐1,3‐thiazole‐5(4H)‐thiones

Shi

Linden

Heimgartner

1994

Helvetica Chimica Acta

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Dedicated to Prof. Heinr G. Viehe on the occasion of his 65th birthday (2.1X.94) Six 2-(alkylthio)-substituted 4,4-dimethyl-l,3-thiazole-5(4H)-thiones were synthesized according to a new method. The reactions of these compounds with allyl-and benzyllithium reagents, 1,3-dipoles, and dimethyl acetylenedicarboxylate proceeded in a similar manner to 2-alkyl-substituted analogues, while methyllithium reacted in a different way yielding trithio-orthoester derivatives.1. Introduction. -A few years ago, due to the lack of appropriate synthetic methods, 1,3-thiazole-5(4H)-thiones were only scarcely known five-membered heterocycles. In 1986, a convenient synthesis of 4,4-disubstituted 1,3-thiazole-5(4H)-thiones was developed by our group [l] [2]. It is based on a reaction involving reactive three-membered rings, the 3-amino-2H-azirines [3] : the addition reaction of thiocarboxylic acids and 3-amino-2H-azirines yielded thiodiamides. On heating with Lawesson reagent [4-61, cyclization of the thioamides afforded 2-substituted 1,3-thiazole-5(4H)-thiones in very good yields [2].Another approach to 1,3-thiazole-5(4H)-thiones is the reaction of carboxylic acids with 3-amino-2H-azirines affording diamides; after thionation of the latter with Heimgartner reagent [7], 2-substituted 1,3-thiazole-5(4H)-thiones were obtained in fair-togood yields [7].However, 1,3-thiazole-5(4H)-thiones with substituents other than alkyl or aryl at C(2) are not accessible by these methods. Since 2-seleno-and 2-thio-substituted 4,5-dihydro-1,3-thiazoles could be useful intermediates in penam syntheses [8] [9], new approaches for the preparation of differently substituted 1,3-thiazole-5(4H)-thiones are still needed. In this paper, a new approach for the synthesis of 2-(alky1thio)-substituted 1,3-thiazole-5(4H)-thiones is described, and some reactions of these compounds with organolithium reagents, 1,3-dipoles, acetylenes, and reducing agents are reported and compared with the 2-alkyl-substituted analogues.

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confidence: 99%

Synthesis and reactions of 2‐(alkylthio)‐4,4‐dimenthyl‐1,3‐thiazole‐5(4H)‐thiones

Shi

Linden

Heimgartner

1994

Helvetica Chimica Acta

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“…Freshly prepared solutions of organolithium compounds in diethyl ether were used. Methyllithium, butyllithium, and phenyllithium were prepared by standard procedures [8] from metallic lithium and methyl iodide, butyl bromide, and phenyl bromide, respectively; benzyllithium was synthesized from benzyl ethyl ether and metallic lithium [8]. The concentration of organolithium reagents was determined by acid-base titration [9].…”

Section: Methodsmentioning

confidence: 99%

Reactions of 2-(α-Haloalkyl)thiiranes with nucleophilic reagents: V. Reactions of 2-(α-Chloroalkyl)thiiranes with organolithium compounds

2010

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2-(α-Haloalkyl)thiiranes reacted with methyl-, butyl-, and phenyllithium to give the corresponding allyl sulfides. The reactions of diastereoisomeric erythro-and threo-2-(1-chloroethyl)thiiranes with phenyllithium were stereospecific, and they afforded (E)-and (Z)-1-phenylsulfanylbut-2-enes, respectively. 3-Chloromethyl-2,2-dimethylthiirane and phenyllithium gave rise to a mixture of 3-methyl-3-phenylsulfanylbut-1-ene and 3-methyl-1-phenylsulfanylbut-2-ene. The reactions of 2-chloromethylthiiranes with phenyllithium and methyllithium in the presence of a catalytic amount of copper(I) iodide (10 mol %) led to the formation of substituted thiiranes as the major products. Mechanisms of the observed transformations are discussed. * For communication IV, see [1]. † Deceased.Unlike oxiranes, reactions of alkylthiiranes with organometallic compounds involve desulfurization or polymerization processes rather than opening of the three-membered ring [2][3][4]. Presumably, desulfurization occurs through intermediate formation of ate complexes and is stereospecific; furthermore, this reaction may be regarded as a method for the preparation of alkenes [2]. On the other hand, there are published data indicating that 2-(chloromethyl)thiirane (Ia) is capable of giving rise to monomeric products of formal chlorine replacement in reactions with organolithium reagents; however, these products have quite specific nature [5, 6] (Scheme 1). Unfortunately, these two examples represent all available information on such reactions which could underlie a convenient procedure for the synthesis of substituted thiiranes. Therefore, in the present work we examined reactions of the simplest organolithium compounds with some 2-(α-haloalkyl)thiiranes in diethyl ether.We found that phenyllithium and butyllithium reacted with 2-(chloromethyl)thiirane (Ia) at a fairly high rate on moderate cooling. Methyllithium was inert up to 0°C, but it did react with compound Ia in the presence of DABCO. Quite surprisingly and contrary to published data, as low-molecular products of these transformations we identified the corresponding allyl sulfides IIa-IIc (Scheme 2). 2-(Bromomethyl)thiirane (Ib) (which is less convenient to handle with) reacted with phenyllithium to give sulfide IIc in a considerably better yield.

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“…19 When these reactions are conducted with very reactive halides such as benzyl or allyl chlorides, significant coupling can occur, leading to a terminal dimeric byproduct. [20][21][22] Similarly, during the conversion of a chlorosilane 3 into a silyllithium 4 (Scheme 1, equation 2), the initially formed silyllithium 4 rapidly re-acts with the starting chlorosilane 3 to form a disilane 5 (Scheme 1, equation (3). In a subsequent step, disilane 5 undergoes reduction to give the silyllithium reagent 4 (Scheme 1, equation 4).…”

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A Quantitative NMR Method for Silyllithium Analysis

Sieburth

2017

Synlett

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A rapid and extremely simple method for silyl anion analysis is presented. The progress of silyllithium reagent preparation can be determined by quenching an aliquot with neat chloro(trimethyl)silane, evaporation, dilution with CDCl3, and direct proton NMR analysis. This procedure is fast, simple, and allows for identification and relative quantification of the starting reagent, intermediates, and the silyllithium product.

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Improved Method for the Preparation of Benzyllithium

Cited by 45 publications

References 2 publications

Synthesis and reactions of 2‐(alkylthio)‐4,4‐dimenthyl‐1,3‐thiazole‐5(4H)‐thiones

Synthesis and reactions of 2‐(alkylthio)‐4,4‐dimenthyl‐1,3‐thiazole‐5(4H)‐thiones

Reactions of 2-(α-Haloalkyl)thiiranes with nucleophilic reagents: V. Reactions of 2-(α-Chloroalkyl)thiiranes with organolithium compounds

A Quantitative NMR Method for Silyllithium Analysis

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