Syntheses with metallated thioacetals and orthothioformates

Abstract

Thioacetals and orthothioformates, compounds having the general formula HC(R)(SR)z with R = H , S R , CH3, or C6H5 and R = CZH5 or C6H5, were metallated by means of alkali amides in liquid ammonia. The metallated derivatives were A) alkylated, B) converted with ketones (successfully only when R = H and R = C6H5), and C ) ethylthiolated by means of diethyldisulphide (only when R = H , SR', or C6H5). The results of the reactions are summarized in Tables I-VI, VLII, and IX. Similar conversions were impossible with common acetals or orthoformates (notably CH2(0C2H 5)2, C6H5 -CH(OCZH~)Z, and CH(OCzH&). The easy metallation of the thiocompounds is attributed to d-orbital participation of sulphur, which probably lowers the activation energy of the metallation reaction and enhances the stability of the carbanions.The new reactions in principle enable the synthesis of aldehydes from formaldehyde, of methyl ketones from acetaldehyde, of phenyl ketones from benzaldehyde, and of carboxylic acids from formic acid.Upon standing, solutions of NaC(SC2H5)3 and NaC(SC&I5)3 in liquid ammonia slowly decompose, yielding compounds of the type (RS)zC = C(SR')2. The transient occurrence of a carbene :C(SR)z, formed by splitting-off of thiolate from the carbanion 0 C(SR)3, is discussed.In a preliminary communication we reported that formaldehyde diethylthioacetal I can be metallated easily with sodamide or lithium amide in liquid ammonia and then alkylated. I I. The metallation reactionIn the meantime we studied the metallation reaction somewhat more closely, including also formaldehyde-diphenylthioacetal 11, acetaldehydediethylthioacetal 111, acetaldehyde diphenylthioacetal IIIa, benzaldehydediethylthioacetal IV, triethyl orthothioformate V, and triphenyl orthothioformate VI in the investigation.J. F. Arens, M. Froling, and A. Froling, Rec. trav. chim. 78, 663 (1959).

Bis(phenylthio)methane

“…Nevertheless, there are a number of novel transformations involving derivatives of (1) and it is the applications of these reactions that comprise the major portion of the present account. 8 Reaction of (2) with primary alkyl halides gives high yields of phenyl thioacetal derivatives of aldehydes (3) (eq 2). (3) (3) hydrolysis RCH 2 CHO (PhS) 2 CHCH 2 R Metalation of (1) and Nucleophilic Reactivity of (2).…”

Tris(phenylthio)methane

“…The reagent, in THF or ether solution, is quantitatively converted to its lithiated derivative with 1 equiv of n-Butyllithium at −78 • C. It has also been converted to its sodium and potassium salts with the corresponding alkali metal amides. 4 The lithiated species is a useful nucleophilic carboxylating reagent for a variety of organic electrophiles. This chemistry is discussed in the article Tris(phenylthio)methyllithium.…”