Neighboring Group and Substituent Effects in Organosulfur Compounds

Abstract

Thioether groups participate in nucleophilic substitution reactions at adjacent carbon atoms, in the addition of alkane and arertesulfenyl halides onto olefnic double bonds, and in elimination reactions which lead to olefins and which proceed via intermediate episuvoniurn ions.Studies of alkylthioacrylic acid derivatives, which are readily synthetized because of the neighboring group efect, show that the presence of thioether groups in the u-position of acrylic acid systems leads to particularly high reactivity in "head-to-head" dimerizations.

Thietanium Ion Formation from the Food Mutagen 2-Chloro-4-(methylthio)butanoic Acid

“…The mass spectra (Figure 2B,C) of the products formed were the methyl esters of the expected products formed by reaction of 1-methyl-2-thietaniumcarboxylic acid with 4-chlorophenol. The products were identified as 2-(4-chlorophenoxy)-4-(methylthio)butanoic acid (5) and 4-(4chlorophenoxy)-2-(methylthio)butanoic acid (6). Acids 4, 5, 6, and 10 were formed in the ratio 2:1:1:2, based on their relative peak areas in the total ion chromatogram.…”

“…Internal displacement of the R-chlorine by the thioether sulfur may result in formation of 1-methyl-2-thietaniumcarboxylic acid (2) (Scheme 1). Neighboring-group effects in organosulfur compounds are well-known, particularly with 2-haloalkyl thioethers (6). The transition state for thioether participation requires that the thioether sulfur, the R-carbon bearing the leaving group, and the leaving group are in a linear antiperiplanar array; thus, a general requirement for thioether neighboring-group participation is a structure that is sufficiently flexible to accommodate the anti-periplanar transition state or a rigid ring system that holds the participating atoms in the proper configuration.…”

New class of cationic ring‐opening polymerizations of 2,2‐diphenyl‐1,3‐oxathiolanes accompanying quantitative elimination of benzophenone

“…Instead, we assume a three‐membered sulfonium cation ( III ), which could be formed by intramolecular attack of the sulfur atom at the β‐position in II to the α‐carbon, causing a nucleophilic substitution in which benzophenone acts as a leaving group. Such neighboring group participation by sulfur atoms is well known in the S N 2 reaction of β‐thio‐haloalkanes 6. When the next monomer attacks III , the substitution could occur at both the α‐position and β‐position of III .…”

New Sulfenyl Chloride Chemistry: Synthesis, Reactions and Mechanisms toward Carbon-Carbon Double Bonds

“…The reactivities of compounds containing sulfur-chlorine bonds have been extensively studied [55]. It was therefore not considered necessary to do an exhaustive study of the chemistry of 2, 3 and 4 but a few representative reactions were investigated.…”