C. G. Moore, B. R. Trego
1962
Citations
0
Influential Citations
36
Citations
Journal
Tetrahedron
Abstract
Abstract The rate and course of reaction of triphenylphosphine (Ph 3 P) with organic sulphur compounds (R·S x ·R′; R,R′ = alkyl or alkenyl, x = 2 or 4) at 80° or 140° depend on the nature of R and R′ and on the reaction medium. Dialkyl- and diaralkyl tetrasulphides (RR′ = iso-Pr; n-Bu; T-Bu; PhCH 2 ) yield triphenylphosphine sulphide and dialkyl- or diaralkyl disulphides which are resistant to further attack by Ph 3 P, even at 140°. Dialkenyl- and alkenyl-alkyl disulphides at 80° undergo a less facile desulphuration to give monosulphides which result from the allylic rearrangement of an alkenyl group; the yield of allylically-unrearranged monosulphide is negligible. The rates of the Ph 3 P-disulphide reactions increase with increasing solvent polarity and decrease with increasing alkyl substitution at γ-carbon atoms of the alkenyl groups or the α-carbon atom of the alkyl groups. The Ph 3 -P-tetrasulphide reactions are believed to involve nucleophilic substitutions at the SS bonds, initially by the reagent and then by a resultant incipient alkanethiolate or alkaneperthiolate ion. The rates and course of the Ph 3 P-disulphide reactions are only consistent with nucleophilic attack of the Ph 3 P on sulphur yielding an intimate ion-pair which then undergoes an almost exclusive S N i′ process.