Elimination and addition reactions. Part 38. Synthesis and reactivity of diene-bis-sulphonium salts

Abstract

Buta-1,3-diene-1,4-bis-sulphonium salts have been synthesised from buta-1,3-diyne. Reactions with oxygen, sulphur, nitrogen, and carbon nucleophiles have been examined. Except for primary amines and anions of enolisable carbon acids, 1,4-addition and subsequent elimination of the sulphonium group is observed in all cases. Subsequent addition occurs with alkoxide and thiolate ions, and is followed by dealkylation of the remaining sulphonium group or its displacement by allylic substitution.

When hydroxy-thiols or dithiols are used, a second intramolecular addition at carbon 4 yields cyclic products. Such products are not formed from hydroxy-amines. The mono-adducts formed from alkenylthiols are potentially capable of, but do not undergo, intramolecular Diels–Alder reactions under a variety of conditions. Neither are intramolecular reactions found in the adduct with 2-methoxycarbonylethanethiol or in the bis-adduct formed by subsequent additions of azide ion and propene-3-thiolate ion.