Neighbouring Group Effects in a Pummerer-Type Rearrangement: A Facile Entry into 3,1-Benzoxathiins

Article abstract of DOI:10.1016/0040-4020(95)00315-Y

Arylmethyl sulphoxides treated with trialkylsilyl halide and base undergo a Pummerer-type rearrangement to give α-siloxy and α-chlorosulphides.However, the presence of an ortho hydroxymethyl group results in the exclusive and efficient formation of the α-chlorosulphides, presumably mediated via an intramolecular attack to yield an alkoxysulphonium salt.These 2-(hydroxymethyl)aryl chloromethylsulphides can then be converted into the corresponding 3,1-benzoxathiins via an intramolecular cyclisation.Preliminary investigation of the chemistry of these 3,1-benzoxathiins, reveals that in one case, a novel base induced ring contraction occurs to yield a benzothiophene.