NEIGHBORING GROUP EFFECTS IN A PUMMERER-TYPE REARRANGEMENT - A FACILEENTRY INTO 3,1-BENZOXATHIINS

Arylmethyl sulphoxides treated with trialkylsilyl halide and base unde rgo a Pummerer-type rearrangement to give alpha-siloxy and alpha-chlor osulphides. However, the presence of an ortho hydroxymethyl group resu lts in the exclusive and efficient formation of the alpha-chlorosulphi des, presumably mediated via an intramolecular attack to yield an alko xysulphonium salt. These 2-(hydroxymethyl)aryl chloromethylsulphides c an then be converted into the corresponding 3,1-benzoxathiins via an i ntramolecular cyclisation. Preliminary investigation of the chemistry of these 3,1-benzoxathiins, reveals that in one case, a novel base ind uced ring contraction occurs to yield a benzothiophene.