Thermal rearrangement of 2,2,4,4-tetramethylthietan-3-one 1-oxide; a reaction related to the ring expansion of the penicillin S-oxides

Abstract

When the title compound (4) is heated for 1 ½ h in refluxing benzene a mixture of ring-expanded products, (6a)(25%) and (7)(67%), is obtained. In acetic anhydride, compounds (4) gives the acetate (6b) 77% as the only significant product, and in norbornene, dinorbornyl sulphoxide (12a) 35% is formed. In the presence of a silylating agents the sulphenic acid intermediate (5a) can be trapped as the trimethylsilyl derivative (5b) but this, in turn, under-goes a thermal rearrangement to give the enol ether (13).