Thermal racemisation of 1,4-thiazine oxides: evidence for a sigmatropic pathway
Abstract
The thermally induced racemisation of methyl (4R,6R)-9,9-dimethyl-7-oxo-8-oxa-4-thia-1-azabicyclo-[4,3,0]non-2-ene-3-carboxylate 4-oxide (5) probably involves the intermediacy of the sulphenic acid (9), which is formed by a sigmatropic hydrogen shift.