THE REACTION OF CYSTEINE WITH 1,4-BENZOQUINONE: A REVISION.

Article abstract of DOI:10.1016/S0040-4020(01)89833-1

Under carefully controlled conditions, the reaction of L-cysteine with 1,4-benzoquinone leads to a mixture of 1,4-benzothiazine oligomers, arising by decarboxylation and subsequent polymerization of the cyclic quinonimine 1, previously reported as the reaction product.When the reaction was stopped in the early stages by addition of sodium borohydride, work up of the mixture gave, besides the reduced dimer 11, the dihydrobenzothiazine 10, consistent with the intermediacy of the 3-unsubstituted benzothiazine 5.