Facile synthesis of 4,6-dihydrothieno[3,4-b]thiophene 5,5-dioxide. A synthetic equivalent of 2,3-dihydro-2,3-dimethylenethiophene

Abstract

4,6-Dihydrothieno[3,4-b]thiophene 5,5-dioxide 4, a stable precursor of 2,3-dihydro-2,3-dimethylenethiophene 3, conveniently prepared from 4-bromo-3-chloro-2,3-dihydrothiophene S,S-dioxide, can easily be alkylated and loses SO₂ upon heating so that 4 serves as a useful synthetic equivalent of 3.