Cyclic sulphones. Part XV. Benzo-and dibenzo-thiopyran SS-dioxides, ‘active methylene’ compounds in substitution and condensation reactions

Abstract

2H-Benzo[b]thiopyran 1,1-dioxide, 1H-benzo[c]thiopyran 2,2-dioxide, dibenzo[b,d]thiopyran 5,5-dioxide, and thioxanthen 10,10-dioxide are methylated by methyl iodide under mild basic conditions. 2H-Benzo[b]thiopyran 1,1-dioxide reacts analogously with 2,4-dinitrochlorobenzene. Benzylidene derivatives are obtained by reacting the two benzothiopyran and thioxanthen SS-dioxides with para-substituted benzaldehydes. This behaviour is discussed and compared with that of other sulphonyl-substituted carbon acids.