Cycloaddition reactions of 2H-benzo[b]thiete and conjugated cyclic dienes

2H-Benzob]thiete 1 reacts with cyclopentadiene 3 in consecutive 8π + 2π]cycloadditions yielding the condensed heterocycles 6–8 . Tetracyclone 9 on the other hand gives only the monoadduct 10 . An 8π + 8π]cycloaddition can be observed for 1 and diphenylisobenzofuran 11 . The related π system 13 shows again consecutive 477π + 27π]processes ( 1 + 13 ← 14, 15 ).