NOVEL REACTION OF 2-METHYLENEBENZOTHIAZOLINES WITH 3-(2, 3-DIPHENYL-2-CYCLOPROPENYLIDENE)PENTANE-2,4-DIONE: FORMATION OF 3a,9-DIHYDROCYCLOPENTA[b] [1,4]BENZOTHIAZINES
, generated in situ from the corresponding 2-methylbenzothiazolium bromide and triethylamine, with methylenecyclopropenes gave a variety of products, cross-conjugated systems, spiro-cyclopentafurans and/or cyclopentabenzothiazines, depending on the nature of substituents of the methylenecyclopropenes. The reaction pathways for the formation of products are also described.