A NEW SYNTHETIC APPROACH TO SOME FUNCTIONALIZED CYCL[3.2.2]AZINE DERIVATIVES

Dehydrogenation of some ethyl 4-oxo-1H-8,8a-dihydro-1,4-thiazino[3,4,5-cd]indolizine-1-carboxylates with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) were examined. No simply dehydrogenated products such as 4-oxo-1H- and 4-oxo-8H-1,4-thiazino[3,4,5-cd]indolizines or their full conjugated enol forms could be obtained, but ethyl cycl[3.2.2]azine-1-carboxylates were directly obtained via the cyclization and the subsequent desulfurization of the 4H-1,4-thiazine ring in the dehydrogenated intermediates.