摘要:
Application of the Hemetsberger reaction to ethyl 4-benzyl-7-formyl-2,3-dihydro-1,4-benzoxazine-2-carboxylate (1) or acetate (2) afforded a mixture of ethyl 2,3,4,6-tetrahydro-[1,4]oxazino[2,3-f]indole-7-carboxylate derivatives 3 or 4 and ethyl 2,3,4,9-tetrahydro[1,4]oxazino[3,2-g]indole-8-carboxylate derivatives 5 or 7, with the "linear" derivatives pre-dominant. Michael addition of tert-butyl acrylate to the indole nitrogen atom of 3, 4 and subsequent electrophilic cyclisation gave access to tetracyclic compounds 24, 25, (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.