Unexpected Formation of the Arcyriacyanin System by Condensation of a 3-Bromo-4-(indol-3-yl)maleimide with (2-Nitrophenyl)acetates

Abstract

The reaction of an N-protected 3-bromo-4-(indol-3-yl)maleimide with methyl (2-nitrophenyl)acetates in the presence of base affords condensed cycloheptatriene derivatives which can be transformed into arcyriacyanin-type alkaloids. The unusual reaction sequence implies a heptatrienyl–cycloheptadienyl anion rearrangement followed by a 1,5-sigmatropic shift to yield the thermodynamically more stable cycloheptatriene derivative.