[2,3] Fused indoles. Synthesis of β-carbolines and azepino[4,5-b]indoles from 3-(2-alkylindol-3-yl)-2-azidoacrylates1

Abstract
Decomposition of the azidoacrylates (6) derived from 2-substituted indole-3-carbaldehydes gives pharmacologically important β-carbolines [(8), (11)], azepino[4,5-b]indoles (13), or enamines (14) depending on the conditions. The formation of azepinoindoles, shown to proceed by cyclisation of the initially formed enamines, represents a new reaction of vinyl azides which is particularly favoured in the indole series.