Studies on the syntheses of heterocyclic compounds. Part 744. A synthesis of 1-benzazocin-5-ones from 2,3-dihydro-1H-pyrrolo[1,2-a]indoles; a synthetic approach to the mitomycins

Abstract

On reduction with sodium borohydride in acetic acid, the 2,3-dihydro-1H-pyrrolo[1,2-a]indoles (4) and (5) were converted into the indolines (6) and (7), which were treated with cyanogen bromide to give selectively the 5-bromo-1-cyano-1,2,3,4,5,6-hexahydro-1-benzazocines (10) and (11). The bromides (10) and (11) were transformed into 1-cyano-1,3,4,6-tetrahydro-1-benzazocin-5(2H)-ones (13) and (14), which underwent a transannular reaction to yield the 2,3-dihydro-1H-pyrrolo[1,2-a]indoles (4) and (5).