An Approach to Cyclohepta[<i>b</i>]indoles through an Allenamide (4 + 3) Cycloaddition–Grignard Cyclization–Chugaev Elimination Sequence

Abstract

A strategy for synthesizing highly functionalized cyclohepta­[<i>b</i>]­indoles through a concise (4 + 3) cycloaddition–cyclization–elimination sequence is described. The cycloaddition features nitrogen-stabilized oxyallyl cations derived from epoxidations of <i>N-</i>aryl-<i>N-</i>sulfonyl-substituted allenamides, while the cyclization and elimination employed an intramolecular Grignard addition and a one-step Chugaev process, respectively