Selective Synthesis of Acenaphtho[1,2-b]indole Derivatives via Tandem Regioselective Aza-Ene Addition/N-Cyclization/SN1 Type Reaction

A concise and efficient synthesis of acenaphtho[1,2‐b]indoles with different substitution patterns from a [3+2] condensation of enaminones with acenaphthoquinone has been developed. During the first pathway, products 3 were synthesized in the presence of Et3N, while a second reaction in the presence of p‐toluenesulfonic acid leads to compounds 5 via intramolecular cyclization and highly regioselective SN1‐type reaction with alcohols under solvent‐free conditions. Both procedures give excellent yields and are highly eco‐benign, are convenient one‐pot operations, are highly regioselectivity, and use environmentally friendly solvent systems or operate under solvent‐free conditions. This method offers an alternative to regioselective construction of biologically meaningful polycyclic indoles. Ace: A concise and efficient synthesis of acenaphtho[1,2‐b]indoles with different substitution patterns from a [3+2] condensation of enaminones with acenaphthoquinone has been developed.