Asymmetric synthesis of cyclopenta[b]indoles via organocatalytic formal (3 + 2) cyclization of β-keto ester with azonaphthalene

Enantioselective formal (3 + 2) cyclization of cyclic β-keto esters with azonaphthalenes to synthesize cyclopenta[ b ]indoles in good yields with high diastereo- and enantioselectivity is established by using guanidine-amides as catalysts under mild reaction conditions.