Synergistic Catalysis for Asymmetric [3 + 2] Cycloadditions of 2-Indolylmethanols with -Unsaturated Aldehydes.

A catalytic asymmetric [3 + 2] cycloaddition of 2-indolylmethanols with -unsaturated aldehydes was developed for the first time. This transformation was achieved by a synergistic catalytic system consisting of a palladium complex, a Brønsted acid, and a chiral secondary amine to synthesize biologically active cyclopenta[]indole derivatives with excellent diastereo- and enantioselectivities (up to >20:1 dr, up to 99% ee).

Enantioselective Construction of Dihydropyrido[1,2-]indoles via Organocatalytic Arylmethylation of 2-Enals with Inert Aryl Methane Nucleophiles.

An organocatalytic asymmetric arylmethylation/-hemiacetalization of 2-indolyl methane derivatives and 2-enals was developed. Notably, the 2-methyl of indole was readily deprotonated to produce highly reactive nucleophilic species by introducing the nitro group at the C3 position of the indole ring. A spectrum of valuable chiral dihydropyrido[1,2-]indoles were efficiently constructed with excellent enantioselectivity (up to >99% ee).