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

An organocatalytic asymmetric arylmethylation/N-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-a]indoles were efficiently constructed with excellent enantioselectivity (up to >99% ee). Furthermore, the corresponding products could be easily functionalized via simple deprotonation and treatment with other electrophiles with excellent diastereoselectivities (>20:1 dr).