Asymmetric Desymmetrization of para ‐Quinamines via (3+2) Cycloaddition With 1,3,5‐Triazinanes

Asymmetric catalytic synthesis of a number of hydrobenzoimidazoles was achieved from para-quinamines and 1,3,5-triazinane. A chiral rare-earth metal catalyst of N,N'-dioxide was disclosed to be efficient under mild reaction condition, benefiting the formal (3+2) cycloaddition in good yield and enantioselectivity with exclusively cis-diastereoselectivity. The enantioselectivity-determining step is an intramolecular aza-Michael reaction, and the optimized catalyst is absent from the existing database of the related asymmetric Michael reaction. The results lead to a useful supplement to the related database for prediction.