Highly efficient preparation of R-1-methyl-tetrahydroisoquinoline using chiral Ru(II)-catalyst

A highly efficient route for R-1-methyl-tetrahydroisoquinoline preparation comprising Bischler–Napieralski condensation with enantioselective reduction according to the Noyori protocol for cyclic imine intermediate reduction was experimentally explored. The influence of reaction parameters on the activity and selectivity was evaluated. The enhancement of Ru-asymmetric catalyst efficiency (catalyst re-use) was tested—only a small drop of enantioselectivity in consecutive reduction cycles was found.