Asymmetric synthesis of (S)-norlaudanosine and (S)-tetrahydrohomopapaverine by catalytic asymmetric hydrogenation with chiral diphosphine-iridium(I)-phthalimide complex catalysts

Optically active 1,2,3,4-tetrahydroisoquinoline alkaloids, (S)-norlaudanosine and (S)-tetrahydrohomopapaverine, were prepared by catalytic asymmetric hydrogenation of 1-substituted 3,4-dihydro-6,7-dimethoxyisoquinolines with 1 mol % of an iridium(I) complex of (2S,4S)-BCPM or (S)-BINAP in the presence of a phthalimide. Enantioselectivities of up to 88% ee were attained.