Optically active pheniramine by enantioselective hydrogenation of unsaturated amines, esters and acids using Ru(II)-complexes with BINAP as catalytic precursors

Pheniramine (3a) was prepared through enantioselective hydrogenation of various precursor compounds catalyzed by Ru(II)/BINAP complexes, In the case of N,N-dialkyl-3-phenyl-3-(2-pyridyl)allylamines (1 and 2) only the (Z)-isomer shows a satisfactory reactivity; moreover, the chemoselectivity is affected by the hydrogenolysis of the alkylamino group of the substrate. The enantioselectivity did not exceed 50%. 3-Phenyl-3-(2-pyridyl)acrylic acids (9 and 10) and their ethyl esters (5 and 6) gave good chemical yields only at reaction temperature greater than or equal to 50 degrees C; also in this case poor enantioselectivities (up to 35%) were achieved.