A process for preparing (S)-(+)-10,11-dihydro-10-hydroxy-5H-dibenz/b,f/azepine-5-carboxamide or (R)-(−)-10,11-dihydro-10-hydroxy-5H-dibenz/b,f/azepine-5-carboxamide, by reduction of oxcarbazepine in the presence of a catalyst and a hydride source is disclosed. The catalyst is prepared from a combination of [RuX2(L)]2 wherein X is chlorine, bromine or iodine, and L is an aryl or aryl-aliphatic ligand, with a ligand of formula (A) or formula (B): wherein R1 is chosen from C1-6 alkoxy and C1-6 alkyl, n is a number from 0 to 5, and when n is a number from 2 to 5, R1 can be the same or different, and R2 is alkyl, substituted alkyl, aryl, substituted aryl, alkaryl or substituted alkaryl. The hydride source is either NR3R4R5 and formic acid, [R3R4R5NH][OOCH] and optionally formic acid, or [M][OOCH]x and formic acid, wherein R3, R4 and R5 are C1-6 alkyl, M is an alkali metal or alkaline earth metal and x is 1 or 2. A pH from 6.5 to 8 is maintained during the process.