To 7-hydroxy-2-(trifluoromethyl)-6,11-dihydro-5H-pyrido[2,3-b][1,5]benzodiazepin-5-one (113 g, 0.38 mol) in THF (1.7 L) at 0° C. was added BH3 (1 M/THF, 1.5 L, 1.5 mol). After gas evolution subsided, the reaction was heated at 40° C. for 1 h. The reaction mixture was cooled to 0° C. and poured slowly into methanol. The resulting solution was partially concentrated, diluted with ethyl acetate, washed with 1 N HCl, saturated NaHCO3 and brine, dried over MgSO4, filtered and concentrated. The residue was slurried in heptane, and the solid was collected by filtration to give the title compound as a 1:1 mixture with 2-(trifluoromethyl)-6,11-dihydro-5H-pyrido[2,3-b][1,5]benzodiazepin-10-ol.
