Stereoselective hydrogenation of a ketone
The present invention relates to a method comprising reducing a ketone of formula I: with an enantioselective hydrogenating agent to form substantially enantiomerically pure alcohol of formula II: where R—R 4 and m are as defined herein. The method of the present invention is useful for making CCR2 modulators as wells as precursors CCR2 modulators.
1. A method comprising reducing a ketone of the following formula:
with an enantioselective ruthenium phosphine hydrogenating agent to form a substantially enantiomerically pure alcohol having the following formula:
wherein R 1 is Cbz or BOC.
2. The method of claim 1 wherein the ruthenium phosphine hydrogenating agent is
and the reduced compound has the following formula:
or a ditosylate salt thereof.
3. The method of claim 2 wherein the reduced compound or ditosylate salt thereof is further reacted with a protic acid to form (1S)-2-(6-chloro-1,2-dihydro-1′H-spiro[indole-3,4′-piperidin]-1′-yl)-1-(4-piperidinyl)ethanol.
4. The method of claim 3 wherein the (1S)-2-(6-chloro-1,2-dihydro-1′H-spiro[indole-3,4′-piperidin]-1′-yl)-1-(4-piperidinyl)ethanol is reacted with pentafluorophenyl (2E)-3-(3,5-difluorophenyl)-2-propenoate under such conditions to form (1S)-2-(6-chloro-1,2-dihydro-4H-spiro[indole-3,4′-piperidin]-1′-yl)-1-{1-[(2E)-3-(3,5-difluorophenyl)-2-propenoyl]-4-piperidinyl}ethanol.