Acetic Acid → (+/-)-(2R,3R)-1-tert-Butyloxycarbonyl-3-(tert-butyldimethylsilanyloxy)-2-[(3-chloro-4-cyano-2-methylphenylamino)-methyl]piperidine

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A mixture of 77F (660 mg, 1.92 mmol), 4-amino-2-chloro-3-methylbenzonitrile (384 mg, 2.3 mmol, 1.2 equiv) and HOAc (165 μL, 2.88 mmol, 1.5 equiv) in 1,2-DCE (10 mL) was stirred at rt for 30 min and Na(OAc)3BH (610 mg, 2.88 mmol, 1.5 equiv) was added. The reaction was stirred at rt overnight. Another 407 mg of Na(OAc)3BH (610 mg, 1.92 mmol, 1.0 equiv) was added and stirred at rt for another 24 h. The mixture was concentrated and the residue was diluted with EtOAc (30 mL), washed with saturated sodium bicarbonate solution (2×15 mL), brine (2×15 mL), dried (MgSO4) and evaporated to give the crude product. Purification of the crude product by flash chromatography (0-50% EtOAc/hexane) yield the desired product 77G (192 mg, 20%) as a white foam: Rf (30% EtOAc/hexane) 0.37; HPLC (Phenomenex Luna 5μ C18 4.6×50 mm, linear gradient over 4 min) retention time 4.6 min (100%); MS (ES) m/z 344.1 [M+1]+; HRMS calcd for C25H41N3O3SiCl 494.2606, Found 494.2613.

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