Oxalyl chloride → 4-[1-(Trifluoroacetyl)piperidin-4-yl)benzoyl chloride

To a flask containing A1Cl3 (534 mg, 4.0 mmol) under an N2 atmosphere was added anhydrous CH2Cl2 (0.1 M), and the drop wise addition of oxalyl chloride (523 μL, 6.0 mmol) over a 20 min period at 15° C. Next, a solution of 2,2,2-trifluoro-1-(4-phenylpiperidin-1-yl)ethanone (17) (2.0 mmol) in anhydrous CH2Cl2 (0.1 M) was added drop-wise to the initial solution over a 45 min period at 15° C. When the reaction was complete as judged by TLC, ice was added to the solution in addition to CaCl2 (1.70 g). The product was extract into CH2Cl2, washed with brine and dried over anhydrous Na2SO4 before concentrating under reduced pressure to yield crude 4-(1-(2,2,2-trifluoroacetyl)piperidin-4-yl)benzoyl chloride (18). (b) To a stirred solution of 18 (2.0 mmol) and DIPEA (697 μL, 4.0 mmol) in EtOAc (0.1 M) was added 10% Pd/C. The flask was then evacuated and filled with H2 gas and allowed to stir for 30 min. After which time the reaction contents were filtered and concentrated under reduced pressure to give crude product which was purified by silica gel column chromatography (hexanes:EtOAc, 2:1) to furnish 19 (320 mg, 59% (yield over 2 steps)) δH (400 MHz, CDCl3) 1.69-1.81 (m, 2H, CH2), 1.98-2.06 (m, 2H, CH2), 2.83-2.97 (m, 2H, CH2), 3.27 (td, J=12.8 and 2.4 Hz, 1H, CH), 4.13-4.21 (m, 1H, CH), 4.70-4.76 (m, 1H, CH2), 7.37 (d, J=8.4 Hz, 2H, CH), 7.85 (d, J=8.4 Hz, 2H, CH), 9.99 (s, 1H, CHO); LRMS (ES+) calcd for [C14H14F3NO2+Na] 308.09 found 308.19 [M+Na].