Dichloromethane → 1-(Benzo-2,1,3-thiadiazole-5-ylcarbonyl)piperidine

Trimethylaluninum (2M in toluene; 3.0 mL, 6.0 mmol) was diluted into 30 mL dichloromethane to which piperidine (0.55 g, 6.5 mmol) and methyl benzo-2,1,3-thiadiazole-5-carboxylate (1.16 g, 6.00 mmol) were added. The reaction was stirred at room temperature for 2 hours and concentrated to one-half the volume by rotary evaporation. Dry toluene (25 mL) was added and the reaction solution was heated to 80° C. for 1 hour. Additional piperidine (about 0.2 g) was added and the temperature was increased to 100° C. for 1 hour. The solution was allowed to cool to room temperature and stirred overnight, at which time it was quenched with 10% citric acid and hydrochloric acid. The solution was diluted with ethyl acetate and sequentially washed with 10% citric acid, saturated sodium hydrogen phosphate and saturated sodium chloride, and subsequently dried over anhydrous sodium sulfate. The solution was concentrated onto silica and product was eluted with hexane/ethyl acetate (3:1). Purification by distillation in a kugelrohr at 180° C. and 0.5 mmHg yielded 1-(benzo-2,1,3-thiadiazole-5-ylcarbonyl)piperidine, 1 (1.29 g, 87%) as a pale yellow oil. IR: 2920, 2855, 1633, 1478, 1439, 1280, 1223, 1001, 816, and 748 cm−1. 1H NMR (500 MHz): δ8.06 (1H, d, J=9.1 Hz); 8.02 (1H, s); 7.63 (1H, t, J=9.0 and 1.5 Hz); 3.77 (2H, br s); 3.40 (2H, br s); 1.72 (4H, br s); and 1.57 ppm (2H, br s).