Cyclobutanone → Tert-butyl 4-cyclobutyl-1,4-diazepane-1-carboxylate

Participants

Reaction Steps

A 3-L, 3-necked, round-bottomed flask under a positive pressure of nitrogen was equipped with a mechanical stirrer and charged with tert-butylhomopiperazine-1-carboxylate (1-BOC-homopiperazine) (73.0 g, 365.0 mmol) and anhydrous dichloroethane (800 mL). To this stirred solution was added cyclobutanone (25.5 g, 363.8 mmol). The pale yellow reaction was stirred at rt for 1 h, following which, sodium triacetoxyborohydride (92.5 g, 436.3 mmol) was added portion-wise over 1 h. The reaction mixture was stirred for 48 h. 1 N NaOH(aq) (225 mL) was added to the reaction mixture and stirred for 1 h. The phases were separated and the aqueous layer was extracted with dichloroethane (2×100 mL). The organic layers were pooled, washed with satd. aq. NaCl (1×250 mL), dried over anhydrous Na2SO4 and filtered. The solvent was removed by rotary evaporation under reduced pressure to afford the crude product as pale yellow semi-solid (92.4 g, 98%). 1H-NMR (400 MHz, CDCl3) δ ppm: 3.59-3.40 (m, 4H), 2.98-2.84 (m, 1H), 2.59-2.43 (m, 4H), 2.12-2.03 (m, 2H), 2.00-1.83 (m, 4H), 1.76-1.55 (m, 2H), 1.51-1.41 (s, 9H). MS m/z (ESI+): 255.2 (M+H+).

Provenance & Evidence