Boron tribromide → HCID 21910326, compound

Participants

Reaction Steps

A solution of 2,8-dimethoxy-5H-dibenz[b,f] azepine (8) (1.0 g; 3.95 mmol) in warm CH2Cl2 (23.5 mL, dried over molecular sieve 4A), maintained under a CaSO4 drying tube, was cooled in an ice bath (8 separates as a fine suspension) and treated with BBr3 (1.85 mL; 19.6 mmol; 5 eq). The mixture immediately turned blue and became homogeneous. The ice bath was removed after 5 minutes and the reaction was stirred at ambient temperature for 3.5 hours. The mixture was carefully blended into H2O (350 mL) (HBr evolution!) and extracted four times with EtOAc (100 mL each). The combined EtOAc layers were washed with brine (100 mL) then transferred to a 3-neck round bottom flask and rapidly mechanically stirred with a solution of NaIO4 (3.0 g) in H2O (100 mL) for 15 minutes. During this time the reaction turned dark red-brown and a solid separated. The mixture was filtered and the collected solids were washed liberally with H2O and EtOAc then dried to give the title compound (1) (0.76 g; 86%). A portion was recrystallized from boiling DMF then vacuum dried at 130° C. to afford the analytical sample as fine black whiskers with mp=239-41° C. (dec.): IR (KBr) cm-1 3475, 1600, 1555, 1538, 1453, 1340, 1270, 1230, 1115, 885, 895, 795; 1H NMR (DMSO-d6) δ6.85 (br. s, 2H), 6.95-7.08 (m, 4H), 6.66 (br. d, J=7.5 Hz, 2H); mass spectrum, m/e 223, 195 (base), 178, 166; λmax =456 nm (7,270) (pH=4.98; 0.1 M acetate) λmax =574 nm (70,250) (pH=7.8; 0.1 M borate), pKa =6.34.

Provenance & Evidence