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c) 4-(Aminomethylene-1'-benzotriazolyl)benzooxazole 1H-benzo-triazole-1-methanol was added to a stirred 4-aminobenzooxazole (6.874 g, 51 mmol) solution in absolute ethanol (85 mL). The suspension was stirred at room temperature overnight. The solid was collected by filtration, washed with ethanol, and dried in vacuo to yield 10.681 g (79%) as an off-white solid. 1H NMR (CDCl3): 8.04 (d, J=8.4 Hz, 1H), 7.98 (s, 1H), 7.70 (d, J=8.4 Hz, 1H), 7.45 (dt, J=1.2, 6.9 Hz, 1H), 7.35 (dt, J=0.9, 6.9 Hz, 1H), 7.21 (t, J=8.4 Hz, 1H), 7.00 (dd, J=0.6, 8.4 Hz, 1H), 6.93 (d, J=8.1 Hz, 1H), 6.34 (d, J=7.2 Hz, 211), 5.85 (t, J=6.6 Hz, 1H). d) 4-Hydroxy-1-methylbenzimidazole To a stirred suspension of 4-(aminomethylene-1'-benzotriazolyl)benzooxazole (223 mg, 0.84 mmol) in absolute ethanol (10 mL) was added sodium borohydride (110 mg, 2.91 mmol) portion-wise (three portions) over 4 h period. The reaction mixture was then stirred overnight. To the reaction mixture was added 21% sodium ethoxide solution in ethanol (5 mL) and ethanol (10 mL). The mixture was stirred for two days at room temperature. The mixture was diluted with water (10 mL), neutralized to pH=7 with 2M hydrochloric acid, and extracted with methylene chloride (3*20 mL). The methylene chloride solution was washed with brine (10 mL), dried over MgSO4, and evaporated under reduced pressure to yield a dark oily residue. It was purified by column chromatography (silica gel, EtOAC:hexanes, 1:3, 1:2, then 100% EtOAc) to yield 62 mg (50%) of the product as a light brown solid. 1H NMR (CDCl3): 7.89 (s, 1H), 7.24 (t, J=8.1 Hz, 1H), 6.91 (dd, J=0.6, 8.1 Hz, 1H), 6.84 (dd, J=0.9, 7.8 Hz, 1H), 3.83 (s, 3H), 2.17 (s, 1H). |