2H-1,4-benzoxazin-3(4H)-one → 3,4-Dihydro-2H-1,4-benzoxazine

Participants

Reaction Steps

Into a 250 mL 3-necked round bottom flask was placed a solution of lithium aluminum hydride (3.6 g, 94.74 mmol) in tetrahydrofuran (80 mL). The mixture was stirred for 15 minutes. This was followed by the addition of a solution of 2H-benzo[b][1,4]oxazin-3(4H)-one (5.7 g, 38.22 mmol) in tetrahydrofuran (21 mL), which was added dropwise with stirring. The resulting solution was allowed to react, with stirring, overnight while the temperature was maintained at reflux in a bath of oil. The reaction progress was monitored by TLC (ethyl acetate/petroleum ether=1:1). The reaction mixture was then quenched by the adding 3.6 mL of H2O and 10.8 mL 15% NaOH. A filtration was performed. The filter cake was washed 1 time with 30 mL of tetrahydrofuran. The resulting solution was extracted two times with 100 mL of ethyl acetate and the organic layers combined and dried over Na2SO4 and concentrated by evaporation under vacuum using a rotary evaporator. This resulted in 4.8 g (79%) of 3,4-dihydro-2H-benzo[b][1,4]oxazine as red oil.

Provenance & Evidence