反应详情

The 2(R,S)-(dioxolan2-yl)-3,4-dihydro-2H-1,4-benzoxazine employed as the starting material is prepared by reaction of 500 mg of N-benzyloxycarbonyl-2(R,S)-formyl-3,4-dihydro-2H-1,4-benzoxazine (Example 107)with 0.28 ml of ethylene glycol in 25 ml of toluene under reflux, with azeotropic removal of water, overnight in the presence of 25 mg of p-toluenesulfonic acid hydrate. After customary working up and FC of the crude product over silica gel with a 6:1 mixture of toluene and ethyl acetate, N-benzyloxycarbonyl-2(R,S)-(dioxolan2-yl)-3,4-dihydro-2H-1,4-benzoxazine is obtained (Rf- (3:1 mixture of toluene and ethyl acetate)=0.52). Subsequent hydrogenolysis analogously to Example 1r) gives 2(R,S)-(dioxolan2-yl)-3,4-dihydro-2H-1,4-benzoxazine: Rf (P)=0.74; FAB-MS: (M+H)+ =208.