Exploiting the Dual Reactivity of o-Isocyanobenzamide: Three-Component Synthesis of 4-Imino-4H-3,1-benzoxazines

A multicomponent synthesis of 4-imino-4H-3,1-benzoxazines I [R1 = H, MeO; R2 = n-Bu, PhCH2, PhCH2CH2, (S)-PhCH2CH(CO2Me), etc.; R3 = H, Me2CH, cyclohexyl, n-hexyl; R4 = H, R5 = n-Bu, MeO2CCH2CH2, PhCH2, 9-fluorenylmethyl; R4 = R5 = Me; R4R5N = morpholino] is developed. Heating a toluene soln. of an aldehyde R3CHO, an amine R4R5NH, and an isonitrile II in the presence of a stoichiometric amt. of ammonium chloride at 60 DegC for 12 h produces the benzoxazines I in good to excellent yields. [on SciFinder (R)]