抄録
N-Alkylation of 10H-pyrido [3, 2-b]-[1, 4]-benzoxazine (I) was examined both in alkaline and neutral media. 10-Alkyl-10H-pyrido [3, 2-b]-[1, 4]-benzoxazine derivatives were easily obtained by the reaction of I with a variety of alkyl halides (methyl iodide, isobutyl bromide, dimethylaminopropyl chloride, etc.) in dimethylformamide, in the presence of sodium hydride. 10-Methyl-10H-pyrido [3, 2-b]-[1, 4]-benzoxazine (XI) was prepared by this method. Reaction of I with methyl iodide in acetone afforded the corresponding quaternary salt. 1-Methyl-1H-pyrido [3, 2-b]-[1, 4]-benzoxazine (XXIII) was obtained by the treatment of this quaternary salt with sodium carbonate solution. The compounds XI and XXIII were used as models for the amino and imino tautomers of I, and ultraviolet spectra of these model compounds were compared. The spectral data show that the amino tautomer is preferred in both cyclohexane and methanol. The selective alkylation pathways of I were discussed with some evidence and speculations.
