N-Oxidation of 4-alkylquinazoline (IX), [-R=-Me (IXa), -Et (IXb)], and 4-phenyl-quinazoline (X) with monoperphthalic acid were examined. In the case of the reaction of IX, 4 (3H)-quinazolinone (II) as a main product and the corresponding 1-oxide, [-R=-Me (XIa), -Et (XIb)] and 3-oxide [-R=-Me (XIIa), -Et (XIIb)] as byproducts were obtained. It may be concluded that in N-oxidation of IX monoperphthalic acid acts as nucleophilic reagent for 4-position's carbon atom rather than electrophilic one for ring nitrogen atom so that yields of the corresponding 1-oxide and 3-oxide are very poor. Accordingly it is unable to discuss steric effect of methyl and ethyl group at 4-position for N3-oxidation. In that of X, 4-phenylquinazoline 1-oxide (XVI) and 2-aminobenzophenone (XVII) were obtained. It may be considered that formation of XVII has been originated from 4-phenylquinazoline 3-oxide (XVIII) as an intermediate. Following representative reactions were also carried out on XIa. (a) Reissert reaction. (b) Reaction by use of Tosyl chloride and alkali. (c) Grignard reaction. Reaction (a) and (b) afforded 4-methyl-2-quinazolinecarbonitrile (XX) and 2-chloro-4-methylquinazoline (XXI), respectively. Reaction (c) with methylmagnesium iodide and with ethylmagnesium bromide gave 2, 4-dimethylquinazoline 1-oxide (XXVI) and 2-ethyl-4-methylquinazoline 1-oxide (XXVII), respectively. Reaction (c) with phenyl-magnesium bromide gave 2-phenyl-4-methylquinazoline (XXVIII) and its 1-oxide (XXIX).
