Oxidation with hydrogen peroxide was examined with 2-(2-pyridyl)-3-phenyl-4 (3H)-quinazolinone (I
a) and its derivatives with a methyl group in 3-position (I
b), 5-position (I
c), and 6-position (I
d) of the 2-pyridyl group, in acetic acid (method A) or in trifluoroacetic acid (method B). Only N'-monoxide (II) was obtained by method A but II and N, N'-dioxide (III) were obtained by method B. (The nitrogen in 1-position of the quinazolinone ring is designated as N and that in the pyridine ring as N'). By the same reaction of 2-(4-pyridyl)-3-phenyl (or o-tolyl)-4 (3H)-quinazolinone (I
f or I
g), II was obtained by method A but III was not obtained by method B from which compounds formed by cleavage of the quinazolinone ring by further progress of oxidation, 2-nitrobenzanilide (IV
f) and 2-nitro-2'-methylbenzanilide (IV
g), were obtained, together with II. Some reactions of the N, N'-dioxides (III
c and III
d) of I
c and I
d were examined. Application of carbon disulfide or phenyl isothiocyanate to III
c in dimethylformamide resulted in deoxygenation to form N'-monoxide (II
c) of I
c. Application of phosphorus trichloride or N, N-dimethylthiocarbamoyl chloride to III
d in chloroform also resulted in deoxygenation to form N'-monoxide (II
d) of I
d. Application of N, N-diethylthiocarbamoyl chloride to II
d resulted in the formation of the anticipated rearrangement product, 2-{6-(N, N-diethylcarbamoylthio) methyl-2-pyridyl)}-3-phenyl-4 (3H)-quinazolinone (V).
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