Dj. Collins et al., REGIOSPECIFIC SYNTHESES OF THE MONOMETHYLATED 3-PHENYLDIHYDRO-1,2,4-TRIAZIN-6(1H)-ONES, Australian Journal of Chemistry, 49(4), 1996, pp. 463-468
Unambiguous syntheses of four unreported monomethylated derivatives of
3-phenyldihydro-1,2,4-triazin-6(1H)-ones, namely, the 1-methyl (2), 2
-methyl (3), 4-methyl (4) and the imidic O-methyl derivative (5), are
described. Regioselectivity was achieved for the synthesis of (2) by a
ddition of ethyl glycinate to the 1,3-dipolar nitrile imine derived fr
om N-methylbenzohydrazonoyl bromide hydrobromide (8). The key step for
the synthesis of (3) was addition of benzyl 3-methylcarbazate (14) to
ethyl N-[chloro(phenyl)methylene]glycinate (15b). The 4-methyl compou
nd (4) was prepared by cycloaddition of ethyl N-(thiobenzoyl)sarcosina
te (21) with hydrazine hydrate, and the O-methyl compound (5) was prep
ared by reaction of sodium methoxide with 6-chloro-3-phenyl-4,5-dihydr
o-1,2,4-triazine (23).