CONDENSED AS-TRIAZINE .2. SYNTHESIS OF 7-PHENYLDIHYDRO-[2,3-E]-AS-TRIAZINES AND TETRAHYDROPYRAZINO-[2,3-E]-AS-TRIAZINES

Certain derivatives of dihydro- and tetrahydropyrazino[2,3-e]-as-triaz ines were prepared by ring closure of 5,6-diamino-as-triazines with ph enylglyoxal in methanol. These 4-azapteridines experience an addition of the alcohol at C(7), and N(8) underwent an unusual methylation unde r acidic conditions affording the 7-methoxy-8-methyl-6-phenyldihydropy razino derivative. Regioselective control by the aldehyde-binding reag ent, sodium hydrogen sulfite and sodium sulfite, tends to direct the p henyl group to the C(7). Hinsberg reaction of 5,6-diamino-as-triazines with phenacyl bromide proceeded in regiospecific fashion to give the E-form Schiff bases which then isomerize to the corresponding enamines .