Pteridine studies. Part 46. 2-Alkylpteridin-4-ones from 2-aminopyrazine-3-carboxamide and its derivatives

Abstract

2-Aminopyrazine-3-carboxamide (1a) and its 5-bromo-derivative (1b) were converted, variously, into pteridin-4-one (2a) and its 2-methyl-, 2-trifluoromethyl-, 2-phenyl-, 6-bromo-2-methyl-, 6-bromo-2-phenyl-, and 6-ethoxy-(and 6-butoxy-)-2-trifluoromethyl-derivatives; also into 4-mercapto-2-trifluoromethylpteridine. The following methods were compared and evaluated: heating with ortho esters, with amides (alone or alkoxidecatalysed), with acid anhydrides, or with amidines; also formation of a 2,N-acyl derivative prior to ring -closure with aqueous alkali. ¹H N.m.r. and i.r. spectra were measured and discussed.