Synthesis and antifungal activity of some imidazo, pyrazino and v-triazoloquinoxalines

The reaction of 6,7-diamino-1,4-diethyl-quinoxaline-1 H,4 H-2,3-dione (1) with aliphatic and aromatic carboxylic acids in the presence and absence of an acid catalyst affords 2-alkyl- and 2-aryl-5,8-diethyl-imidazo{[}4,5-g]quinoxaline-5H,8H-6,7-diones 2a-1. Cyclization of 1 with carbon disulphide in basic medium yields 2-mercapto-5,8-diethyl-imidazo{[}4,5-g]-quinoxaline-5H,8H-6,7-dione (4) which on reactions with methyl iodide and substituted benzyl halides give the S-substituted derivatives 5a-f. Condensation of 1 with 1,2-diketones yields the corresponding pyrazinoquinoxalines 6a-e. v-Triazoloquinoxaline 7 is obtained by cyclization of 1 with nitrous acid. Compounds 2a-1, 5a-f and 6a-e exhibit moderate to weak antifungal activity.