v-Triazolo[4,5-d]pyrimidines (8-azapurines). Part 24. The 3-alkyl derivatives
Abstract
4-Methylamino-1,2,3-triazole-5-carboxamide (2e) and its 3-benzyl derivative (2b) were cyclized with hydrochloric acid and triethyl orthoformate to give 3-methyl-8-azapurin-6(1H)-one (1c) and its 9-benzyl derivative (1b). The reaction mechanism is discussed. The 8-azapurinone (1c) was converted by phosphorus pentasulphide into 3-methyl-8-azapurine-6(1H)-thione (9) and an extraordinary by-product, 5-amino-1,2,3-thiadiazole-4-N-(thioformyl)carbothioamide (10). Hydrogenation of the two 8-azapurinones (1c) and (1b) gave 1,2-dihydro-3-methyl-8-azapurin-6(3H)-one (7b) and its 9-benzyl derivative (7a), respectively.
4-Methylamino-1,2,3-triazole-5-carbonitrile (12c) was converted by formamidinium acetate into 6-amino-3-methyl-8-azapurine (13a). Hydrogenation of 3-benzyl-4-methylamino-1,2,3-triazole-5-carbonitrile (12b) produced 5-aminomethyl-3-benzyl-4-methylamino-1,2,3-triazole (14a) which gave formly (14b) and acetyl, formyl (14c) derivatives when cyclization was attempted. Several Dimroth retrogressions were encountered, in which a methyl group appeared to move from the exocyclic 4-amino-group to a nitrogen atom (N-3) in the ring, in one instance displacing a 3-benzyl group. Two other unusual by-products were the highly fluorescent diacylamine, 3-benzyl-4-methylamino-5-N-formylcarboxamide (6) obtained by ring-opening of the 8-azapurinone (1b), and bis-(3-benzyl-4-methylamino-1,2,3-triazol-5-carbonyl)amine (3) from the action of sodium ethoxide on the triazole (2d).
1 H N.m.r., i.r., and mass spectra of the products are discussed. The 1H n.m.r. spectra of three triazoles showed several twinned sets of signals due to stable rotamers. There were several unusual features in the i.r. spectrum of 3-methyl-8-azapurin-6(1H)-one.