Condensation of triformylmethane with heteroaromatic amines, including nucleic acid bases. A novel example of ring-chain tautomerism

Abstract

Treatment of several heteroaromatic amines, including the nucleic acid bases cytosine and adenine, with triformylmethane in pyridine at 70°C afforded 1:1 condensation products (2-11) that were characterized by 1H and 13C NMR spectroscopy. All the compounds were assigned as N-substituted aminomethylenemalonaldehydes, strongly preferring the amino/keto form over the imino/enol tautomer. With cytosine and 1-methylcytosine, unequivocal evidence for ring-chain tautomerism was additionally obtained: intramolecular nucleophilic attack of cytosine N3 to one of the carbonyl carbons results in reversible cyclization to a 4-hydroxy-4H-pyrimido[1,6-a]pyrimidin-6(7H)-one derivative (9b, 10b). In dry methanol the corresponding O-methyl ether (12) was obtained. © Acta Chemica Scandinavica 1996.