H. L. Yale, J. T. Sheehan
Apr 1, 1973
Citations
0
Influential Citations
13
Citations
Journal
Journal of Heterocyclic Chemistry
Abstract
2-Amino-3-(o-bromobenzyloxy)pyridine (1) and ethyl acetoacetate gave 9-(o-bromobenzyl-oxy)-2-methyl-4H-pyrido[1,2-α]pyrimidin-4-one (2) in 2% yield. When 1 and methyl β-amino-crotonate (3) were reacted, benzyl ether cleavage occurred and the products were 9-hydroxy-2-methyl-4H-pyrido[1,2-α]pyrimidin-4-one (4) and its ammonium salt (5). These observations led to an alternative synthesis in which 2-amino-3-pyridinol (6) and either 3 or methyl acetoacetate, (8) in diethylbenzene at 185° gave 4 in 86 and 87% yields, respectively, and the anion of 4 and o-bromobenzyl bromide gave 2 in 61% yield. Even in diethylbenzene at 185°, 1 and 8 gave only trace amounts of 2. Thus, o-bromobenzylation of the 3-hydroxyl group in 6 markedly decreased the reactivity of the amino group in 6 toward reactions with acetoacetic esters.