SYNTHESIS OF BIOISOSTERIC PYRAZOLO[1,5-ALPHA]PYRIMIDINES AS LEISHMANICIDES

Cyclocondensation of 5-aminopyrazoles (1a-d) with ambident electrophil es such as beta-ketoesters (2, 4, 11) and beta-diketones (6) in acetic acid has provided functionalised pyrazolo[1,5-a]pyrimidines (3, 5, 7, 12). Similar condensation using diethyl ethoxymethylene malonate (9a) and ethyl ethoxymethylenecyanoacetate (9b) as ambiphilic electrophile s produced 10a-f in fairly good yield. Properly functionalised pyrazol o[1,5-a]pyrimidines (7b,c) have been further cyclized to 8a, b in boil ing formamide. Ketene dithioacetals (13, 15, 17) have been also employ ed as an ambident electrophiles in the condensation cyclization reacti on with 1a-d and products isolated have been characterized as 14a-f, 1 6a-fand 18a-d.