REGIOSELECTIVE SYNTHESIS OF SUBSTITUTED AND FUSED PYRAZOLO[1,5-A]PYRIMIDINES AS LEISHMANICIDES

Cyclocondensation of 3,5-diaminopyrazoles (1a-d) with ketene dithioacetals 2a,b and 5 separately in acidic and basic media yields 3,4 and 6a,b. The latter on boiling with acetic anhydride affords the diacetyl derivative 7a-c. Similar reaction of 1a-d with benzocyclic ketene dithioacetals (8a,b) in acetic acid affords the angularly fused pyrazolo[1,5-a]pyrimidines (9a-h). Refluxing of 9c with acetic anhydride affords the diacetyl derivative 11. Dethiomethylation of 9d,e,h with Raney nickel in methanol yields 10d,e,h. Condensation-cyclization of 1a-d with ambident electrophiles, ethyl arylidenecyanoacetate and arylidenemalononitrile in neutral medium separately provides 12 and 15a-c with the exception of the aromatized products 17 and 14. Oxidation of 15 with DDQ affords 16 while the tetrahydro derivative 12 under similar reaction conditions remains unaffected. Attempts for condensation of 1 with malononitrile or benzyl malononitrile either in acidic or basic medium also remain unsuccessful. Some of the compounds have been screened for their leishmanicidal activity.