Studies with enaminones: The reaction of enaminones with aminoheterocycles. A route to azolopyrimidines, azolopyridines and quinolines

The enaminones 1b,d,f react with 4-phenyl-3-methyl-5-pyrazoleamine 3a to yield the pyrazole derivatives 4a-c that cyclised readily on reflux in pyridine solution in presence of hydrochloric acid to yield the pyrazolo[1,5-a]pyrimidines 5a-c. Similarly 3(5)-amino-1H-triazole (3b) reacted with 1b,d,f to yield the triazolo[1,5-a]pyrimidines 5d-f. In contrast attempted condensation of the 5-tetrazoloamine (3c) with la,d,e resulted in its trimerisation and only triaroylbenzene 8a,d,e was isolated. The reaction of 1a,b,d with anthranilonitrile 9a and the reaction of 1a-c with the 2-aminocyclohexene thiophene-3-nitrile 10a afforded the cis enaminones 11a-c and 12a-c. Similarly, reaction of 1a-c with the methylanthranilate 9b and reaction of 1b,e with ethyl 2-aminocyclohexene thiophene-3-carboxylate 10b afforded the cis enaminones 11d-f and 12d,e respectively. Attempted cyclization of 11a-c into quinoline failed. Successful cyclization of 11d into the quinolinone 13 could be affected, on heating for five minutes in a domestic microwave oven at full power. The reaction of la-c,f with piperidine afforded the trans enaminones 14a-d. Similarly, trans 14e was formed from the reaction of 1b with morpholine. The coupling reaction of 1b with excess of benzene diazonium chloride afforded the formazane 16. The enaminone 2 reacted with heterocyclic amines to yield the pyridones 17,18.