Parallel synthesis of 7-heteroaryl-pyrazolo[1,5-a]pyrimidine-3-carboxamides

A simple and practical four-step protocol for the parallel synthesis of 7-heteroaryl-pyrazolo1,5- $a$ ]pyrimidine-3-carboxamides was developed. The synthesis starts with transformation of commercially available 2-acetylpyridine and acetylpyrazine with $N,$ $N$ -dimethylformamide dimethylacetal into the corresponding $(E)$ -3-(dimethylamino)-1-(heteroaryl)prop-2-en-1-ones followed by cyclisation with methyl 5-amino-1 $H$ -pyrazole-4-carboxylate to give methyl 7-heteroarylpyrazolo1,5- $a$ ]pyrimidine-3-carboxylates. Hydrolysis of the ester group and subsequent amidation of the so formed carboxylic acids with 12 primary and secondary aliphatic amines furnished a library of 24 title compounds in good overall yields and purity.