Reactions of pyrazolo(1,5-a)pyrimidine derivatives with nucleophiles. I. Nucleophilic addition to 6,7-dicarbethoxypyrazolo(1,5-a)-pyrimidine-3-carbonitrile in the presence of boron trifluoride etherate.

Abstract

Nucleophilic additions of phenol analogs, indoles, and enamines of cyclohexanone to 6, 7-dicarbethoxypyrazolo [1, 5-α] pyrimidine-3-carbonitrile (1) in the presence of boron trifluoride etherate are described. For example, though phenol or o-cresol (having no substituent at the para-position) reacted with 1 to give cyclohexadienylidene derivatives (3, 4), p-cresol or p-methoxyphenol gave the spiro {benzofuran-3 (2H), 7'(4'H)-pyrazolo-[1, 5-α] pyrimidine} compounds (6, 7) upon reaction with 1. Indoles reacted with 1 to give the 7-indolyl derivatives (11, 12). When 1 was treated with enamines of cyclohexanone in the presence of a slight excess of boron trifluoride etherate, 7-(2-amino-1-cyclohexenyl) pyrazolo [1, 5-α] pyrimidines (13, 14) were obtained as their boron trifluoride complexes in good yields.