Synthesis of substituted pyrazolo[3,4-d]pyrimidines by reactions of 5-amino-1-phenyl-1H-pyrazole derivatives with N-substituted isatins

[Figure not available: see fulltext.] The reaction of N-substituted isatins with 5-amino-1-phenyl-1H-pyrazole-4-carboxamide in refluxing methanol in the presence of excess sodium methoxide led to cyclocondensation with the formation of 1-R-1'-phenyl-1',7'-dihydrospiro[indole-3,6'-pyrazolo[3,4-d]pyrimidine]-2,4'(1H,5'H)-diones. Analogous reaction with 5-amino-1-phenyl-1H-pyrazole-4-carbonitrile was a cascade process that involved the formation of 1-R-4'-(methoxy)-1'-phenyl-1',7'-dihydrospiro[indole-3,6'-pyrazolo[3,4-d]pyrimidine]-2(1H)-ones as intermediates and led to N-R-2-[4-(methoxy)-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-6-yl]anilines. © 2016, Springer Science+Business Media New York