REACTION OF 5-AMINO-1-PHENYLPYRAZOLE-4-CARBONITRILES WITH DIMETHYL ACETYLENEDICARBOXYLATE - SYNTHESIS AND STRUCTURAL DETERMINATION OF TRIMETHYL 1H-PYRAZOLO[3,4-3]INDOLIZINE-5,5A,6-TRICARBOXYLATE DERIVATIVES

The reaction of 5-amino-1-phenylpyrazole-4-carbonitriles 1a-c with dim ethyl acetylenedicarboxylate in the presence of potassium carbonate in dimethyl sulfoxide gave trimethyl 1H-pyrazolo[3,4-e]indolizine-5,5a,6 -tricarboxylate derivatives 3a-c from the basic solution. The products were formed by a double Michael reaction of 1 with dimethyl acetylene dicarboxylate followed by cyclization to the cyano group. The structur e of product 3a was established by X-ray crystallography.