Cycloadditions with 1-phenyl-5-vinylpyrazole

Abstract

1-Phenyl-5-vinylpyrazole reacts with dimethylacetylenedicarboxylate (DMAD), N-phenylmaleimide (NPMI), tetracyanoethylene (TCNE), 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), and diethyl azodicarboxylate (DEAZD) to afford 1:1 adducts through Diels–Alder cycloadditions. Ene reaction products were not detected in these reactions. Treatment of the dihydroindazole from the reaction with DMAD, gave the corresponding indazole. In the reactions with methyl propiolate (MP) a 1:2 adduct was obtained from a double Diels–Alder reaction followed by extrusion of ethylene.