MICRO WAVE-ASSISTED SELECTIVE SYNTHESIS OF 2H-INDAZOLES VIA DOUBLE SONOGASHIRA COUPLING OF 3,4-DIIODO-PYRAZOLES AND BERGMAN-MASAMUNE CYCLOAROMA-TIZATION

摘要

The microwave-assisted double Sonogashira coupling of 3,4-diiodo-1-trityl and 1-phenylpyrazole with terminal acetylene took only three minutes. Dialkynylpyrazoles, the coupling products, were heated at 240 °C in the presence of 1,4-cyclohexadiene to obtain 2H-2-trityl and 2-phenylindazoles, respectively. This synthetic route to 2H-indazole, which was achieved via cyclization to form the 6-membered ring of dialkynylpyrazole, is a novel procedure.