1,3-Dipolar cycloaddition of 2-diazopropane to 2-methyl-6-phenylpyridazin- 3(2H)-one. The formation of pyrazolo/3,4-D/pyridazine derivatives

Abstract

In a regiospecific 1,3-dipolar cycloaddition of 2- diazopropane to 2-itiethyl-6-phenylpyridazin-3(2H)- one the primary cycloadduct and rearranged NH,NH- dihydro cycloadduct were isolated. They were transformed, dependent on the reaction conditions into 1,2-di- azepine derivative, 4-isopropyl substituted pyridazine derivative, diazabicyclo/4.l.0/heptenone derivative and pyrazolo/3,4-d/pyridazine derivative. 1,5- Sigmatropic rearrangements were observed, when was heated in PPA or concentrated sulphuric acid to give pyrazolo/3,4-d/pyridazine derivatives 0 and 1 , and a pyrazole derivative 3 .