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Paper | Regular issue | Vol 26, No. 9, 1987, pp.2425-2431
Published online, 1st January, 1970
DOI: 10.3987/R-1987-09-2425
1,3-Dipolar Cycloaddition of 2-Diazopropane to Coumarin. The Synthesis of Derivatives of [1]Benzopyrano[4,3-c]pyrazol-4(3H)-one and [1]Benzopyrano[3,4-c]pyrazol-4(1H)-one

Andreja Cercek, Branko Stanovnik, Anton Stimac, and Miha Tisler

*Department of Chemistry, E. Kardelj University, Murnikova 6, 61000 Ljubljana, Slovenia


1,3-Dipolar cycloaddition of 2-diazopropane (2) to unsubstituted coumarin (1) is taking place nonregiospecifically to give a mixture of cycloadducts 3 and 5. These are thermally transformed into cyclopropane derivative 6 and 4-isopropyl derivative 7, respectively. In the presence of potassium hydroxide or 2 substituted pyrazoles 8, 9 and 10 are produced. The oxidation of 3 and 5 with bromine in acetic acid gives tricyclic systems 15 and 16.