Chemistry of diazafulvenium methides in the synthesis of functionalized pyrazoles |
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| Authors: | Pinho e Melo Teresa M V D Nunes Cláudio M Soares Maria I L Paixão José A Beja Ana Matos Silva Manuela Ramos |
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| Affiliation: | Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal, and Department of Physics, University of Coimbra, 3004-516 Coimbra, Portugal. |
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| Abstract: | The chemistry of diazafulvenium methides generated by the thermal extrusion of sulfur dioxide from 2,2-dioxo-1H,3H-pyrazolo[1,5-c] [1,3]thiazoles is described. The diazafulvenium methides unsubstituted at C-7 participate in [8 pi + 2 pi] cycloadditions giving pyrazolo-annulated heterocycles resulting from the addition across the 1,7-position. 1-Methyl-diazafulvenium methides and 7,7-dimethyl-diazafulvenium methides undergo intramolecular sigmatropic [1,8]H shifts giving vinyl-1H-pyrazoles. |
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