Chemistry of Diazafulvenium Methides in the Synthesis of Functionalized Pyrazoles

• Author(s): Melo, Teresa M. V. D. Pinho e ; Nunes, Cláudio M. ; Soares, Maria I. L. ; Paixão, José A. ; Beja, Ana Matos ; Silva, Manuela Ramos
• Date: 2007
• Persistent ID: http://hdl.handle.net/10316/10634
• Origin: Estudo Geral - Universidade de Coimbra
• Document Type: Article
• Language: English

Description

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 [8π + 2π] 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. http://dx.doi.org/10.1021/jo070265x