title: Chemistry of diazafulvenium methides in the synthesis of functionalized pyrazoles.
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.
authors.affiliation: Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal, and Department of Physics, University of Coimbra, 3004-516 Coimbra, Portugal.
authors.forename: Teresa M V D
authors.initials: TM
authors.lastname: Pinho e Melo
authors.forename: Cláudio M
authors.initials: CM
authors.lastname: Nunes
authors.forename: Maria I L
authors.initials: MI
authors.lastname: Soares
authors.forename: José A
authors.initials: JA
authors.lastname: Paixão
authors.forename: Ana Matos
authors.initials: AM
authors.lastname: Beja
authors.forename: Manuela Ramos
authors.initials: MR
authors.lastname: Silva
mesh_terms: D007093:Imidazoles / Q000737:chemistry*; D011720:Pyrazoles / Q000138:chemical synthesis*; D013458:Sulfur Dioxide / Q000737:chemistry; D013844:Thiazoles / Q000737:chemistry
chemical_list: D007093:Imidazoles; D011720:Pyrazoles; D013844:Thiazoles; C113487:diazafulvene; D013458:Sulfur Dioxide