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