N-Vinyl- and C-vinylpyrroles from azafulvenium methides. flash vacuum pyrolysis route to 5-Oxo-5H-pyrrolizines and 1-azabenzo[f]azulenes.
1-Azafulvenium methides, generated from pyrrolo[1,2-c]thiazole-2,2-dioxides' thermal extrusion of sulfur dioxide, led to the synthesis of functionalized pyrroles. The intramolecular trapping of these transient 8pi 1,7-dipoles in pericyclic reactions, namely sigmatropic [1,8]H shifts and 1,7-electrocyclization, allowed the synthesis of N-vinylpyrroles and C-vinylpyrroles which, under flash vacuum pyrolysis conditions, are converted into 5-oxo-5H-pyrrolizines or 4-oxo-1,4-dihydro-1-aza-benzo[f]azulenes, respectively. These heterocycles can also be obtained directly from FVP of pyrrolo[1,2-c]thiazole 2,2-dioxides. The synthesis and X-ray structure of a new 6-oxocyclopenta[b]pyrrole derivative is also reported.
Pinho e Melo
Teresa M V D
TM
Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal. tmelo@ci.uc.pt
Soares
Maria I L
MI
Gonsalves
António M d'A Rocha
AM
Paixão
José A
JA
Beja
Ana Matos
AM
Silva
Manuela Ramos
MR