A novel photochemical vinylcyclopropane rearrangement yielding 6,7-dihydro-5H-benzocycloheptene derivatives
[reaction: see text] 1-Substituted 1-(2,2-diphenylvinyl)cyclopropanes with electron-accepting groups at C1 undergo a novel rearrangement to benzocycloheptenes on triplet-sensitized irradiation. In some instances competition between rearrangement to cyclopentenes and formation of cycloheptenes takes place. When electron-acceptor groups are not present at C1, conventional ring opening to cyclopentenes occurs exclusively. A mechanism involving intramolecular SET from the diphenylvinyl unit to the electron-acceptor group is proposed for this novel photoreaction.
Armesto
D
Departamento de Quimica Organica I, Facultad de Ciencias Quimicas, Universidad Complutense, Madrid, Spain. darmesto@eucmos.sim.ucm.es
Ramos
A
Mayoral
EP
Ortiz
MJ
Agarrabeitia
AR