The [2 + 1] and [4 + 3] cyclization reactions of fulvenes with Fischer carbene complexes: new access to annulated cyclopentanones.
Pentafulvenes are regioselectively cyclopropanated with group 6 Fischer carbene complexes leading to the homofulvene ring with complete endo selectivity. The homofulvene adducts undergo in turn a further cyclopropanation with ethyl diazoacetate or cyclopentannulation with a Fischer alkenyl carbene complex to provide substituted cyclopentanones after ozonolysis of the exocyclic carbon=carbon double bond. Fischer alkynyl carbene complexes also produce the corresponding alkynyl homofulvenes, albeit the exo stereoisomer is in this case exclusively or preferentially formed. Under moderate CO pressure, tungsten alkynyl carbene complexes cycloadd to pentafulvenes in a [4 + 3] fashion, giving rise to bicyclo[3.2.1]octadien-2-ones.
Barluenga
José
J
Instituto Universitario de Química Organometálica "Enrique Moles", Unidad Asociada al CSIC, Universidad de Oviedo, Julian Clavería 8, 33071-Oviedo, Spain. barluenga@sauron.qumica.uniovi.es
Martínez
Silvia
S
Suárez-Sobrino
Angel L
AL
Tomás
Miguel
M