title: Highly chemo-, regio-, and stereoselective [3+2]-cyclization of activated and deactivated allenes with alkenyl Fischer carbene complexes: a straightforward access to alkylidenecyclopentanone derivatives.
abstract: A broad range of functionalized 5-alkylidenecyclopentene derivatives are synthesized by the rhodium(I)-catalyzed [3+2]-cyclization reaction of chromium alkenyl(methoxy)carbene complexes 1 and activated allenes. Thus, amidocyclopentenes 4a-n are readily available from N-allenylamides 2a-c, while phenoxyallene 2e gives access to phenoxycyclopentenes 6. In turn, the cyclization reaction with (alkoxycarbonyl)allenes 3 leads to (alkoxycarbonyl)methylidenecyclopentenes 7-10. In terms of selectivity, most cyclization reactions take place with complete chemo-, regio-, and diastereoselectivity. Representative cycloadducts are efficiently hydrolyzed to the corresponding 2-alkylidenecyclopentanones 11a-e without tautomerization or isomerization. Finally, a tentative reaction pathway is proposed that involves the rhodium(I) carbene complexes as the species responsible for the [3+2]-cyclization.
authors.affiliation: Instituto Universitario de Química Organometalica Enrique Moles, Unidad Asociada al CSIC, Universidad de Oviedo, Julian Clavería 8, 33071 Oviedo, Spain. barluenga@uniovi.es
authors.forename: José
authors.initials: J
authors.lastname: Barluenga
authors.forename: Rubén
authors.initials: R
authors.lastname: Vicente
authors.forename: Luis A
authors.initials: LA
authors.lastname: López
authors.forename: Miguel
authors.initials: M
authors.lastname: Tomas