title: NiICatalyzes the Regioselective Cross-Coupling of Alkylzinc Halides and Propargyl Bromides to Allenes.
abstract: We describe the unprecedented formation of allenes by Ni-catalyzed cross-coupling of propargyl bromides with alkylzinc halides. The reaction regioselectivity is complementary to the previously reported formation of propargyl-coupled compounds. Experiments support the formation of NiIcomplexes as the active species and the participation of radical intermediates. Kinetic studies showed that the reaction is first order with respect to the electrophile, zero-order with respect to the nucleophile (fast transmetalation), and one-half order with respect to the metal catalyst. Mechanistic studies support a bimetallic NiI-based pathway that involves fast homolytic cleavage of the C-Br bond by an alkyl-NiIcomplex, followed by radical coordination to NiIthat determines the observed regioselectivity.
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias, Institute for Advanced Research in Chemical Sciences, IAdChem, Universidad Autónoma de Madrid, Av. Francisco Tomás y Valiente 7, Cantoblanco, 28049, Madrid, Spain.
authors.forename: Rita
authors.initials: R
authors.lastname: Soler-Yanes
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias, Institute for Advanced Research in Chemical Sciences, IAdChem, Universidad Autónoma de Madrid, Av. Francisco Tomás y Valiente 7, Cantoblanco, 28049, Madrid, Spain.
authors.forename: Iván
authors.initials: I
authors.lastname: Arribas-Álvarez
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias, Institute for Advanced Research in Chemical Sciences, IAdChem, Universidad Autónoma de Madrid, Av. Francisco Tomás y Valiente 7, Cantoblanco, 28049, Madrid, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Guisán-Ceinos
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias, Institute for Advanced Research in Chemical Sciences, IAdChem, Universidad Autónoma de Madrid, Av. Francisco Tomás y Valiente 7, Cantoblanco, 28049, Madrid, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Buñuel
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias, Institute for Advanced Research in Chemical Sciences, IAdChem, Universidad Autónoma de Madrid, Av. Francisco Tomás y Valiente 7, Cantoblanco, 28049, Madrid, Spain.
authors.forename: Diego J
authors.identifier: http://orcid.org/0000-0002-1707-6445
authors.initials: DJ
authors.lastname: Cárdenas
keywords: allenes; cross-coupling; density functional calculations; nickel; reaction mechanisms