title: Mechanistic origin of chemo- and regioselectivity of nickel-catalyzed [3 + 2 + 2] cyclization reaction.
abstract: A density functional theory (DFT) study was performed to elucidate the mechanism of the Ni-catalyzed [3 + 2 + 2] cyclization reaction of cyclopropylideneacetate with two alkynes. A systematic search showed that the nature of the alkynes determines the choice between two reaction pathways and hence the regioselectivity. Strongly electron-deficient acetylenes preferentially afford 2,5-disubstituted products via nickelacyclopentadienes generated by [2 + 2] cocyclization, whereas normal alkynes afford 3,4- or 3,5-products via an unprecedented pathway involving a [3 + 2] nickelacycle intermediate.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Komagawa
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.forename: Keiji
authors.initials: K
authors.lastname: Morokuma
authors.forename: Shinichi
authors.initials: S
authors.lastname: Saito
authors.forename: Masanobu
authors.initials: M
authors.lastname: Uchiyama
mesh_terms: D000085:Acetates / Q000737:chemistry*; D000480:Alkynes / Q000737:chemistry*; D003521:Cyclopropanes / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000085:Acetates; D000480:Alkynes; D003521:Cyclopropanes; D009532:Nickel