title: Dicobaltoctacarbonyl-mediated synthesis of tricyclic 5,6-diydropyran-2-one derivatives via tandem cycloaddition reaction between cis-epoxyalkynes, a tethered olefin, and carbon monoxide.
abstract: Cobalt carbonyl complex Co2(CO)8 implemented an intramolecular carbonylation of cis-epoxyalkynes to generate Co2(CO)6-stabilized gamma-lactonyl allene species. For 1,1,2-trisubstituted epoxyalkynes, this Co2(CO)6-allene species reacted with a tethered olefin to give [2+2]-cycloadducts, and with CO and a tethered olefin to produce [2+2+1]-cycloadducts. These resulting cycloadducts have a 5,6-diydropyran-2-one core fused with a cyclobutane and a cyclopentanone ring, respectively. For 1,2-disubstituted cis-epoxyalkyne and 1,1,2-trisubstituted cis-epoxyalkynes bearing a heteroatom constituent, cyclization of the corresponding epoxyalkyne with a tethered alkene is invariably accompanied by incorporation of CO to produce a [2+2+1]-cycloadduct, even in the absence of CO. We have prepared various 1,1,2-trisubstituted and 1,2-disubstituted cis-epoxyalkynes to generalize such cycloaddition pathways. Attempt to use an organic promoter to perform these tandem cycloadditions was unsuccessful because of a competing Pauson-Khand reaction. Cyclization of a 1,2-disubstituted epoxyalkyne with a tethered diene was achieved successfully in one case, but the yield was low (25%).
authors.affiliation: Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC.
authors.forename: Arjan
authors.initials: A
authors.lastname: Odedra
authors.forename: Shie-Fu
authors.initials: SF
authors.lastname: Lush
authors.forename: Rai-Shung
authors.initials: RS
authors.lastname: Liu
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D000480:Alkynes / Q000737:chemistry*; D002248:Carbon Monoxide / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D003500:Cyclization; D004852:Epoxy Compounds / Q000737:chemistry*; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D000480:Alkynes; D004852:Epoxy Compounds; D009942:Organometallic Compounds; D011714:Pyrans; D003035:Cobalt; D002248:Carbon Monoxide