Odedra, Arjan Lush, Shie-Fu Liu, Rai-Shung Dicobaltoctacarbonyl-Mediated Synthesis of Tricyclic 5,6-Diydropyran-2-one Derivatives via Tandem Cycloaddition Reaction between <i>cis</i>-Epoxyalkynes, a Tethered Olefin, and Carbon Monoxide Cobalt carbonyl complex Co<sub>2</sub>(CO)<sub>8</sub> implemented an intramolecular carbonylation of <i>cis</i>-epoxyalkynes to generate Co<sub>2</sub>(CO)<sub>6</sub>-stabilized γ-lactonyl allene species. For 1,1,2-trisubstituted epoxyalkynes, this Co<sub>2</sub>(CO)<sub>6</sub>-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 <i>cis</i>-epoxyalkyne and 1,1,2-trisubstituted <i>cis</i>-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 <i>cis</i>-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%). Tethered Olefin;species;epoxyalkyne;CO;tandem cycloadditions;Tandem Cycloaddition Reaction;heteroatom constituent;olefin;trisubstituted;Carbon MonoxideCobalt carbonyl;cyclopentanone ring;intramolecular carbonylation;cycloaddition pathways;cycloadduct;disubstituted 2007-01-19
    https://acs.figshare.com/articles/journal_contribution/Dicobaltoctacarbonyl_Mediated_Synthesis_of_Tricyclic_5_6_Diydropyran_2_one_Derivatives_via_Tandem_Cycloaddition_Reaction_between_i_cis_i_Epoxyalkynes_a_Tethered_Olefin_and_Carbon_Monoxide/3032230
10.1021/jo0620617.s002