Chemical synthesis with metal Atoms. Cyclodimerization of norbornadiene via nickela-cyclopentane intermediates.

Formation of a Substituted Tetrahydrofuran by Formal [2 + 2 + 1] Coupling of an Oxygen Atom with Two Olefins at a Nickel Center

“…Elemental analyses were carried out by Desert Analytics (Tucson, AZ). The nickelacyclopentane 2 was prepared according to the literature method. , …”

“…Metal-mediated reactions of N 2 O with alkenes to give analogous oxametallacyclobutane complexes or free epoxides have not been reported. Recently we have demonstrated that nitrous oxide reacts with a variety of organonickel complexes via O-atom insertion into Ni−alkyl or Ni−aryl bonds to give new alkoxide or aryloxide products, examples of which are shown in eqs 1 and 2. , Since it is well-established that strained-ring olefins can be catalytically cyclodimerized or cyclotrimerized using Ni(0) complexes or atoms, , we have investigated the possibility of taking advantage of Ni(0)-based chemistry to effect the coupling of two olefins with the O atom of nitrous oxide in a novel, potentially catalytic route to tetrahydrofurans.

…”

“…In a classic study, Binger and co-workers showed that under mild conditions the strained-ring olefins 3,3-dimethylcyclopropene, methylenecyclopropane, and norbornadiene react with (bpy)Ni(cod) ( 1 ; bpy = 2,2‘-bipyridine, cod = 1,5-cyclooctadiene) to undergo cycloaddition with formation of isolable nickelacyclopentane complexes that are catalysts for cyclodimerization of the olefins . Thus, 1 reacts with norbornadiene to give, in high yield, the nickelacyclopentane 2 exclusively as the exo , trans , endo isomer (eq 3). ,

…”

“…Whereas 2 reacts with excess norbornadiene at elevated temperatures (90 °C) to reductively eliminate the exo , trans , endo -norborornadiene dimer and enter into a catalytic cycle for olefin cyclodimerization, , 3 is inert toward simple thermal reductive elimination with C−O bond formation in the presence or absence of norbornadiene. This is consistent with our general observation that thermolysis of a (bpy)Ni(OR)(R‘) complex does not result in ether elimination but, rather, β-H elimination occurs when a β-H is sterically accessible.…”