b
Department of Chemistry, University of California at Berkeley, Berkeley, California 94720-1460, USA
› Author AffiliationsThis work benefited from pecuniary support by the University of California at Berkeley (K.P.C.V.). We are grateful to the National Science Foundation (CHF-1764328 to K.N.H.) for financial support. Calculations were performed on the Hoffman2 cluster at the University of California, Los Angeles, and the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by the National Science Foundation (OCI-1053575).
Congratulations to Professor Sarah Reisman at the California Institute of Technology for having been chosen as the first recipient of the Dr. Margaret Faul Award for Women in Chemistry
Abstract
The mechanisms by which the complexes CpCoL2 (Cp = C5H5; L = CO or CH2=CH2) mediate the cycloisomerizations of α,δ,ω-enynenes containing allylic ether linkages are probed by DFT methods. The outcomes corroborate experimental results and provide energetic and structural details of the trajectories leading to 3-(oxacyclopentyl or cycloalkyl)furans via the intermediacy of isolable CpCo-η4-dienes. They comprise initial stereoselective complexation of one of the double bonds and the triple bond, rate-determining oxidative coupling to a triplet 16e cobalta-2-cyclopentene, and terminal double bond docking, followed by stereocontrolled insertion to assemble intermediate cis- and trans-fused triplet cobalta-4-cycloheptenes. A common indicator of the energetic facility of the latter is the extent of parallel alignment of the alkene moiety and its target Co–Cα bond. The cobalta-4-cycloheptenes transform further by β-hydride elimination–reductive elimination to furnish CpCo-η4-dienes, which are sufficiently kinetically protected to allow for their experimental observation. The cascade continues through cobalt-mediated hydride shifts and dissociation of the aromatic furan ring. The findings in silico with respect to the stereo-, regio-, and chemoselectivity are in consonance with those obtained in vitro.
11g
Sen A,
Kang M.
In
Late Transition Metal Polymerization Catalysis
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Rieger B,
Saunders Baugh L,
Kacker S,
Striegler S.
Wiley-VCH; Weinheim: 2003: 307
