Cobalt-mediated intermolecular radical additions to carbon-to-carbon double bonds leading to new functionalised alkenes

Alkyl radicals generated by photolytic homolysis of cobalt salophen reagents, e.g.(6) and (15), are shown to add to activated carbon-to-carbon double bonds, i.e. ethyl acrylate, methyl vinyl ketone, acrylonitrile, and styrene, producing preparatively useful yields of new alkene products, viz.(9), (10), (12) and (14)[from (6)], and (16)[from (15)]. The reactions proceed via radical (Michael) additions, followed by ‘dehydrocobaltation’ from the presumed organocobalt intermediates (2)(Scheme 4). By use of this chemistry, in combination with the Schrauzer ‘hydrocobaltation’ reaction of alkenes, a new method for the cross-coupling reactions between two alkenes, leading to new functionalised alkenes, e.g.(24), (25), (26), (27), (28), and (29), is developed [Equation (2)].

[1]  B. Giese,et al.  On the Formation of “Free Radicals” from Alkylcobalt Complexes , 1989 .

[2]  B. Branchaud,et al.  A novel strategy for the synthesis of ammonium 3-deoxy-D-manno-2-octulosonate (ammonium KDO) from lower monosaccharides. C-C bond construction of C6 of D-mannose via cobaloxime-mediated radical alkyl-alkenyl cross coupling , 1989 .

[3]  B. Giese,et al.  Syntheses and Reactions of Glycosylcobaloximes , 1988 .

[4]  L. Walder,et al.  Vitamin B12-mediated electrochemical reactions in the synthesis of natural products , 1987 .

[5]  G. E. Keck,et al.  A New "One-Electron" Carbon-Carbon Bond Forming Reaction: Separation of the Chain Propagation Steps in Free Radical Allylation. , 1986 .

[6]  B. Giese.  Synthesen mit Radikalen – C‐C‐Verknüpfungen via Organozinn‐ und ‐quecksilberverbindungen , 1985 .

[7]  B. Giese.  Syntheses with Radicals—C ? C Bond Formation via Organotin and Organomercury Compounds [New Synthetic Methods (52)] , 1985 .

[8]  D. Barton,et al.  Carbethoxyallylation using radical chemistry , 1984 .

[9]  B. Giese.  Formation of CC Bonds by Addition of Free Radicals to Alkenes , 1983 .

[10]  J. Hooz,et al.  A Method for the Regiospecific Synthesis of Unsymmetric Acyclic Enones via Enol Boranes , 1981 .

[11]  R. M. Gerkin,et al.  Reaction of epoxides with tri-n-butylcarbethoxymethylidenephosphorane. Formation of unsaturated esters , 1967 .

[12]  G. Schrauzer,et al.  Cobalamin Model Compounds. Preparation and Reactions of Substituted Alkyl- and Alkenylcobaloximes and Biochemical Implications , 1967 .

[13]  D. Cheshire,et al.  A new synthetic route to (±)-forskolin , 1989 .

[14]  B. Branchaud,et al.  Effect of a remote ligand substituent on premature β-H elimination in a cobaloxime-mediated radical alkyl-alkenyl cross coupling , 1988 .

[15]  B. Branchaud,et al.  Alkyl-alkenyl cross coupling via alkyl cobaloxime radical chemistry.An alkyl equivalent to the heck reaction compatible with common organic functional groups , 1988 .

[16]  J. Hutchinson,et al.  Dichotomous reactivity in stannane and cobalt mediated radical cyclisations , 1987 .

[17]  G. E. Keck,et al.  One electron C-C bond forming reactions via allylstannanes: scope and limitations , 1985 .