Stereochemistry and mechanism of the photochemical and thermal insertion of oxygen into the carbon-cobalt bond of alkyl(pyridine)cobaloximes

Oxygenation of olefins under reductive conditions. Cobalt-catalyzed selective conversion of aromatic olefins to benzylic alcohols by molecular oxygen and tetrahydroborate

“…The latter situation holds even in the photochemical oxygenation of 5-hexenylcobaloxime if the supply of oxygen is sufficient. 27 Judging from the slow rate of catalytic oxygenation, it seems likely that the rate of the reaction of generated free radical with oxygen is faster than the rate of cyclization. Thus, the present reaction proceeds primarily by the activation of hydrocarbons.…”

“…l-Phenyl-4penten-l-ol: NMR 1.82 (q, 2 ), 2.12 (q, 2 H), 4.65 (t, 1 H), 4.90-5.10 (m, 2 H), 5.60-6.30 (m, 1 H), 7.29 ppm (s, 5 H); MS (El), m/e (relative intensity) 107 (100), 79 (85), 77 (52), 120 (32), 105 (22), 51 (19), 78 (12), 104 (12), 108 (9), 55 (8), 144 (5). transl-Phenyl-l-penten-3-ol: NMR 0.94 (t, 3 ), 1.59 (q, 2 ), 4.15 (q, 1 ), 6.00-6.60 (m, 2 H), 7.25 ppm (s, 5 H); MS (El), m/e (relative intensity) 133 (100), 55 (80), 105 (58), 115 (52), 129 (51), 77 (45), 91 (43), 57 (34), 128 (33), 51 (27), M+/e, 162 (26). Experiments of deuterium incoporation were carried out in DME by the use of NaBD4 as the reductant.…”

Mn-, Fe-, and Co-Catalyzed Radical Hydrofunctionalizations of Olefins

“…Moreover, Co­(III)–alkyl complex 425 was also catalytically active and simultaneously formed PhCH 2 CH 2 CH 2 OOSiEt 3 . Analogous to Mukaiyama’s hydration proposal, insertion of the double bond into the metal hydride was suggested to form complex 426 , which would undergo homolytic cleavage of the Co–C bond. , This nascent radical would react with molecular oxygen leading to complex 416 , which would undergo transmetalation with Et 3 SiH to give product 423 and regenerate the metal hydride. The presence of radical species was confirmed by means of radical clock experiments: thus, vinylcyclopropane 427 led to the major formation of peroxide 428 under the reaction conditions, by ring opening.…”

New Developments in the Field of Vitamin B12: Reactions of the Cobalt Atom in Corrins and in Vitamin B12 Model Compounds

“…Higher alkenylcobaloximes carrying a terminal C=C bond in the cobalt-bound organic residue produce alkenyl radicals on aerobic photolysis which undergo cyclization reactions prior to the termination Alkylperoxo radicals which are formed during aerobic photolysis may also react with the cobaloxime(r1) fragments to yield isolable alkylperoxocobalt complexes [47,481. The quantum yields in typical photolysis reactions of alkylcobaloximes and -cobalamins have been determined" 6,491.…”