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

Okamoto, Tadashi; Oka, Shinzaburo

doi:10.1021/jo00183a020

Cited by 96 publications

(34 citation statements)

References 4 publications

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“…75 This improved reaction used the cobalt(II) porphyrin, Co(TPP), as catalyst, and Et 4 NBH 4 as reductant. The catalyst hydrates aryl-conjugated alkenes in yields of 14–98% and the reactions are run for 2–10 days.…”

Section: C-o Bondsmentioning

confidence: 99%

“…75 Moreover, isolation of the corresponding cobalt-alkyl ( 420 ) and cobalt-peroxy ( 416 ) complexes was possible and they were tested towards the formation of the hydration product; both of them afforded 1-phenylethanol in excellent yield, which suggested that these are viable reaction intermediates. Other early examples of metal-alkyl complexes were reported in the literature in which cobalt, manganese or iron catalysts bearing electron-rich ligands were used.…”

Section: Mechanistic Overviewmentioning

confidence: 99%

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

et al. 2016

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Cofactor-mimetic aerobic oxidation has conceptually merged with catalysis of syngas reactions to form a wide range of Markovnikov-selective olefin radical hydrofunctionalizations. We cover the development of the field and review contributions to reaction invention, mechanism and application to complex molecule synthesis. We also provide a mechanistic framework for understanding this compendium of radical reactions.

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Section: C-o Bondsmentioning

confidence: 99%

Section: Mechanistic Overviewmentioning

confidence: 99%

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

et al. 2016

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“…11,12,20,21) The presence of molecular oxygen has remarkably effected the reduction of 1. As the amount of oxygen bubbled into the reaction mixture is increased, the yield of 2 is further decreased even with 1200 mmol of NaBH 4 .…”

Section: )mentioning

confidence: 99%

“…[8][9][10][11][12][13][14] Herein, we report the biomimetic reduction of 1 with sodium borohydride catalyzed by metalloporphyrins in organic solvents under anaerobic and aerobic conditions.…”

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confidence: 99%

Biomimetic Reduction of Nimesulide with NaBH4 Catalyzed by Metalloporphyrins.

Chauhan

Kandadai

Kumar

2002

CHEMICAL & PHARMACEUTICAL BULLETIN

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The biomimetic reduction of anti-inflammatory drug, nimesulide (1) with sodium borohydride catalyzed by 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides [TAPFe(III)Cl] has been studied in organic solvents under anaerobic and aerobic conditions. Key words biomimetic reduction; nimesulide; metalloporhyrin; sodium borohydride; 4-aminonimesulide; 4Ј-hydroxynimesulide Nimesulide (4-nitro-2-phenoxymethanesulfonanilide) (1) is a potent nonsteroidal anti-inflammatory, analgesic and anti-pyretic agent. It inhibits cyclooxygenase-2 selectively 1,2) and reduces prostaglandin proinflammatory activity without interfering with the production of cytoprotective prostaglandins of gastric mucous membrane.3) 4-Aminonimesulide (2) (reductive metabolite) and 4Ј-hydroxynimesulide (3) (oxidative metabolite) have been reported as minor and major metabolites of 1, respectively, in urine and feces [4][5][6] of man (Chart 1).Further 1 is a protonophore and mitochondrial NAD(P)H oxidant agent whereas 2 has been reported as supressor of the above mitochondrial responses.7) It has also been shown that the reduced metabolite (2) partly protects against accumulation of reactive oxygen species (ROS) derived from the organelle under conditions of oxidative stress.7) The combination of sodium borohydride and metalloporphyrins have been shown to mimic the various redox transformations of organic substrates catalyzed by cytochrome P450 and NAD(P)H, in absence or presence of molecular oxygen. [8][9][10][11][12][13][14] Herein, we report the biomimetic reduction of 1 with sodium borohydride catalyzed by metalloporphyrins in organic solvents under anaerobic and aerobic conditions.In a typical run sodium borohydride (1200 mmol) was added to a mixture of 1 (100 mmol) and 5,10,15,20-tetraphenylporphyrinatoiron(III) chloride (TPPFe(III)Cl, 1 mmol) in methanol : dichloromethane (9 : 1, v/v) under nitrogen atmosphere. The reaction was stirred for 1 h at room temperature. The progress of the reaction was monitored by TLC and HPLC. The solvent was removed under reduced pressure and the residue was chromatographed on silica gel to give 2 in 89% yield (Chart 2, Table 1). The formation of 2 was confirmed by comparison of HPLC retention time as well as other spectroscopic data 15) with that of authentic sample.The presence of molecular ion peak at 277 in electron impact (EI)-MS shows the complete reduction of 1 to 2. Further, the presence of a peak at 199 shows the loss of -SO 2 CH 3 group from the parent molecule. The appearance of broad singlet at 3.7 ppm in 1 H-NMR shows the presence of -NH 2 group in the compound. The upfield chemical shifts of aromatic protons show the complete reduction of nitro group to amino group. The presence of two peaks around 3394 and 3339 cm Ϫ1 in IR spectrum also confirms the formation of 2. The reduction of nimesulide is directly proportional to the substrate, NaBH 4 and iron(III) porphyrin ratio under N 2 atmosphere. As the ratio of iron(III) porphyrin and NaBH 4 is increased to 1 : 1200 mmol the reduction of nimesulide has c...

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“…Oxygenation of olefins by molecular oxygen was performed in the presence of NaBH 4 and metal catalysts such as Mn III , 177,178 Co II ,179 and Fe III (eq 42). 180,181…”

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confidence: 99%