Gif-Orsay system

The Gif and Gif-Orsay systems exhibit some unusual characteristics. Most importantly, they oxidize secondary carbon preferentially and ketones not alcohols are the main products 160... 

Gif-Orsay system OH, OAc, pyridine Selective oxidation of saturated hydrocarbons 3.2.2. 

The chemical (Gif system) and the electrochemical conversion (Gif-Orsay system) have been compared in the oxidation of six saturated hydrocarbons (cyclohexane, 3-ethylpentane, methylcyclopentane, cis- and traus-decalin and adamantane). The results obtained for pyridine, acetone and pyridine-acetone were similar for both systems. Total or partial replacement of pyridine for acetone affects the selectivity for the secondary position and lowers the ratio ketone secondary alcohol. The formation of the same ratio of cis- and traws-decal-9-ol from either cis- or trans-deca in indicates that tertiary alcohols result from a mechanism essentially radical in nature. The C /C ratio between 6.5 and 32.7 rules out a radical mechanism for the formation of ketones and secondary alcohols. Ratios of 0.14 and 0.4 were reported for radical-type oxidations of adamantane and cis-decalin. Partial replacement of pyridine by methanol, ethanol or f-propanol results in diminished yields and a lower selectivity. Acetone gives comparable yields however, the C /C ratio drops to 0.2-10.7. 

The first Gif-Orsay system (Pt-anode, Hg-cathode, cpe, TEABF4 in pyridine-acetic acid, divided cell) converted adamantane to 3.5% 1-adamantanol, 0.7% 2-adamantanol and 3.0% adamantone. Replacement of acetic acid by trifluoroacetic acid and its continuous addition to maintain a constant acidity improved the coulombic yield and selectivity. The oxidation of adamantane yielded 18% product with a C /C ratio of 8.5, this one of cyclodecane 21.1% product, and this one of trans-decalin 22.2% product, with a C /C ratio of 36. The results come close to those obtained in the chemical system. The third system... 

The related Gif-Orsay system consists of components similar to those of the Gif systems with the exception that the electrons are provided by electric current, i.e. cathodic reduction is employed [127,128]. 

Balavoine, G., Barton, D.H.R., Boivin, J., Gref, A., Le Coupanec, P., Ozbalik, N., Pestana, J.A.X., and Riviere, H. (1988) Functionalisation of Saturated Hydrocarbons. Part X.l. A Comparative Study of Chemical and Electrochemical Processes (Gif and Gif-Orsay Systems) in Pyridine, in Acetone and in Pyridine-Co-Solvent Mixtures, Tetrahedron 44,1091-1106. 

The nomenclature is geographical. Gif stands for Gif-sur-Yvette in France where Gif through Gif were invented. GoAgg stands for Gif-Orsay-Aggieland, introducing work done at the Universite de Paris-Sud and Texas A M University. Ch comes from Chernogolovka (USSR), where the GoChAgg system was discovered. 

The Gif system, which consists of triplet oxygen, acetic acid, pyridine, zinc and an iron catalyst, oxidizes saturated hydrocarbons mainly to ketones and gives minor amounts of aldehydes. Tertiary hydrogen is only substituted in exceptional cases. With the Gif-Orsay II system in which zinc is replaced by the cathode [divided cell, cpe at — 0.6 to —0.7 V vs see, trifluoroacetic acid, pyridine, Fe30(0Ac)6Pyr3.5], adamantane is converted in 3.8% coulombic yield the ratio of attack at a secondary tertiary CH bond (C /C ratio) is 15.0. Comparable conversions were carried out with cyclododecane to afford 21% oxidation with a ratio of alcohol ketone = 1 14. TranS decalin yielded 22% product, consisting of 0.6% 9-ol, 0.9% l-ol, 9.0% 1-on 0.65% 2-ol and 11% 2-one. A radical mechanism for this conversion can be excluded since for the cobalt-catalyzed radical oxidation of trans-decalin the C /C ratio is 0.13, which is far removed from 36 found with the Gif system. 

The Gif-Orsay II system has been further improved in yields and simplified with respect to the reaction conditions. Cyclododecane, adamantane and cyclooctane are oxidized in 17-30 mmolar amounts and coulombic yields of around 30% with oxygen, pyridine, trifluoroacetic acid and an iron catalyst in an undivided cell. Cyclododecane afforded a 18.9% yield of alcohol and ketone in a ratio of 0.14, adamantane a 14% coulombic yield, cyclooctane and cyclohexane coulombic yields up to 48%. The C /C ratio with adamantane reached values up to 40. With paraquat or 4,4 -bipyridyl as electron transfer reagent and under otherwise the same conditions, a coulombic yield of 49% cyclohexanol and cyclohexanone (1 7.88) was obtained. In this process oxygen is reduced to superoxide, which oxidizes iron(II) to an active iron catalyst that is able to react with the hydrocarbon. 

Gif Chemistry Barton has reported an interesting series of oxidation catalysts, based on Fe(II) and Zn/Oz or Fe(II) and ROOH, which are referred to as the Gif, Gif-Orsay, and Go-Agg system. The unusual selectivity for hydroxylation and ketonization of alkanes led to the rejection of the t3rpical radical-based mechanisms often seen in metal ion-(>2-alkane reactions. One of the suggestions currently under discussion is the formation of direct Fe—C... 

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