Adamantane anodic oxidation

Alkyl cations thus formed may recombine with the nucleophile (Eq. 10) giving tri-fluoroacetates or acetamides under anodic oxidation conditions in CF3COOH or CH3CN, respectively. For example, electrooxidation of cyclohexane (7) in CH2C12/ CF3COOH yielded 84 % cyclohexyl trifluoroacetate (15) [23] oxidation of adamantane (9) gave acetamide (16) cleanly (Scheme 4) [24]. 

In the anodic oxidation, adamantane is a unique compound among alkanes. It has a rather low oxidation potential, and its anodic oxidation in acetonitrile affords acetamidoadamantane (1 equation 6) in 90% yield.<... 

In general, treatment of carbonium ions with nitriles under a variety of conditions yields A -substituted amines. Anodic oxidation in acetonitrile converts selected aliphatic compounds to acetamides, e.g. adamantane to adamantylacetamide (equation 22). ... 

TABLE 7. Distribution of products from anodic oxidation of alkyl-substituted adamantanes in acetonitrile... 

The comparison of the oxidation of a series of substituted adamantanes (t-butyl, methyl, adamantyl) by lead(IV), cobalt(III) and manganese(III) trifluoroacetates with the corresponding anodic oxidations in acetonitrile or trifluoroacetic acid shows that the electrochemical oxidation proceeds via a radical cation intermediate, whilst the metal salts form products by CH abstraction". The preparative result is that, in anodic oxidation, preferentially products of fragmentation of the intermediate radical cation are found, whilst with the metal salts hydrogen substitution is being obtained preferentially. 

In the wake of the early work just described, several investigations of anodic acet-amidation of polycyclic hydrocarbons were initiated substituted adamantanes were much used in this work because of their availability and their relative ease of oxidation [1 VO-174]. The results are generally explicable in terms of expected stabilities of intermediate carbocations and competition between proton loss and C-C bond cleavage. Difunctionalization of adamantanes is also possible using anodic acetamidation [Eq. (50)] [174]. 

The anodic conversion of tertiary C—H functions (without any specific activation) is possible, yet it needs rather high potentials. One typical example is certainly that of adamantane [42], the oxidation of which can be achieved in acetonitrile. Under these conditions, the corresponding acetamide (via Ritter reaction) was obtained. 

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... 

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