Adamantyl cation methyl-substituted

The 2-methyl, 2-cyclopropyl and 2-phenyl substituted 8,9-dehydro-2-adamantyl cations 25 were prepared from their respective alcohols using fluorosulfuric acid in sulfuryl chloride fluoride at low temperatures (equation 27). The relative extent of charge delocalization in these cations was estimated by comparing their NMR spectra. The ions are nonequilibrating static cations, as shown by their proton NMR spectra56. 

Cyclobutyl, substituted cyclobutyl, and related carbocations were reviewed.23 A study of the photophysical properties and photochemistry of 1-adamantyl aryl ethers in methanol solvent showed that, although the majority of the ethers underwent photolysis by homolytic pathways, irradiation of the 4-cyanophenol ether resulted, in part, in the methyl ether, implicating an ionic mechanism with the 1-adamantyl cation as an intermediate.24 Labelling experiments demonstrated that the fragmentation of 7-norbomyloxychlorocarbene to 7-norbornyl chloride proceeds with both retention and inversion.25 While an ion pair [Cl CO R+] is a possible intermediate, computational studies suggest that the fragmentations proceed via transition states that lead to either retention or inversion. 

Methyl substituted adamantyl cations have also been studied103. The bridgehead homoadamantyl cation 42 has been obtained104 from both adamantylcarbinyl and homoadamantyl precursors. Bridgehead bicyclo [4.4.0] decyl, bicyclo [4.3.0] nonyl... 

Another feature of systems that are subject to B-strain is their reluctance to form strained substitution products. The cationic intermediates usually escape to elimination products in preference to capture by a nucleophile. Rearrangements are also common. 2-Methyl-2-adamantyl p-nitrobenzoate gives 82% methyleneadamantane by elimination and 18% 2-methyl-2-adamantanol by substitution in aqueous acetone. Elimination accounts for 95% of the product from 2-neopentyl-2-adaman l p-nitrobenzoate. The major product (83%) from 2-r-butyl-2-adamantyl p-nitrobenzoate is the rearranged alkene 5. 

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. 

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