Bridgehead functionalisation of saturated hydrocarbons with lead(IV) salts

Abstract

Oxidation of a series of adamantanes, bicyclo[3.3.1]nonane, and diamantane with lead tetra-acetate in trifluoro acetic acid–dichloromethane solution in the presence of chloride ion at room temperature gives high yields of the trifluoroacetates of the bridgehead alcohols (based both on oxidant and on hydrocarbon). By subsequent hydrolysis bridgehead alcohols are obtained in >88% overall yields from adamantane and 1-alkyladamantanes; bicyclo[3.3.1]nonane gives bicyclo[3.3.1]nonan-1-ol (88%), and diamantane gives a mixture of diamantan-1-ol and diamantan-4-ol in a ratio controlled by the reaction conditions. Further equilibration of the trifluoroacetate of diamantan-1-ol gives a 1 : 1 mixture of the trifluoroacetates of diamantan-1-ols and -4-ols. The high selectivity is illustrated by very low reactivity with methylcyclohexane and 3-methylhexane, and the deactivating influence of the trifluoroacetate group protects the primary products from further oxidation. Further adamantanes with an electron-withdrawing 1-substituent show low reactivity and either give products in low yield or do not react. The trifluoroacetate group is readily displaced by reaction with acetonitrile in ‘one-pot’ conversion of hydrocarbons into amides.