The Isomerisation of Homoadamantane-3-carboxylic Acid into Homoadamantane-1-carboxylic Acid
It is shown by D-, 13C-, and double labelling experiments that the title isomerisation 2 -> 3 under Koch-Haaf conditions is due to reversible decarbonylation followed by intermolecular hydride transfer between the bridgehead positions of the two bridgehead homoadamantane cations and homoadamantane derivatives.The isomerisation is accompanied by complete equilibration of an isotopically labelled methylene group over all possible positions.This is due to the known adamantylmethyl-3-homoadamantyl cation rearrangement which is likewise occuring.In contrast to hydride transfer reactions in the adamantyl system the methylene groups of the homoadamantyl system are not participating in the hydride transfer between the bridgehead positions.