The Adamantane Rearrangement of Tricyclo[4.2.2.01,5]decane to Tricyclo[5.3.0.04,8]decane

Regioselective generation of the C(2)-carbocation a of tricyclo[4.2.2.0^1,5]decane ( 1 ) by treatment of both corresponding epimeric alcohols 5 and 6 with BF₃ and trapping the rearranged tricyclo[5.3.0.0^4,8]decan-7-yl carbocation b with Et₃SiH as hydride-ion donor (ionic hydrogenation) gives the corresponding hydrocarbon 3 as sole product in almost quantitative yield. The latter is a known intermediate in the Lewis-acid-catalyzed rearrangement of 1 to adamantane ( 4 ).