Formation and cleavage of bisnoradamantane derivatives through SmI2 reductions

The strain of the bisnoradamantane skeleton is shown by: (i) the easy homoketonization of tricyclo[3.3.0.03,7]octane-1,5-diol, 2a, to exo-7-hydroxy-cis-bicyclo[3.3.0]octan-3-one, 3a, under silica gel column chromatography, and (ii) the cleavage of the C3–C7 bond of 1,5-dimethyl-3,7-dipivaloyltricyclo[3.3.0.03,7]octane, 9, to give bicyclo[3.3.0]octane diketones, under attempted SmI2-intramolecular pinacolization. In contrast, 2a was obtained by SmI2-pinacolization of cis-bicyclo[3.3.0]octane-3,7-dione, 1a.