New route to 4,4,6,7-tetrasubstituted pentacyclo[6.3.0.0 2,6.0 3.10.0 5,9]undecanes

Abstract

The reactions of 3,6-dibromo-2,7-dioxotetracyclo[6.3.0.0 4,11.0 5,9]undecane with organomagnesium halides are investigated as a method of preparing unusual tetrasubstituted pentacycloundecanes (D 3-trishomocubanes). The tetrasubstituted pentacycloundecanes have been characterized and product geometries confirmed by NMR and X-ray crystal structure analysis. Rel-(1R,2R,3S,4S,5R,6R,7S,8S,9R,10R)-4-hydroxy-4-phenyl-6-methyl-7-bromo-(D 3)-trishomocubane ( 11) exhibits a sterically locked phenyl group with a rotation barrier > 17 kcal/mol which should make possible the preparation of stable rotational isomers with o- or m-substituted phenyl groups.