Catalytic cycloalumination in steroid chemistry: the introduction of a spirotetrahydrofuran or spirotetrahydroselenophene moiety into a 3'-methylene-(5α)-spirocholestane-3,1'-cyclobutane molecule.

Cycloalumination of 3'-methylene-(5α)-spirocholestane-3,1'-cyclobutane with triethylaluminum catalyzed by Cp(2)ZrCl(2) was accomplished for the first time to give (5α)-spirocholestane-3,1'-(6'-ethyl-6'-aluminaspiro [3.4] octane) in 89%. The latter, without isolation, was converted into spirotetrahydroselenophene or spirotetrahydrofuran.