The facial influence and synthetic utility of oxygen, sulfur and carbon atoms adjacent to the ketone in the series of α-spiro ketones 2, 3, and 4 upon nucleophilic addition has been examined. Addition to the carbonyl group displayed a preference for attack anti to the heteroatom in competition with carbon in synthetically useful ratios. Hydride reduction of 2 with chelating reagenst (NaBH4, LiAlH4 etc.) reversed this facial preference.
Dimitroff, M., & Fallis, A. G. (1998). Studies of π-diastereofacial selectivity: Spiro 2-tetrahydrofuran and 2-tetrahydrothiophene ketones. Tetrahedron Letters, 39(17), 2531–2534. https://doi.org/10.1016/S0040-4039(98)00407-9