Reductive coupling (TiCl3/Li) gives (adamantylidene)adamantane, an example of a general method for the synthesis of highly-substituted alkenes: Org. Synth. Coll., 7, 1 (1990). Preparation of highly-substituted alkenes by the Wittig reaction gives poor yields with adamantanone. The route involving addition of a Grignard or alkyllithium reagent is to be preferred: J. Org. Chem., 54, 1375 (1989).
