Synthesis of Terpene and Steroid Dimers and Trimers Having Cyclobutadienyl−Co and Aromatic Tethers

The reaction of natural product derived propargylic alcohols with CpCo(CO)2 produces three new types of natural product hybrids having two or three terpene or steroid fragments. The tether joining the natural product subunits is built during the reaction. Type 1 hybrids have two terpene or steroid moieties joined by a CpCo−cyclobutadiene tether, with the two units disposed in a 1,2-arrangement (9, 14, 22). Type 2 hybrids have a Co−cyclopentadienone tether (10). Type 3 has three units of terpene or steroid joined to a benzene ring (11, 12, 15). An unusual Co-mediated β-carbon elimination pathway of propargylic alcohols leading to ketones (an unknown process in this chemistry) has been observed.