Titanocene-Catalyzed Reductive Epoxide Opening: The Quest for Novel Hydrogen Atom Donors

Abstract

Novel hydrogen atom donors for the reductive titanocene-catalyzed epoxide opening are presented. While the potentially attractive cyclopentadienes gave only moderate yields of the desired alcohols, substituted, nontoxic, and commercially available 1,4-cyclohexadienes, e.g. γ-terpinene, in combination with more elaborate catalysts gave better or similar results than the much more expensive and carcinogenic 1,4-cyclohexadiene. In the practically important reactions of Sharpless epoxides and their derivatives excellent levels of regioselectivity for the epoxide opening could be obtained. The toxic and unpleasant to handle tert-butyl thiol could be replaced while increasing the yields of the desired products.

epoxides - titanium - reductive ring opening - H-atom donors - γ-terpinene

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