Epoxidations of Alkenes Catalyzed by Early Transition Metals

Epoxidations of Alkenes Catalyzed by Early Transition Metals 

High-valent early transition metals like titanium(IV) and vanadium(V) have been shown to efficiently catalyze the epoxidation of alkenes. The preferred oxidants using these catalysts are various alkyl hydroperoxides, typically tert-butyl hydroperoxide (TBHP) or ethylbenzene hydroperoxide (EBH P). One of the routes for the industrial production of propylene oxide is based on a heterogeneous Ti ySi02 catalyst, which employs EBHP as the terminal oxidant [6]. 

In particular, the AE reaction on cis-substituted alkenes, which normally tend to give lower enantioselectivities, resulted in excellent ees employing catalyst 3. In addition, this epoxidation protocol tolerates the use of aqueous TBHP, and does not suffer from the ligand deceleration effects normally observed for vanadium catalysts. 

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Epoxidations of Alkenes Catalyzed by Early Transition Metals 39 2.3... 

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