Titanocene(III)‐Catalyzed Precision Deuteration of Epoxides

We describe a titanocene(III)‐catalyzed deuterosilylation of epoxides that provides β‐deuterated anti‐Markovnikov alcohols with excellent D‐incorporation, in high yield, and often excellent diastereoselectivity after desilylation. The key to the success of the reaction is a novel activation method of Cp(2)TiCl(2) and (tBuC(5)H(4))(2)TiCl(2) with BnMgBr and PhSiD(3) to provide [(RC(5)H(4))(2)Ti(III)D] without isotope scrambling. It was developed after discovering an off‐cycle scrambling with the previously described method. Our precision deuteration can be applied to the synthesis of drug precursors and highlights the power of combining radical chemistry with organometallic catalysis.