Ru(II)-Pheox Catalyzed Highly Stereoselective Cyclopropanation of Allyl- and Vinylsilanes with Diazoesters and Their Synthetic Applications

The stereoselective synthesis of optically active cyclopropylsilanes from various allyl- and vinylsilanes with functionalized diazoesters was achieved in excellent yields (up to 99 %) and diastereo- (up to >99 : 1 d.r.) and enantioselectivities (up to 99 % ee) in the presence of Ru(II)-Pheox catalysts. Among a series of Ru(II)-Pheox catalysts, p-MeO-Ru(II)-Pheox was determined to be the best catalyst for cyclopropanation reactions of diazoesters with various allylsilanes. Also, methyl(diazoacetoxy)acetate afforded in significantly enhanced yields, diastereoselectivities, and enantioselectivities. The cyclopropanation reactions with vinylsilanes with methyl (diazoacetoxy)acetate proceeded with excellent diastereoselectivities (>99 : 1 d.r.). Moreover, cyclopropylsilane derivatives could be successfully transformed into beneficial building blocks for the synthesis of bioactive compounds, including an anti-HIV drug and Imatinib-7.