Homogeneous Catalysis. Metallocene Catalysts for [3+2] Nitrone−Olefin Cycloaddition Reactions

The complex [Cp 2 Ti(OTf) 2 ] is a catalyst for the [3+2] cycloaddition of nitrones with electron-rich olefins. In the presence of small amounts of water, catalyst hydrolysis leads to the production of triflic acid, which is a powerful catalyst for these cycloaddition reactions. Acid catalysis can be suppressed by the use of Proton-Sponge. Metal catalysis appears to proceed via the bis(nitrone) adduct [Cp 2 Ti(nitrone) 2 ] 2+ . A crystal structure of one of these adducts is reported.