Homogeneous catalysis. Metallocene catalysts for [3+2] nitrone-olefin cycloaddition reactions

The complex [Cp2Ti(OTf)(2)] is a catalyst for the [3+2] cycloaddition of ni trones with electron-rich olefins. In the presence of small amounts of wate r, 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 [Cp2Ti(nitrone)(2)](2+). A crystal structure of one of these adducts is reported.