Ag(I)-Fesulphos-Catalyzed Enantioselective Synthesis of 3-Silylproline Derivatives.

An efficient catalytic asymmetric 1,3-dipolar cycloaddition of N-benzylidineiminoglycinate-derived azomethine ylides to β-silylmethylene malonates catalyzed by a Ag(I)-Fesulphos complex has been developed, affording fully substituted 3-silylproline derivatives with an all carbon quaternary center. The silylproline derivatives were obtained in moderate-to-good yields (up to 81%) in high diastereoselectivities and enantioselectivities (dr up to 95:5; er up to 96:4). Tamao-Fleming oxidation of selected 3-silylproline derivatives provided not only an efficient route but also the shortest route to 3-hydroxyproline derivatives, which are not accessible by direct 1,3-dipolar cycloadditions of azomethine ylide with frequently used arylidene/alkylidene malonates.