Catalytic Asymmetric Construction of Spirocycles Containing Pyrrolidine Motifs and Spiro Quaternary Stereogenic Centers via 1,3-Dlpolar Cycloaddltion of Azomethine Ylides with 2-Alkylidene-Cycloketones

摘要

The first catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides with various sterically hindered α,α,β-trisubstituted 2-alkylidene-cycloketones has been developed successfully with silver acetate/TF-BiphamPhos complex for the construction of spiro heterocyclic compounds containing pyrrolidine motifs and a spiro quaternary stereogenic carbon center. The highly efficient catalytic system exhibited high reactivity, excellent diaste-reoselectivity, good enantioselectivity and broad substrate scope under mild conditions. Subsequent transformations led to the expedient preparation of synthetically useful spiro [pyrrolidine-tetrahydropyr-anone] and spiro [pyrrolidine-isochroman-1-one] without loss of the diastereo- and enantiomeric excesses.