Metal Complex-Controlled Regio-, Diastero- and Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylides with Benzo[b]thiophene Sulfones.

The Cu(MeCN)4 PF6 /DTBM-Segphos complex catalyzed the highly diastereo- and enantioselective 1,3-dipolar cycloaddition of azomethine ylides with benzo[b]thiophene sulfones with the usual regiochemistry to give single isomers of the exo-cycloadducts in good yields. In contrast, the AgOAc/ThioClickFerrophos complex catalyzed the reaction with atypical regiochemistry to give the endo-cycloadducts as major products with excellent enantioselectivities. Thus, the choice of chiral metal complex enabled the regio- and stereoselective synthesis of chiral fused sulfolanes.