Diastereo- and Enantioselective Synthesis of 3-Allyl-3-hydroxyoxindoles via Allylation of Isatins.

A highly diastereo- and enantioselective allylation of isatins with 3-substituted allylboronic compounds was achieved by the chiral N,N'-dioxide/Lu(OTf)3 complex. This approach provides an efficient route to useful enantioenriched 3-allyl-3-hydroxyoxindoles with adjacent tetrasubstituted tertiary or tetrasubstituted quaternary stereogenic centers. Density functional theory calculations were performed to understand the different diastereoselection between the background reaction and catalytic process. Moreover, allylation with potassium allyltrifluoroborate was accomplished by the chiral N,N'-dioxide/In(OTf)3 complex. The synthetic utility was demonstrated by further transformation of the product to a tetrahydrofuranyl oxindole derivative.