Highly Enantioselective Regiodivergent Allylic Alkylations of MBH Carbonates with Phthalides

Phthalides were used for the first time in the allylic
alkylation
reactions with MBH carbonates for the creation of chiral 3,3-disubstituted
phthalides. Highly enantioselective regiodivergent synthesis of γ-selective
or β-selective allylic alkylation products was achieved by employing
bifunctional chiral phosphines or multifunctional tertiary amine–thioureas
as the catalyst, respectively. It was demonstrated that proper selection
of catalysts and reaction conditions would differentiate an SN2′–SN2′ pathway and an addition–elimination
process, yielding different regioisomers of the allylic alkylation
products in a highly enantiomerically pure form.