Synergistic catalysis for stereocontrol of prochiral nucleophiles in palladium-catalyzed asymmetric allylic substitution

In contrast to the stereocontrol of the stereocenter at the allyl unit,the asymmetric induction of prochiral nucleophiles remains a challenge in Pd-catalyzed asymmetric allylic substitutions due to the remote distance between the chiral catalyst and the stereocenter established at prochiral nucleophile.Much effort has been devoted to solving this challenge through the elaborate design of chiral ligands.Recently,synergistic catalysis has gained increasing attention owing to its potential advantages over the traditional single palladium catalysis,such as improvement of reactivity and selectivity.This strategy,including bimetallic catalysis and Pd/organocatalysis,not only broadens the scope of prochiral nucleophiles,but also provides a simple and unified method for the stereocontrol of prochiral nucleophiles.This review summarizes the brief history and advances in this field.

Stereodivergent Pd/Cu Catalysis for Asymmetric Desymmetric Alkylation of Allylic Geminal Dicarboxylates

AstereodivergentPd/Cucatalyst systemforasymmetric desymmetric alkylation of allylic geminal dicarboxylates has been developed,which was successfully applied to the asymmetric synthesis of β-hydroxycarbonylmotifs bearing a versatile carbon-carbon double bond in an enantio-and diastereodivergent manner.A wide scope of substrates including challenging alkylsubstituted,2-substituted,and3,3′-disubstitutedallylic species are compatible with this catalytic system,delivering the substituted products in high to excellent yieldsandwith excellent diastereo-(upto>20:1 dr)and enantioselectivities(up to>99%ee).Furthermore,the mechanism of this dual Pd/Cu catalytic system including:(1)the desymmetrization process ofgeminal dicarboxylates;(2)the origin of regioselectivity(branched or linear);(3)the enantio-and diastereoselectivity observed by changing the combinations of two chiral metal catalysts,have been carefully investigated by theoretical calculations.

Enantioselective synthesis of 10-allylanthrones via iridium-catalyzed allylic substitution reaction

A highly enantioselective allylic substitution reaction of anthrones with aromatic or aliphatic allyl carbonates was realized by using iridium catalyst prepared from [Ir（COD）CI]2 and BHPphos. Substituted 10-allylanthrones were obtained in excellent yields and with excellent enantioselectivity and regioselectivity （up to 98% yield, 99700 ee） under mild conditions.