Copper-Free Asymmetric Allylic Alkylation of Trisubstituted Cyclic Allyl Bromides Using Grignard Reagents

Catalytic Generation and Chemoselective Transfer of Nucleophilic Hydrides from Dihydrogen

Copper(I)-N-heterocyclic-carbene (NHC) complexes enabled the catalytic generation of nucleophilic hydrides from dihydrogen (H₂ ) and their subsequent transfer to allylic chlorides. The highly chemoselective catalyst displayed no concomitant hydrogenation reactivity; in fact, the terminal double bond formed in the hydride transfer remained intact. Switching to deuterium gas (D₂ ) allowed for regioselective monodeuteration with excellent isotope incorporation.

Catalytic Enantioselective and Diastereoselective Allylic Alkylation with Fluoroenolates: Efficient Access to C3-Fluorinated and All-Carbon Quaternary Oxindoles

Synthetically versatile 3,3-disubstituted fluorooxindoles exhibiting vicinal chirality centers were obtained in high yields and with excellent enantio-, diastereo-, and regioselectivity through catalytic asymmetric fluoroenolate alkylation with allylic acetates. The reaction proceeds under mild conditions and can be scaled up without compromising the asymmetric induction. The unique synthetic usefulness of the products is highlighted by the incorporation of additional functionalities and the formation of 3-fluorinated oxindoles exhibiting an array of four adjacent centers of chirality. A new C-F bond functionalization path that provides unprecedented possibilities for the stereoselective generation of a chiral quaternary carbon center in the alkaloid scaffold is introduced.

Enantioselective construction of branched 1,3-dienyl substituted quaternary carbon stereocenters by asymmetric allenyl Claisen rearrangement

The availability of enantiomerically enriched 1,3-dienyl substituted quaternary stereocenters is highly valuable for the synthesis of complex natural compounds. Despite great advances in the area of construction of alkenyl-substituted types, a general, practical catalytic system that works for enantioselective formation of 1,3-diene derivatives still remains to be developed. Herein, we disclose the first asymmetric Claisen rearrangement of allenyl vinyl ethers to access optically active β-ketoesters, containing branched 1,3-butadienyl substituted stereocenters. A variety of substrates bearing a range of useful functional groups were well tolerated, thus affording the corresponding products with excellent enantioselectivities (up to 99% ee) and high yields (up to 91%).

Synthesis of quaternary carbon stereocenters by copper-catalyzed asymmetric allylic substitution of allyl phosphates with arylboronates

A copper-catalyzed asymmetric allylic substitution of γ,γ-disubstituted allyl phosphates with arylboronates has been developed for the construction of quaternary stereocenters. High regio- and enantioselectivities have been achieved by employing a hydroxy-bearing chiral N-heterocyclic carbene ligand, and both E and Z substrates provide the same enantiomer as the major product. The mechanistic aspect of this catalysis has also been investigated to find that a 1:1 copper/ligand complex is most likely responsible for the present asymmetric catalysis, and the reaction proceeds with almost perfect 1,3-anti stereochemistry with respect to the allylic electrophile.

Transition metal-free asymmetric and diastereoselective allylic alkylation using Grignard reagents: construction of vicinal stereogenic centers via kinetic resolution

The first transition metal-free catalyzed diastereoselective and enantioselective asymmetric allylic alkylation (AAA) has been disclosed leading to the construction of vicinal tertiary/quaternary centers via a kinetic resolution protocol starting from readily available starting materials.