Ni/Photoredox-Catalyzed Enantioselective Cross-Electrophile Coupling of Styrene Oxides with Aryl Iodides

Abstract

A Ni/photoredox-catalyzed enantioselective reductive coupling of styrene oxides and aryl iodides is reported. This reaction affords access to enantioenriched 2,2-diarylalcohols from racemic epoxides via a stereoconvergent mechanism. Multivariate linear regression (MVLR) analysis with 29 bioxazoline (BiOx) and biimidazoline (BiIm) ligands revealed that enantioselectivity correlates with electronic properties of the ligands, with more electron-donating ligands affording higher ee’s. Mechanistic studies were conducted, lending support to the hypothesis that the electronic character of the ligands influences the enantioselectivity by altering the position of the transition state structure along the reaction coordinate. This study demonstrates the benefits of utilizing statistical modeling as a platform for mechanistic understanding and provides new insight into an emerging class of chiral ligands for stereoconvergent Ni and Ni/photoredox cross-coupling.

Three-Component Asymmetric Ni-Catalyzed 1,2-Dicarbofunctionalization of Unactivated Alkenes via Stereoselective Migratory Insertion

“…We performed density functional theory (DFT) calculations at the M06/SDD-6-311++G(d,p)/SMD(i-BuOH)//B3LYP-D3(BJ)/SDD-6-31+G(d,p) level of theory (see the SI for computational methods) to investigate the reaction mechanism and the role of the Bn-biOx ligand on enantioinduction. 16 Because of the potentially hemilabile nature of the Bn-biOx ligand 2d and the conformational flexibility of its benzyl groups, a careful conformational analysis was performed using a workflow that consists of CREST/GFN2-xTB 17 conformational sampling followed by DFT geometry optimizations of low-energy transition state conformers (see the SI for details). The computed reaction energy profile is shown in Figure 1.…”

Recent Progress on Transition-Metal-Mediated Reductive C(sp3)–O Bond Radical Addition and Coupling Reactions

“…The same group has further utilized a chiral bisimidazoline (BiIm) ligand for asymmetric epoxide radical ring opening/arylation to afford 2-hydroxy biaryl ethane products with high enantioselectivities (Scheme 3b ). 11 The authors analyzed the results of bisoxazoline (BiOx) and bisimidazoline (BiIm) ligands using statistical modeling to identify the structure–selectivity relationship, wherein higher ee values correlate with better electron-donating ligands.…”

Enantioselective Reductive Cross‐Coupling of Aryl/Alkenyl Bromides with Benzylic Chlorides via Photoredox/Biimidazoline Nickel Dual Catalysis

“…[4] Mao and co-workers recently reported a photo-driven nickel-catalyzed RCC reaction using chiral bioxazoline (BiOx) ligand with soluble reductant instead of metal dust (Scheme 1b). [5][6] Although these examples explored the asymmetric RCC reactions, problems still exist particularly in photocatalytic reactions: 1) expensive and highly reactive aryl iodides are required for the initiation of oxidative addition with nickel catalysts. [7] To the best of our knowledge, there is only one example using aryl bromide as C(sp 2) electrophile reported very recently by the Doyle group [6b] showing a decreased reactivity and no example using chlorides as C(sp 2) electrophile was reported.…”