Copper‐Catalyzed Enantioselective Markovnikov Protoboration of α‐Olefins Enabled by a Buttressed N‐Heterocyclic Carbene Ligand

• Published in: Angewandte Chemie International Edition Vol. 57; no. 5; pp. 1376 - 1380
• Main Authors: Cai, Yuan, Yang, Xin‐Tuo, Zhang, Shuo‐Qing, Li, Feng, Li, Yu‐Qing, Ruan, Lin‐Xin, Hong, Xin, Shi, Shi‐Liang
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 26.01.2018; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Alkenes; Ambient temperature; asymmetric synthesis; Buttresses; Chemistry; Chemistry, Multidisciplinary; Copper; Enantiomers; Esters; Functional groups; ligand design; Ligands; N-heterocyclic carbenes; olefins; Physical Sciences; Regioselectivity; Science & Technology; Substrates; TRANSITION-METAL CATALYSIS; STYRENES; TRISUBSTITUTED ALKENES; ASYMMETRIC HYDROBORATION; olefins; DESYMMETRIZATION; TERTIARY BORONIC ESTERS; CROSS-COUPLING REACTIONS; asymmetric synthesis; ligand design; copper; 1,1-DISUBSTITUTED ARYL ALKENES; UNACTIVATED TERMINAL ALKENES; ADDITIONS; N-heterocyclic carbenes
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201711229

Reported is a highly enantioselective copper‐catalyzed Markovnikov protoboration of unactivated terminal alkenes. A variety of simple and abundant feedstock α‐olefins bearing a diverse array of functional groups and heterocyclic substituents can be used as substrates, and the reaction proceeds under mild reaction conditions at ambient temperature to provide expedient access to enantioenriched alkylboronic esters in good regioselectivity and with excellent enantiocontrol. Critical to the success of the protocol was the development and application of a novel, sterically hindered N‐heterocyclic carbene, (R,R,R,R)‐ANIPE, as the ligand for copper. By design: A highly enantioselective copper‐catalyzed Markovnikov protoboration of α‐olefins is described. This mild and general process effectively converts simple and abundant feedstock α‐olefins into a diverse array of chiral alkylboronic esters with excellent enantiocontrol. Key to the success of the protocol was the use of a newly developed, sterically hindered N‐heterocyclic carbene, (R,R,R,R)‐ANIPE, as the ligand.