Cyclic (Alkyl)(amino)carbene Ligands Enable Cu‐Catalyzed Markovnikov Protoboration and Protosilylation of Terminal Alkynes: A Versatile Portal to Functionalized Alkenes. Issue 36 (29th July 2021)

• Record Type: Journal Article
• Authors: Gao, Yang; Yazdani, Sima; Kendrick, Aaron; Junor, Glen P.; Kang, Taeho; Grotjahn, Douglas B.; Bertrand, Guy; Jazzar, Rodolphe; Engle, Keary M.
• Is Part Of: Angewandte Chemie international edition. Volume 60:Issue 36(2021)
• Page Start: 19871
• Page End: 19878
• Publication Date: 2021-07-29
• Subjects: alkyne functionalization -- copper catalysis -- cyclic (alkyl)(amino)carbene -- protoboration -- protosilylation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202106107
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Regioselective hydrofunctionalization of alkynes represents a straightforward route to access alkenyl boronate and silane building blocks. In previously reported catalytic systems, high selectivity is achieved with a limited scope of substrates and/or reagents, with general solutions lacking. Herein, we describe a selective copper‐catalyzed Markovnikov hydrofunctionalization of terminal alkynes that is facilitated by strongly donating cyclic (alkyl)(amino)carbene (CAAC) ligands. Using this method, both alkyl‐ and aryl‐substituted alkynes are coupled with a variety of boryl and silyl reagents with high α‐selectivity. The reaction is scalable, and the products are versatile intermediates that can participate in various downstream transformations. Preliminary mechanistic experiments shed light on the role of CAAC ligands in this process. Abstract : Copper catalysts bearing cyclic (alkyl)(amino)carbene (CAAC) ligands exhibit remarkably high Markovnikov selectivity in the protoboration and ‐silylation of terminal alkynes. This work demonstrates the ability of this strongly σ‐donating family of ligands to perturb regioselectivity in the addition of copper−boryl species to C−C π‐bonds.