Transition‐Metal‐Catalyzed Hydroarylation Reactions of Alkynes Through Direct Functionalization of C–H Bonds: A Convenient Tool for Organic Synthesis

Abstract

Direct functionalization of aromatic C–H bonds with alkynes provides an efficient synthetic protocol involving fewer reaction steps without need for prefunctionalization. This microreview presents an overview of the recently developed transition‐metal‐catalyzed hydroarylation reactions of alkynes. Special attention is paid to hydroarylation through alkyne activation processes and through arene activation processes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A decarboxylative approach for regioselective hydroarylation of alkynes

“…The addition of an arene to an alkyne is one attractive route to these structures because of the commercial and synthetic availability of both reagents [1][2][3][4][5] . Such alkyne hydroarylations are more atom efficient and produce less salt waste than catalytic coupling of alkynes with pre-functionalized aromatic compounds (Fig.…”

“…In recent years, various transition-metal catalysts have been developed for alkyne hydroarylation via the formal activation of arene C-H bonds to form metal-aryl intermediates 4,5 . A number of these reported catalysts are Lewis acidic and cleave the C-H bond by electrophilic aromatic substitution, which is mechanistically analogous to the Friedel-Crafts reaction and leads to similar limitations on regioselectivity ( Fig.…”

“…This chelationassisted C-H functionalization strategy was explored further by Murai and co-workers for the ruthenium-catalysed hydroarylations of alkenes and alkynes with aromatic ketones 15,16 . Since these pioneering studies, chelation-assisted alkyne hydroarylation has been explored with various transition-metal catalysts and a wide range of heteroatom-based directing groups 4,6,[17][18][19][20] . However, removal of these ortho-directing groups from the hydroarylation products requires additional chemical transformations and is not always achievable [21][22][23] .…”

CH Alkenylations with Alkenyl Acetates, Phosphates, Carbonates, and Carbamates by Cobalt Catalysis at 23 °C

“…Thus, for example, Nakamura, our group, Yoshikai, and Kanai have recently developed cobalt-catalyzed C À H functionalizations with organic electrophiles. [6,7] As of yet, cobalt-catalyzed C À H olefinations have been solely accomplished through hydroarylations [8] of alkynes. [7,9] Despite significant advances by Yoshikai and coworkers, [10,11] this approach continues to face considerable limitations, including the difficulty of controlling regioselectivity as well as the inherent limitation to the synthesis of acyclic alkenes.…”

Palladium‐Catalyzed Enantioselective Intramolecular Hydroarylation of Alkynes To Form Axially Chiral 4‐Aryl 2‐Quinolinones

“…[2] A large number of transition-metal catalysts have been developed to date for this transformation. [3] Research efforts have been focused on catalytic efficiency, substrate scope, and regioselectivity (6-endo-dig versus 5-exodig [4] ), whereas no enantioselective variant of this transformation has been reported.…”