Pd-Catalyzed Selective Chlorination of Acrylamides at Room Temperature

Catalyst-Free Regio- and Stereoselective C(sp2)-H Chlorination of Enamides at Room Temperature

We disclose herein a catalyst-free, room-temperature protocol for the highly regio- and stereoselective alkenyl C(sp2)-H chlorination of diverse enamides with commercially available, inexpensive N-chlorosuccinimide (NCS) as the electrophilic chlorinating reagent under exceedingly mild conditions. This operationally simple approach features a remarkably broad substrate scope and accommodates excellent functional group tolerance, affording a diverse range of synthetically valuable geometrically defined β-chlorinated enamides in high yields with an exclusive E configuration.

Recent Advances in Alkenyl sp2 C-H and C-F Bond Functionalizations: Scope, Mechanism, and Applications

Alkenes and their derivatives are featured widely in a variety of natural products, pharmaceuticals, and advanced materials. Significant efforts have been made toward the development of new and practical methods to access this important class of compounds by selectively activating the alkenyl C(sp²)-H bonds in recent years. In this comprehensive review, we describe the state-of-the-art strategies for the direct functionalization of alkenyl sp² C-H and C-F bonds until June 2022. Moreover, metal-free, photoredox, and electrochemical strategies are also covered. For clarity, this review has been divided into two parts; the first part focuses on currently available alkenyl sp² C-H functionalization methods using different alkene derivatives as the starting materials, and the second part describes the alkenyl sp² C-F bond functionalization using easily accessible gem-difluoroalkenes as the starting material. This review includes the scope, limitations, mechanistic studies, stereoselective control (using directing groups as well as metal-migration strategies), and their applications to complex molecule synthesis where appropriate. Overall, this comprehensive review aims to document the considerable advancements, current status, and emerging work by critically summarizing the contributions of researchers working in this fascinating area and is expected to stimulate novel, innovative, and broadly applicable strategies for alkenyl sp² C-H and C-F bond functionalizations in the coming years.

Switchable, Reagent-Controlled C(sp3)-H Selective Iodination and Acetoxylation of 8-Methylquinolines

An efficient Pd-catalyzed C(sp³)-H selective iodination of 8-methylquinolines is reported herein for the first time. Because of the versatility of organic iodides, the method offers a facile access to various C8-substituted quinolines. By slightly switching the reaction conditions, an efficient C(sp³)-H acetoxylation of 8-methylquinolines has also been enabled. Both approaches feature mild reaction conditions, good tolerance of functional groups, and a broad substrate scope.

Diastereoselective palladium-catalyzed functionalization of prochiral C(sp3)-H bonds of aliphatic and alicyclic compounds

We highlight the reported developments of the palladium-catalyzed C-H activation and functionalization of the inactive/unreactive prochiral C(sp³)-H bonds of aliphatic and alicyclic compounds. There exist numerous classical methods for generating contiguous stereogenic centers in a compound with a high degree of stereocontrol. Along similar lines, the Pd(II)-catalyzed, directing group-aided functionalization of inactive prochiral/diastereotopic C(sp³)-H bonds have been exploited to accomplish the stereoselective construction of stereo-arrays in organic compounds. We present a concise discussion on how specific strategies consisting of Pd(II)-catalyzed, directing group-aided C(sp³)-H functionalization have been utilized to generate two or more stereogenic centers in aliphatic and alicyclic compounds.

Electrochemical oxidative Z-selective C(sp2)-H chlorination of acrylamides

An electrochemical method for the oxidative Z-selective C(sp²)-H chlorination of acrylamides has been developed. This catalyst and organic oxidant free method is applicable across various substituted tertiary acrylamides, and provides access to a broad range of synthetically useful Z-β-chloroacrylamides in good yields (22 examples, 73% average yield). The orthogonal derivatization of the products was demonstrated through chemoselective transformations and the electrochemical process was performed on gram scale in flow.

Z-Selective Pd-catalyzed 2,2,2-trifluoroethylation of acrylamides at room temperature

A straightforward 2,2,2-trifluoroethylation of acrylamides by Pd-catalyzed C-H bond activation was reported by using a fluorinated hypervalent iodine reagent as a coupling partner. At room temperature, this additive-free approach allowed the synthesis of Z-2,2,2-trifluoroethylated acrylamides (19 examples, up to 73% yield) in a stereoselective manner. Under these mild reaction conditions, the methodology turned out to be functional group tolerant and mechanistic studies gave us a better understanding of the transformation.