More Like this

1. Recent advances in oxidative allylic C–H functionalization via group IX-metal catalysis

   https://doi.org/10.1039/D0CC05554A  

   Kazerouni, Amaan M.; McKoy, Quincy A.; Blakey, Simon B. (November 2020, Chemical Communications)

   null (Ed.)

   Allylic substitution, pioneered by the work of Tsuji and Trost, has been an invaluable tool in the synthesis of complex molecules for decades. An attractive alternative to allylic substitution is the direct functionalization of allylic C–H bonds of unactivated alkenes, thereby avoiding the need for prefunctionalization. Significant early advances in allylic C–H functionalization were made using palladium catalysis. However, Pd-catalyzed reactions are generally limited to the functionalization of terminal olefins with stabilized nucleophiles. Insights from Li, Cossy, and Tanaka demonstrated the utility of RhCp x catalysts for allylic functionalization. Since these initial reports, a number of key intermolecular Co-, Rh-, and Ir-catalyzed allylic C–H functionalization reactions have been reported, offering significant complementarity to the Pd-catalyzed reactions. Herein, we report a summary of recent advances in intermolecular allylic C–H functionalization via group IX-metal π-allyl complexes. Mechanism-driven development of new catalysts is highlighted, and the potential for future developments is discussed. 

   more » « less
2. Nickel-catalyzed enantioselective vinylation of aryl 2-azaallyl anions

   https://doi.org/10.1039/D1SC00972A  

   Duan, Shengzu; Deng, Guogang; Zi, Yujin; Wu, Xiaomei; Tian, Xun; Liu, Zhengfen; Li, Minyan; Zhang, Hongbin; Yang, Xiaodong; Walsh, Patrick J. (May 2021, Chemical Science)

   null (Ed.)

   A unique enantioselective nickel-catalyzed vinylation of 2-azaallyl anions is advanced for the first time. This method affords diverse vinyl aryl methyl amines with high enantioselectivities, which are frequently occurring scaffolds in natural products and medications. This C–H functionalization method can also be extended to the synthesis of enantioenriched 1,3-diamine derivatives by employing suitably elaborated vinyl bromides. Key to the success of this process is the identification of a Ni/chiraphos catalyst system and a less reducing 2-azaallyl anion, all of which favor an anionic vinylation route over a background radical reaction. A telescoped gram scale synthesis and a product derivatization study confirmed the scalability and synthetic potential of this method. 

   more » « less
3. Ligand‐Controlled Direct γ‐C−H Arylation of Aldehydes

   https://doi.org/10.1002/anie.201913126  

   Li, Bijin; Lawrence, Brianna; Li, Guigen; Ge, Haibo (January 2020, Angewandte Chemie International Edition)

   Abstract The first example of Pd^II‐catalyzed γ‐C(sp³)−H functionalization of aliphatic and benzoheteroaryl aldehydes has been developed using a transient ligand and an external ligand, concurrently. A wide array of γ‐arylated aldehydes were readily accessed without preinstalling internal directing groups. The catalytic mechanism was studied by performing deuterium‐labelling experiments, which indicated that the γ‐C(sp³)−H bond cleavage is the rate‐limiting step during the reaction process. This reaction could be performed on a gram scale, and also demonstrated its potential application in the synthesis of new mechanofluorochromic materials with blue‐shifted mechanochromic properties. 

   more » « less
4. Recent Advances in Metal‐Catalyzed Functionalization of Indoles

   https://doi.org/10.1002/adsc.202100116  

   Urbina, Kelvin; Tresp, David; Sipps, Karli; Szostak, Michal (April 2021, Advanced Synthesis & Catalysis)

   Abstract Indole is one of the most important heterocycles in organic synthesis, natural products, and drug discovery. Recently, tremendous advances in the selective functionalization of indoles have been reported. Although the most important advances have been powered by transition metal catalysis, exceedingly useful methods in the absence of transition metals have also been reported. In this review, we provide an overview of functionalization reactions of indoles that have been published in the last years with a focus on the most recent advances, aims, and future trends. The review is organized by the positional selectivity and type of methods used for functionalization. In particular, we discuss major advances in transition‐metal‐catalyzed C−H functionalization at the classical C2/C3 positions, transition‐metal‐catalyzed C−H functionalization at the remote C4/C7 positions, transition‐metal‐catalyzed cross‐coupling, and transition‐metal‐free functionalization. magnified image 

   more » « less
5. Palladium-catalyzed direct asymmetric C–H bond functionalization enabled by the directing group strategy

   https://doi.org/10.1039/D0SC03052J  

   Yang, Ke; Song, Mengjie; Liu, Hao; Ge, Haibo (December 2020, Chemical Science)

   null (Ed.)

   In the past decade, selective C–C and C-heteroatom bond construction through palladium-catalyzed direct C–H bond functionalization has been extensively studied by employing a variety of directing groups. Within this category, direct asymmetric C(sp 2 )–H and C(sp 3 )–H activation for the construction of highly enantiomerically enriched skeletons still progressed at a slow pace. This minireview briefly introduces the major advances in the field for palladium-catalyzed direct asymmetric C–H bond functionalization via the directing group strategy. 

   more » « less