Bidentate Directing Group Research Articles

Ni‐Catalyzed/mediated C−X (X=N, O, S) Bond Formation Chelation‐Assisted by Bidentate Directing Groups

AbstractRecently, transition‐metal‐catalyzed C−H functionalization has attracted significant attention due to its potential applications in different fields. Among different metals, nickel is regarded as a more sustainable 3d‐transition metal, which has been widely explored. Therefore, this review focuses on the recent advances in the field of nickel‐catalyzed C−H functionalization assisted with bidentate directing groups (DGs) to construct C−X (N, S, O) bond. The latest advancement in nickel catalysed C−X (N, S, O) bond are reviewed and covers literatures from 2015–2022. In addition, the substrate scope and limitations as well as partial mechanism are discussed.

Directed Palladium‐Catalyzed pseudo‐Anomeric C−H Functionalization of Glycal‐Type Substrates: Access to Unsymmetrical gem‐Diarylmethyl C‐Glycosides

Pd(II)-Catalyzed, bidentate directing group (BDG)-assisted C(sp2)−H functionalization of C2-amido glycals onto the anomeric position is described as a contemporary method for the construction of various unsymmetrical gem-diarylmethyl C-glycosides. Thanks to a bidentate amidoquinoline-type directing group, the insertion of diverse para-quinone methides (p-QMs) onto the pseudo-anomeric position of glycal substrates were executed in moderate to good yields. Further functionalization of the final product can be successfully demonstrated by known palladium-catalyzed cross-coupling reactions. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Overlooked potential of N,N-bidentate directing-groups in Ni-catalyzed C-H functionalization of benzamides.

The Ni-catalyzed reactions of benzamides with bicyclic alkenes were explored using DFT calculations. An unprecedented "N-H deprotonation circumvented" catalytic mechanism was proposed, over the more common N-H/C-H activation mechanism, in which (i) the circumvention of N-H deprotonation ensures the presence of N-H⋯O hydrogen bond interaction, thereby stabilizing the critical ortho-C-H functionalization TS; and (ii) the N-H moiety retention results in a weak N⋯Ni σ-coordination, which is flexible to the configurational conversion during the key alkene insertion. These overlooked aspects of the functionalized N,N-bidentate directing groups will aid the design of new related catalytic reactions.

Regio- and Stereoselective Functionalization Enabled by Bidentate Directing Groups.

Chelation-assisted C-H bond and alkene functionalization using bidentate directing groups offers an elegant and versatile approach to overcome regiocontrol issues by allowing the catalyst to come into close proximity with the targeted sites. In this personal account, we highlight our recent works in developing regio- and stereocontrolled functionalizations through transition-metal catalysis enabled by bidentate directing groups. We classify our results into two categories: (1) regioselective alkene functionalization using bidentate directing groups, and (2) asymmetric C-H functionalization using chiral bidentate directing groups. Furthermore, density functional theory studies to elucidate the origin of the regio- and stereoselectivity exerted by bidentate directing groups are discussed.

Ni-Catalyzed Intermolecular C(sp3)–H Amidation Tuned by Bidentate Directing Groups

We disclose herein a directing group-assisted nickel-catalyzed intermolecular C(sp3)–H amidation using organic azides as nitrene precursors. With the installation of an electronically tailored dire...

Traceless Bidentate Directing Group Assisted Cobalt-Catalyzed sp2-C-H Activation and [4 + 2]-Annulation Reaction with 1,3-Diynes.

An efficient cobalt-catalyzed [4 + 2] annulation of hydrazones and 1,3-diynes has been developed for the synthesis of 3-alkynylated isoquinolines engaging 2-aminopyridine as a traceless bidentate directing group. The strategy has been successfully extended for the synthesis of 3,3'-biisoquinoline moieties via both one-pot as well as sequential approaches. The utilization of a traceless bidentate directing group with an inexpensive and earth-abundant cobalt-catalyst under operationally simple reaction conditions makes the present transformation more valuable and appealing.

Investigations into the ligand steric and electronic effects of Ru-catalyzed C–H bond arylation directed by 8-aminoquinoline as a bidentate-directing group

In this study, we report an investigation into the steric (cone angle, θ) and electronic properties of ligands in Ru-catalyzed C–H arylation of aromatic benzamides bearing 8-aminoquinoline as an N,N’-bidentate-directing group. The study employs [RuCl2( p-cymene)]2 as a precatalyst, and a ligand, under study, as a cocatalyst. Various electronically and sterically different monodentate and bidentate phosphine ligands were examined. Other ligands such as phosphites and amines were also tested. The study reveals that while bidentate phosphines, phosphites, and aryl and alkyl amines were found to be ineffective, monodentate triarylphosphines represented by triphenylphosphine were found to be the most effective ligands in the Ru-catalyzed C–H arylation under the conditions specified. In addition, the study reveals that there is a correlation between the steric effects, cone angle (θ) and the reaction efficiency. Thus, for symmetrical phosphine ligands, as the cone angle increases, the yield of the CH arylation product gradually decreased. Moreover, the electronic properties of triarylphosphine ligands influenced the reaction as demonstrated by the decreased ability of electron-poor ligands to promote the reaction. The study also reveals a correlation between the electronic parameter, υCO, of the triarylphosphine ligand and the reaction efficiency. As the carbonyl stretching frequency increases, the reaction yield gradually decreased.

N-Amino-7-azaindole as the N,N'-Bidentate Directing Group: Ruthenium-Catalyzed Oxidative Annulation of N-(7-Azaindole)benzamides with Alkynes via C-H Bond Activation.

We report a new application of N-amino-7-azaindole as a new bidentate-directing group for [Ru(p-cymene)Cl2]2-catalyzed C(sp2)-H alkenylation/annulation of N-(1H-pyrrolo[2,3-b]pyridin-1-yl)benzamides with internal alkynes to afford N-isoquinolono-7-azaindole via the formation of C-C and C-N bonds. The reaction shows a wide range of substrate scope with different symmetrical and unsymmetrical alkynes, affording the desired product in good to excellent yields. In the case of unsymmetrical alkynes, a highly regioselective product was obtained, which was confirmed by single-crystal X-ray crystallography. A new ruthenium-4-methyl-N-(1H-pyrrolo[2,3-b]pyridin-1-yl)benzamide complex was isolated, and its structure was confirmed by single-crystal X-ray crystallography.

Pd(II)-Catalyzed Arylation and Intramolecular Amidation of γ-C(sp3)-H Bonds: En Route to Arylheteroarylmethane and Pyrrolidone Ring Annulated Furan/Thiophene Scaffolds.

We report the Pd(II)-catalyzed, bidentate directing group (BDG)-assisted arylation and successive arylation/intramolecular amidation of γ-C(sp3)-H bonds. The Pd(II)-catalyzed BDG-assisted C-H activation and functionalization of the β-C(sp3)-H bonds of carboxylic acids are well documented, but only a few reports are available that deal with the BDG-directed functionalization of the γ-C(sp3)-H bonds. Various 3-methylthiophene/furan-2-carboxamides (1a-e) were derived from their corresponding carboxylic acids and bidentate directing groups. These compounds were then used as substrates to investigate the arylation and successive arylation/intramolecular amidation of the γ-C(sp3)-H bonds. The γ-C(sp3)-H arylation arose from the Pd(II)-catalyzed reactions of these compounds with aryl iodides with reaction periods of 4-24 h (except a few reactions which required 36 or 48 h). Notably, these reactions led to the construction of various unsymmetrical diarylmethane scaffolds, such as thiophene/furan-based arylheteroarylmethanes (3-6). Prolonging the reaction period to 48-70 h led to successive γ-C(sp3)-H arylation/intramolecular amidation and the construction of both C-C and C-N bonds. Accordingly, these reactions led to the construction of new classes of pyrrolidone-ring annulated thiophene/furan-based heterocyclic scaffolds (e.g., 4,5-dihydro-6H-thieno[2,3-c]pyrrol-6-ones (8), 4,5-dihydro-6H-furo[2,3-c]pyrrol-6-ones (10), and 1-phenyl-1,2-dihydro-3H-benzo[4,5]thieno[2,3-c]pyrrol-3-ones (12)), and notably, compounds 8, 10, and 12 resemble the skeletons of 3-phenylisoindolin-1-ones.

Pd(II)-Catalyzed Bidentate Directing Group-Aided Chemoselective Acetoxylation of Remote ε-C(sp2)-H Bonds in Heteroaryl-Aryl-Based Biaryl Systems.

In this Article, we report our successful attempt on the Pd(II)-catalyzed, bidentate directing group-aided, chemoselective acetoxylation/substitution of remote ε-C(sp2)-H bonds using heteroaryl-aryl-based biaryl systems. While the bidentate directing group (BDG)-aided, C-H activation, and functionalization/acetoxylation of the β-, γ-, and δ-C-H bonds of the appropriate carboxamide systems were well documented, there exist only rare reports dealing with the C-H activation and functionalization of remote ε-C-H bonds of appropriate substrates. Especially, the BDG-aided chemoselective acetoxylation of the remote ε-C(sp2)-H bond over cyclization has not been explored well. Accordingly, in this work, the treatment of various picolinamides/oxalylamides/pyrazine-2-carboxamides 4/7/9/11, which were derived from the corresponding C-3 arylated furfurylamines or thiophen-2-ylmethanamines with PhI(OAc)2 in the presence of the Pd(OAc)2 catalyst, successfully afforded the corresponding ε-C-H acetoxylated products. The chemoselective acetoxylation of the ε-C-H bond was possible and facilitated by the biaryl substrate 4/7/9/11 and not by the biaryl substrate 2a.

ChemInform Abstract: Copper‐Catalyzed or ‐Mediated C—H Bond Functionalizations Assisted by Bidentate Directing Groups

AbstractReview: [55 refs.

Copper‐Catalyzed or ‐Mediated CH Bond Functionalizations Assisted by Bidentate Directing Groups

AbstractCopper salts, which are abundant, relatively inexpensive and possess low toxicity, have long been used as versatile catalysts for various reactions in organic synthesis. Recently, the development of Cu‐catalyzed or ‐mediated CH functionalization reactions has gained significant attention. Since the pioneering work of Daugulis on the introduction of 8‐aminoquinoline and picolinic acid auxiliaries as removable directing groups in transition metal‐catalyzed CH bond activations, the combination of copper salts with these bidentate directing groups has emerged as an innovative strategy for the construction of carbon‐carbon or carbon‐heteroatom bonds through CH bond cleavage. In addition to the 8‐aminoquinoline and picolinamide systems, several other bidentate directing groups including the 2‐aminophenyloxazoline group by Yu and Dai and the PIP system by Shi, have been developed as well. This review intends to cover most of the recent advances on copper‐catalyzed or ‐mediated direct sp2 and sp3 CH bond functionalizations assisted by these bidentate directing groups. The major achievements in this area are discussed and catalogued by the type of bonds formed (CC, CO, CN, CS, CP etc.). Special attention is paid to the reaction mechanisms. Selected examples of substrates are listed as well. In addition, a personal outlook is given at the end.magnified image

Understanding the Effects of Bidentate Directing Groups: A Unified Rationale for sp(2) and sp(3) C-H Bond Activations.

Bidentate directing group (DG) strategy is a promising way to achieve sp(2) and more inert sp(3) C-H bond activations in transition metal (TM) catalysis. In this work, we systematically explored the assisting effects exerted by bidentate DGs in the C-H bond activations. Through DFT calculations and well-defined comparative analysis, we for the first time unified the rationale of the reactivity promoted by bidentate DG in sp(2) and sp(3) C-H activations, which are generally consistent with available experimental discoveries about the C-H activation reactivity up to date. In addition to the general rationale of the reactivity, the assisting effects of several typical bidentate DGs were also quantitatively evaluated and compared to reveal their relative promoting ability for C-H activation reactivity. Finally, the effect of the ligating group charge and the position of the ligating group charge in bidentate DGs were also investigated, based on which new types of DGs were designed and proposed to be potentially effective in C-H activation. The deeper understanding and new insight about the bidentate DG strategy gained in this work would help to enhance its further experimental development in sp(2) and sp(3) C-H bond activations.

Transition-Metal-Catalyzed Arylation of Unactivated C(sp3)—H Bonds Assisted by Bidentate Directing Groups

近年来,过渡金属催化的惰性碳氢键官能团化受到广泛关注,然而,C(sp3)—H键由于低极性、高解离能和低选择性,其选择性活化尤为困难.综述了过渡金属催化的双齿导向基辅助的C(sp3)—H键芳基化的最新研究进展,主要探讨了不同过渡金属催化下芳基化反应的底物范围、反应机理和合成应用.

ChemInform Abstract: Ruthenium‐Catalyzed Direct Arylation of C—H Bonds in Aromatic Amides Containing a Bidentate Directing Group: Significant Electronic Effects on Arylation.

AbstractThe title reaction proceeds selectively at the less hindered C—H bonds of meta‐substituted aromatic amides (I).