Meta-Selective C–H Functionalization Using a Nitrile-Based Directing Group and Cleavable Si-Tether

Lee, Sunggi; Lee, Hyelee; Tan, Kian L.

doi:10.1021/ja4107034

Cited by 230 publications

(86 citation statements)

References 66 publications

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“…[24] Besides their easy synthesis as well as facile removal, the elongated SiÀCa nd SiÀOb onds permitted an optimal separation between the directing nitrile group and the aromatic reactant. [24] Besides their easy synthesis as well as facile removal, the elongated SiÀCa nd SiÀOb onds permitted an optimal separation between the directing nitrile group and the aromatic reactant.…”

Section: Silyl-bridged Directing Groupsmentioning

confidence: 99%

“…[33] With the help of as imilar 2-cyanophenol-derivatized template,t hey were able to achieve ah ighly regioselective meta-olefination of arange of aryl alcohols from adistal location of the directing group.I nt he presence of Pd(OAc) 2 as the catalyst, aw ide range of aryl alcohols,namely 3-phenylpropanols,2-phenoxyethanols,a nd 2-(phenylamino)ethanols,w ere succesfully olefinated at the meta-position with yields as high as 91 % (meta/others > 20:1; 86 a-g). [9,24] As will be discussed in the following sections,Y ua nd co-workers achieved the metaolefination of 2-phenylethyl alcohols by using aheterocyclicbased template. [11] Further theoretical calculations showed that the C-N-Ag angle played an important role in scaffolds with short linkers,w hereas the torsional strain resulting from the gauche conformation about the phenylethyl bond is crucial for longer linkers to obtain metaselectivity.Furthermore,the directing group can be removed by treatment with ceric ammonium nitrate (CAN) at room temperature (87!88).…”

Section: Angewandte Chemiementioning

confidence: 99%

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Accessing Remote meta‐ and para‐C(sp²)−H Bonds with Covalently Attached Directing Groups

et al. 2019

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Directing group assisted ortho‐C−H activation has been known for the last few decades. In contrast, extending the same approach to achieve activation of the distal meta‐ and para‐C−H bonds in aromatic molecules remained elusive for a long time. The main challenge is the conception of a macrocyclic transition state, which is needed to anchor the metal catalyst close to the target bond. Judicious modification of the chain length, the tether linkage, and the nature of the catalyst‐coordinating donor atom has led to a number of successful studies in the last few years. This Review compiles the significant achievements made in this field of both meta‐ and para‐selectivity using covalently attached directing groups, which are systematically classified on the basis of their mode of covalent attachment to the substrate as well as their chemical nature. This Review aims to create a more heuristic approach for recognizing the suitability of the directing groups for use in future organic transformations.

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Section: Silyl-bridged Directing Groupsmentioning

confidence: 99%

Section: Angewandte Chemiementioning

confidence: 99%

Accessing Remote meta‐ and para‐C(sp²)−H Bonds with Covalently Attached Directing Groups

et al. 2019

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“…Transformations reported by Hartwig, [7] Yu, [8] Tan, [9] Dong, [10] Zhao, [11] and us [12] demonstrated the feasibility of this concept in C–H functionalization. Specifically, a recent report from Zhao and coworkers [11b] demonstrated the Pd-catalyzed ortho -selective arylation to construct biaryls, using oximes as the surrogate species.…”

mentioning

confidence: 89%

Palladium(II)‐Catalyzed ortho‐Arylation of Aromatic Alcohols with a Readily Attachable and Cleavable Molecular Scaffold

Knight

Ferreira

2016

Chemistry A European J

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A palladium(II)-catalyzed C–H arylation process of alcohols has been developed. The strategy utilizes a novel quinoline-based hemiacetal scaffold that can direct the selective C–H bond functionalization. This reaction provides a useful method to construct biaryl compounds of benzyl alcohols in good to excellent yields. The new molecular scaffold can be readily attached, removed, and recovered.

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“…The groups of Tan 34 and Maiti 35 have independently developed the type-2 nitrile-based silyl DGs ( 22 and 23 , Scheme 2) for meta - and para -C–H functionalization of arenes, respectively, by merging Yu’s nitrile-based DG for a remote C–H functionalization 36 with our temporary silyl DG concept (Scheme 32). Both works feature a broad substrate scope, high degrees of regioselectivity, and the possibility to recover and reuse the silyl DG.…”

Section: C(sp2)–h Functionalization Via Silicon Tethersmentioning

confidence: 99%

Silicon-Tethered Strategies for C–H Functionalization Reactions

2017

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CONSPECTUS Selective and efficient functionalization of ubiquitous C–H bonds is the Holy Grail of organic synthesis. Most advances in this area rely on employment of strongly or weakly coordinating directing groups (DGs) which have proven effective for transition-metal-catalyzed functionalization of C(sp2)–H and C(sp3)–H bonds. Although most directing groups are important functionalities in their own right, in certain cases, the DGs become static entities that possess very little synthetic leverage. Moreover, some of the DGs employed are cumbersome or unpractical to remove, which precludes the use of this approach in synthesis. It is believed, that development of a set of easily installable and removable/modifiable DGs for C–H functionalization would add tremendous value to the growing area of directed functionalization, and hence would promote its use in synthesis and late-stage functionalization of complex molecules. In particular, silicon tethers have long provided leverage in organic synthesis as easily installable and removable/modifiable auxiliaries for a variety of processes, including radical transformations, cycloaddition reactions, and a number of TM-catalyzed methods, including ring-closing metathesis (RCM) and cross-coupling reactions. Employment of Si-tethers is highly attractive for several reasons: (1) they are easy to handle/synthesize and are relatively stable; (2) they utilize cheap and abundant silicon precursors; and (3) Si-tethers are easily installable and removable/modifiable. Hence, development of Si-tethers for C–H functionalization reactions is appealing not only from a practical but also from a synthetic standpoint, since the Si-tether can provide an additional handle for diversification of organic molecules post-C–H functionalization. Over the past few years, we developed a set of Si-tether approaches for C–H functionalization reactions. The developed Si-tethers can be categorized into four types: (Type-1) Si-tethers possessing a reacting group, where the reacting group is delivered to the site of functionalization; (Type-2) Si-tethers possessing a DG, designed for selective C(sp2)–H functionalization of arenes; (Type-3) reactive Si-tethers for C–H silylation of organic molecules; and finally, (Type-4) reactive Si-tethers containing a DG, developed for selective C–H silylation/hydroxylation of challenging C(sp3)–H bonds. In this Account, we outline our advances on the employment of silicon auxiliaries for directed C–H functionalization reactions. The discussion of the strategies for employment of different Si-tethers, functionalization/modification of silicon tethers, and the methodological developments on C–C, C–X, C–O, and C–Si bond forming reactions via silicon tethers will also be presented. While the work described herein presents a substantial advance for the area of C–H functionalization, challenges still remain. The use of noble metals are required for the C–H functionalization methods presented herein. Also, the need for stoichiometric use of high molecular weight silicon aux...

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Meta-Selective C–H Functionalization Using a Nitrile-Based Directing Group and Cleavable Si-Tether

Cited by 230 publications

References 66 publications

Accessing Remote meta‐ and para‐C(sp²)−H Bonds with Covalently Attached Directing Groups

Accessing Remote meta‐ and para‐C(sp²)−H Bonds with Covalently Attached Directing Groups

Palladium(II)‐Catalyzed ortho‐Arylation of Aromatic Alcohols with a Readily Attachable and Cleavable Molecular Scaffold

Silicon-Tethered Strategies for C–H Functionalization Reactions

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Meta-Selective C–H Functionalization Using a Nitrile-Based Directing Group and Cleavable Si-Tether

Cited by 230 publications

References 66 publications

Accessing Remote meta‐ and para‐C(sp2)−H Bonds with Covalently Attached Directing Groups

Accessing Remote meta‐ and para‐C(sp2)−H Bonds with Covalently Attached Directing Groups

Palladium(II)‐Catalyzed ortho‐Arylation of Aromatic Alcohols with a Readily Attachable and Cleavable Molecular Scaffold

Silicon-Tethered Strategies for C–H Functionalization Reactions

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Accessing Remote meta‐ and para‐C(sp²)−H Bonds with Covalently Attached Directing Groups

Accessing Remote meta‐ and para‐C(sp²)−H Bonds with Covalently Attached Directing Groups