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1.
Chem Soc Rev ; 49(13): 4254-4272, 2020 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-32458919

RESUMO

Resource economy constitutes one of the key challenges for researchers and practitioners in academia and industries, in terms of rising demand for sustainable and green synthetic methodology. To achieve ideal levels of resource economy in molecular syntheses, novel avenues are required, which include, but are not limited to the use of naturally abundant, renewable feedstocks, solvents, metal catalysts, energy, and redox reagents. In this context, electrosyntheses create the unique possibility to replace stoichiometric amounts of oxidizing or reducing reagents as well as electron transfer events by electric current. Particularly, the merger of Earth-abundant 3d metal catalysis and electrooxidation has recently been recognized as an increasingly viable strategy to forge challenging C-C and C-heteroatom bonds for complex organic molecules in a sustainable fashion under mild reaction conditions. In this review, we highlight the key developments in 3d metallaelectrocatalysis in the context of resource economy in molecular syntheses until February 2020.

2.
Angew Chem Int Ed Engl ; 58(29): 9820-9825, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31075177

RESUMO

Visible-light-induced ruthenium catalysis has enabled remote C-H alkylations with excellent levels of position control under exceedingly mild conditions at room temperature. The metallaphotocatalysis occurred under exogenous-photosensitizer-free conditions and features an ample substrate scope. The robust nature of the photo-induced mild meta-C-H functionalization is reflected by the broad functional group tolerance, and the reaction can be carried out in an operationally simple manner, setting the stage for challenging secondary and tertiary meta-C-H alkylations by ruthenaphotoredox catalysis.

3.
Chem Rev ; 119(4): 2192-2452, 2019 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-30480438

RESUMO

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

4.
Chem Sci ; 9(18): 4203-4216, 2018 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-29780550

RESUMO

C4-decorated indoles feature in a plethora of bioactive and functional compounds of importance to natural product synthesis, material sciences, as well as crop protection and pharmaceutical industries. Traditionally, their syntheses largely involved harsh stoichiometric metalations and radical reactions. However, transition metal catalysed C-H activation has recently evolved into a powerful strategy for the late-stage diversification of indoles at the C4-H position. Modern photoredox, enzymatic and precious transition metal catalysis represent the key stimuli for developing challenging C-C and C-Het bond forming transformations under mild reaction conditions. Herein, we discuss the evolution and application of these methods for the step-economical transformations of otherwise inert C4-H bonds up to December 2017.

5.
J Am Chem Soc ; 139(47): 17015-17021, 2017 11 29.
Artigo em Inglês | MEDLINE | ID: mdl-29088912

RESUMO

An Fe(III)-promoted oxidative annulation reaction was developed for the synthesis of 1,2-naphthoquinones. A variety of substituted arylglyoxals and internal alkynes undergo the transformation in the presence of FeCl3 at room temperature to afford the 1,2-naphthoquinone products in good yields in a short reaction time. Interestingly, the products show unusual pseudomigration of the substituent on the arene ring of arylglyoxals. A possible mechanism involving Fe(III)-promoted formation of a vinyl cation from arylglyoxal and alkyne, electrophilic addition of the vinyl cation to the ipso carbon of the aryl group to give a spiral intermediate, and then migration of the keto carbon to the ortho carbon was proposed as key steps and verified using quantum mechanics.

6.
Chem Commun (Camb) ; 53(43): 5906-5909, 2017 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-28513650

RESUMO

Inexpensive copper catalysts enabled direct C-H chalcogenations at ambient temperature by means of photo-induced catalysis. The expedient copper catalysis set the stage for C-S and C-Se bond formation from readily accessible non-volatile elemental chalcogens. The photo-assisted copper catalysis manifold proved suitable for a wide range of substrates with good functional group tolerance and exhibited high catalytic efficacy even at a reaction temperature of 25 °C.

7.
ACS Appl Mater Interfaces ; 8(40): 27026-27034, 2016 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-27648600

RESUMO

We have successfully synthesized a series of blue thermally activated delayed fluorescence emitters, BPy-pC, BPy-pTC, BPy-p2C, and BPy-p3C, bearing a 4-benzoylpyridine core as the electron-accepting unit and carbazolyl, tert-butylcarbazolyl, dicarbazolyl, and tercarbazolyl groups as the electron-donating units, respectively. The density functional theory calculation shows that all of the compounds have their lowest unoccupied molecular orbitals on the benzoylpyridine moiety. However, the highest occupied molecular orbital (HOMO) of BPy-p3C is widely dispersed to the whole tercarbazolyl group, while the HOMOs of BPy-pC and BPy-pTC are mainly on the carbazolyl and extended to the phenyl ring. As a result, ΔEST is reduced from 0.29 eV for BPy-pC to 0.05 eV for BPy-p3C, and the organic light-emitting diodes using these materials as dopants emit blue light and their maximum external quantum efficiencies (EQEs) increase from 4.2% to 23.9% for BPy-pC and BPy-p3C, respectively. The EQE of the BPy-p3C-based device increases 2 times more than that of the BPy-pTC-based device without a significant change in the color coordinates.

8.
Org Lett ; 18(14): 3314-7, 2016 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-27357724

RESUMO

An efficient C-H activation method for the ortho alkynylation of aromatic N-methoxyamides with hypervalent iodine-alkyne reagent using a ruthenium catalyst is described. The reaction proceeds under mild reaction conditions with broad substrate scope. A possible catalytic cycle involving a ruthenium carboxylate assisted C-H bond cleavage is proposed from the preliminary mechanistic evidence.

9.
Angew Chem Int Ed Engl ; 55(13): 4308-11, 2016 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-26914532

RESUMO

A highly diastereoselective method for the synthesis of dihydroepoxybenzofluorenone derivatives from aromatic/vinylic amides and bicyclic alkenes is described. This new transformation proceeds through cobalt-catalyzed C-H activation and intramolecular nucleophilic addition to the amide functional group. Transition-metal-catalyzed C-H activation reactions of secondary amides with alkenes usually lead to [4+2] or [4+1] annulation; to the best of our knowledge, this is the first time that a [3+2] cycloaddition is described in this context. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. Mechanistic studies imply that the C-H bond cleavage may be the rate-limiting step.

10.
Chem Asian J ; 11(4): 448-60, 2016 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-26603577

RESUMO

Cationic N-heterocycles are an important class of organic compounds largely present in natural and bioactive molecules. They are widely used as fluorescent dyes for biological studies, as well as in spectroscopic and microscopic methods. These compounds are key intermediates in many natural and pharmaceutical syntheses. They are also a potential candidate for organic light-emitting diodes (OLEDs). Because of these useful applications, the development of new methods for the synthesis of cationic N-heterocycles has received a lot of attention. In particular, many C-H activation methodologies that realize high step- and atom-economies toward these compounds have been developed. In this review, recent advancements in the synthesis and applications of cationic N-heterocycles through C-H activation reactions are summarized. The new C-H activation reactions described in this review are preferred over their classical analogs.

11.
J Am Chem Soc ; 138(2): 628-34, 2016 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-26709617

RESUMO

Two benzoylpyridine-carbazole based fluorescence materials DCBPy and DTCBPy, bearing two carbazolyl and 4-(t-butyl)carbazolyl groups, respectively, at the meta and ortho carbons of the benzoyl ring, were synthesized. These molecules show very small ΔEST of 0.03 and 0.04 eV and transient PL characteristics indicating that they are thermally activated delayed fluorescence (TADF) materials. In addition, they show extremely different photoluminescent quantum yields in solution and in the solid state: in cyclohexane the value are 14 and 36%, but in the thin films, the value increase to 88.0 and 91.4%, respectively. The OLEDs using DCBPy and DTCBPy as dopants emit blue and green light with EQEs of 24.0 and 27.2%, respectively, and with low efficiency roll-off at practical brightness level. The crystal structure of DTCBPy reveals a substantial interaction between the ortho donor (carbazolyl) and acceptor (4-pyridylcarbonyl) unit. This interaction between donor and acceptor substituents likely play a key role to achieve very small ΔEST with high photoluminescence quantum yield.

12.
Org Lett ; 17(15): 3846-9, 2015 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-26208248

RESUMO

A novel method for the regio- and stereoselective synthesis of substituted 3-coumaranones from salicylaldehydes and allenes using a rhodium(III) catalyst has been developed. This procedure gives access to new 2-vinyl-substituted 3-coumaranone compounds. The method involves a Rh(III)-catalyzed aldehyde C-H activation and annulation reactions. Moreover, this Rh(III)-catalyzed [4 + 1] annulation reaction has been applied to 2-aminobenzaldehydes to afford 2,2-disubstituted 3-indolinones.


Assuntos
Alcadienos/química , Benzaldeídos/química , Cumarínicos/síntese química , Indóis/síntese química , Ródio/química , Catálise , Cumarínicos/química , Indóis/química , Estrutura Molecular , Estereoisomerismo
13.
Chemistry ; 21(25): 9198-203, 2015 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-25963039

RESUMO

A highly regio- and stereoselective synthesis of 3,3-disubstituted phthalides from aryl carboxylic acids and allenes using a rhodium(III) catalyst has been demonstrated. The reaction features broad functional group tolerance and provides a simple and straightforward route to the synthesis of various 3-vinyl-substituted phthalides. Furthermore, the catalytic reaction can also be applied to the synthesis of biologically active 5-vinyl-substituted 2-furanones from α,ß-unsaturated carboxylic acids and allenes. The reactions proceed through a carboxylate-assisted ortho-CH activation and [4+1] annulation. The preliminary mechanistic studies suggest that a CH cleavage is the rate-determining step.

14.
Acc Chem Res ; 48(4): 1194-206, 2015 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-25854540

RESUMO

Over the last three decades, transition-metal-catalyzed organic transformations have been shown to be extremely important in organic synthesis. However, most of the successful reactions are associated with noble metals, which are generally toxic, expensive, and less abundant. Therefore, we have focused on catalysis using the abundant first-row transition metals, specifically cobalt. In this Account, we demonstrate the potential of cobalt catalysis in organic synthesis as revealed by our research. We have developed many useful catalytic systems using cobalt complexes. Overall, they can be classified into several broad types of reactions, specifically [2 + 2 + 2] and [2 + 2] cycloadditions; enyne reductive coupling; reductive [3 + 2] cycloaddition of alkynes/allenes with enones; reductive coupling of alkyl iodides with alkenes; addition of organoboronic acids to alkynes, alkenes, or aldehydes; carbocyclization of o-iodoaryl ketones/aldehydes with alkynes/electron-deficient alkenes; coupling of thiols with aryl and alkyl halides; enyne coupling; and C-H bond activation. Reactions relying on π components, specifically cycloaddition, reductive coupling, and enyne coupling, mostly afford products with excellent stereo- and regioselectivity and superior atom economy. We believe that these cobalt-catalyzed π-component coupling reactions proceed through five-membered cobaltacyclic intermediates formed by the oxidative cyclometalation of two coordinated π bonds of the substrates to the low-valent cobalt species. The high regio- and stereoselectivity of these reactions are achieved as a result of the electronic and steric effects of the π components. Mostly, electron-withdrawing groups and bulkier groups attached to the π bonds prefer to be placed near the cobalt center of the cobaltacycle. Most of these transformations proceed through low-valent cobalt complexes, which are conveniently generated in situ from air-stable Co(II) salts by Zn- or Mn-mediated reduction. Overall, we have shown these reactions to be excellent substitutes for less desirable noble-metal systems. Recent successes in cobalt-catalyzed C-H activation have especially advanced the applicability of cobalt in this field. In addition to the more common low-valent-cobalt-catalyzed C-H activation reactions, an in situ-formed cobalt(III) five-membered complex with a 1,6-enyne effectively couples with aromatic ketones and esters through ortho C-H activation, opening a new window in this research area. Interestingly, this reaction proceeds under milder reaction conditions with broad substrate scope. Furthermore, many of the reactions we have developed are highly enantioselective, including enantioselective reductive coupling of enones and alkynes, addition of organoboronic acids to aldehydes, and the cyclization of 2-iodobenzoates with aldehydes. Overall, this Account demonstrates the versatility and utility of cobalt catalysis in organic synthesis.

15.
Org Lett ; 17(4): 924-7, 2015 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-25642795

RESUMO

A synthetic method for highly substituted pyridinium salts from the multicomponent reaction of vinyl ketones/aldehydes, amines, and alkynes using a rhodium catalyst is demonstrated. The catalytic reaction proceeds via an in situ generated imine-assisted Rh(III)-catalyzed vinylic C-H activation.

16.
Chem Asian J ; 10(4): 824-38, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25581838

RESUMO

Transition-metal-catalyzed C - H activation is considered to be an important tool in organic synthesis and has been accepted and widely used by chemists because it is straightforward, cost-effective, and environmentally friendly. A variety of functional groups have been used to direct metal complexes and achieve regioselective C - H activation. Most directing is achieved through the σ-bond coordination of functional groups to the metal catalyst, followed by ortho-selective C - H bond cleavage. However, recent work has demonstrated that π-coordinating functional groups can also assist in guiding metal complexes for site-selective C - H bond activation. This emerging approach significantly expands the scope of C - H activation reactions in organic synthesis. Herein, recent developments in this field are summarized.

17.
Org Biomol Chem ; 12(45): 9105-8, 2014 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-25313516

RESUMO

A new strategy for the synthesis of highly substituted benzofurans from meta-substituted hydroxybenzenes and alkynes via a rhodium(III)-catalyzed activation of a sterically hindered C-H bond is demonstrated. A possible mechanism involving dual directing group assisted ortho C-H bond activation is proposed.


Assuntos
Benzofuranos/síntese química , Ródio/química , Benzofuranos/química , Catálise , Ligação de Hidrogênio , Estrutura Molecular
18.
Org Lett ; 16(11): 2806-9, 2014 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-24814864

RESUMO

A nickel-catalyzed highly regioselective 1,4-addition reaction of boronic acids to dienones to form products with an all-carbon quaternary center is described. The 3-alkenyl group of dienones is the key for the reaction to proceed smoothly. A mechanism involving the coordination of the dienyl group to the nickel center is proposed.


Assuntos
Alcenos/química , Ácidos Borônicos/química , Carbono/química , Níquel/química , Catálise , Estrutura Molecular , Estereoisomerismo
19.
Chem Commun (Camb) ; 50(23): 3106-8, 2014 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-24519846

RESUMO

An efficient synthesis of highly substituted isoquinolinium salts from ketimines and alkynes via a Rh(III)-catalyzed C-H bond activation and annulation reaction is described.


Assuntos
Alquinos/química , Iminas/química , Isoquinolinas/síntese química , Nitrilos/química , Ródio/química , Sais/síntese química , Isoquinolinas/química , Sais/química
20.
Org Lett ; 15(22): 5750-3, 2013 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-24156564

RESUMO

An efficient and mechanistically interesting method for the synthesis of highly substituted isoquinolines by a Rh(III)-catalyzed hydrazone directed ortho C-H bond activation and annulation without an external oxidant is described. This reaction is accomplished via a C-C and C-N bond formation along with N-N bond cleavage.


Assuntos
Hidrazonas/química , Isoquinolinas/síntese química , Ródio/química , Catálise , Ligação de Hidrogênio , Isoquinolinas/química , Estrutura Molecular
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