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2.
J Am Chem Soc ; 142(16): 7322-7327, 2020 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-32267146

RESUMO

The first copper-catalyzed atroposelective Michael-type addition between azonaphthalenes and arylboronic acids for the construction of biaryl atropisomers was established using a novel BINOL-derived phosphoramidite as a chiral ligand. A broad range of atropisomeric biaryls were obtained with good efficiency, and the practicality of this approach was verified by versatile transformations toward axially chiral ligands, catalysts, and other functional atropisomers. This set of catalytic systems successfully inhibited the routine 1,2-addition and promoted the formation of an aryl-aryl chiral axis. Meanwhile, this strategy bypassed the use of an oxidant as well as the harsh conditions normally necessary for transition-metal-mediated arene C-H coupling with arylboronic acids as an arylation counterpart, offering a straightforward alternative to access optically active biaryls.

3.
J Am Chem Soc ; 141(11): 4558-4563, 2019 03 20.
Artigo em Inglês | MEDLINE | ID: mdl-30835455

RESUMO

The first Pd(II)-catalyzed enantioselective alkynylation of unbiased methylene ß-C(sp3)-H bonds is reported. The readily accessible and tunable BINOL derivatives are used as chiral ligands in C-H activation for the first time. 3,3'-Fluorinated-BINOL proved crucial in determining both the reactivity and enantioselectivity. A wide range of carboxylic acid derivatives are well tolerated with high enantioselectivities (up to 96% ee). Mechanistic studies suggest that multiple ligands may participate in the stereodetermining C-H palladation step, and a chiral amplification effect is observed.

4.
Angew Chem Int Ed Engl ; 57(29): 9093-9097, 2018 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-29806879

RESUMO

Enantioselective functionalizations of unbiased methylene C(sp3 )-H bonds of linear systems by metal insertion are intrinsically challenging and remain a largely unsolved problem. Herein, we report a palladium(II)-catalyzed enantioselective arylation of unbiased methylene ß-C(sp3 )-H bonds enabled by the combination of a strongly coordinating bidentate PIP auxiliary with a monodentate chiral phosphoric acid (CPA). The synergistic effect between the PIP auxiliary and the non-C2 -symmetric CPA is crucial for effective stereocontrol. A broad range of aliphatic carboxylic acids and aryl bromides can be used, providing ß-arylated aliphatic carboxylic acid derivatives in high yields (up to 96 %) with good enantioselectivities (up to 95:5 e.r.). Notably, this reaction also represents the first palladium(II)-catalyzed enantioselective C-H activation with less reactive and cost-effective aryl bromides as the arylating reagents. Mechanistic studies suggest that a single CPA is involved in the stereodetermining C-H palladation step.

5.
Chem Commun (Camb) ; 53(74): 10287-10290, 2017 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-28868560

RESUMO

A highly selective nickel-catalyzed C-H trifluoroethylation of heteroarenes was developed with the assistance of a monodentate directing group. This protocol provides efficient access to various trifluoroethyl-substituted heteroarenes, including indoles, pyrroles, furans, and thiophenes, with commercially available CF3CH2I as an alkylation reagent. This robust catalytic procedure is scalable and tolerates a broad range of functional groups. Moreover, multifluoroalkylation of indoles is also viable.

6.
Angew Chem Int Ed Engl ; 55(44): 13859-13862, 2016 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-27678130

RESUMO

A general and practical PdII -catalyzed intermolecular silylation of primary and secondary C-H bonds of α-amino acids and simple aliphatic acids is reported. This method provides divergent and stereoselective access to a variety of optical pure ß-silyl-α-amino acids, which are useful for genetic technologies and proteomics. It can also be readily performed on a gram scale and the auxiliary can be easily removed with retention of configuration. The synthetic importance of this method is further demonstrated by the late-stage functionalization of biological small molecules, such as (-)-santonin and ß-cholic acid. Moreover, several key palladacycles were successfully isolated and characterized to elucidate the mechanism of this ß-C(sp3 )-H silylation process.


Assuntos
Aminoácidos/síntese química , Paládio/química , Silanos/síntese química , Aminoácidos/química , Catálise , Conformação Molecular , Silanos/química , Estereoisomerismo
7.
Org Lett ; 18(8): 1776-9, 2016 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-27023432

RESUMO

A mild Co(III)-catalyzed oxidative annulation of N-arylureas and internal alkynes has been developed. The use of less electrophilic ureas other than acetamides as directing groups is crucial for the reaction. A broad range of synthetically useful functional groups are compatible with this reaction, thus providing a new opportunity for the synthesis of diverse indoles.

8.
Org Lett ; 17(13): 3338-41, 2015 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-26102510

RESUMO

A copper/silver-mediated arylation of (hetero)aryl C-H bonds with 2-thiophenecarboxylic acids has been achieved. The protocol features a broad substrate scope and high functional group tolerance. Preliminary mechanistic studies indicate that a cascade protodecarboxylation/dehydrogenative coupling process is likely involved.

9.
Chem Commun (Camb) ; 51(58): 11650-3, 2015 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-26099578

RESUMO

Ni(II)-catalyzed dehydrative alkynylation of unactivated C(sp(2))-H bonds with terminal alkynes under atmospheric pressure of oxygen was developped. This reaction features the use of catalytic amounts of nickel as the catalyst and O2 as the sole oxidant, providing a user-friendly approach to the synthesis of aryl alkynes.


Assuntos
Alquinos/química , Níquel/química , Oxidantes/química , Oxigênio/química , Pressão Atmosférica , Catálise
10.
Chem Commun (Camb) ; 51(37): 7899-902, 2015 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-25857332

RESUMO

The first nickel-catalyzed alkenylation of unactivated C(sp(3))-H bonds with vinyl iodides is described. The catalytic system comprises an inexpensive and air-stable Ni(acac)2 as the catalyst and BINOL as the ligand, which is highly efficient for the alkenylation of ß-methyl C(sp(3))-H bonds of a broad range of aliphatic carboxamides. The resulting olefins can serve as versatile handles for further preparation. Additionally, we also demonstrated the synthesis of functionalized carboxamides bearing α-quaternary carbon centers from simple pivalamide via nickel-catalyzed sequential C(sp(3))-H bond functionalization.


Assuntos
Alcenos/síntese química , Alquinos/química , Naftóis/química , Níquel/química , Compostos Organometálicos/química , Alcenos/química , Catálise , Ligantes , Conformação Molecular , Compostos de Vinila/química
11.
Chem Commun (Camb) ; 51(34): 7341-4, 2015 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-25820073

RESUMO

The first nickel-catalyzed thiolation of unactivated C(sp(3))-H bonds with disulfides was described. This transformation uses (dppp)NiCl2 as a catalyst and BINOL as a ligand, which are efficient for the thiolation of ß-methyl C(sp(3))-H bonds of a broad range of aliphatic carboxamides. The reaction provides an efficient synthetic pathway to access diverse thioethers.

12.
Chem Commun (Camb) ; 51(29): 6388-91, 2015 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-25762446

RESUMO

A sustainable and simple catalytic system for the atom-economical alkynylation of benzamides with low nickel loadings is described. No organic or metallic oxidants and expensive ligands are required. A broad range of benzamides and bromoalkynes bearing various synthetically useful functional groups are compatible with this reaction. The versatility of this operationally simple protocol has been further demonstrated by the controllable mono- and di-alkynylation. Importantly, substrate/catalyst ratios of up to 200, and a turnover number of 196 were achieved, highlighting the potential of this protocol for synthetic applications.


Assuntos
Alquinos/química , Carbono/química , Hidrogênio/química , Níquel/química , Catálise , Química Verde
13.
Chem Commun (Camb) ; 51(19): 4069-72, 2015 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-25661824

RESUMO

A nickel-catalyzed thiolation of unactivated C(sp(2))-H bonds with disulfides employing the PIP directing group was described. This process uses a catalytic nickel catalyst and no metallic oxidants or cocatalysts are required. The reaction tolerates various important functional groups and heteroarenes, providing an efficient synthetic pathway to access diverse diaryl sulfides.

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