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1.
Org Lett ; 25(15): 2674-2679, 2023 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-37040108

RESUMO

The construction of all-carbon quaternary centers in small-ring systems is important but challenging in organic synthesis. Herein, by taking gem-difluorocyclopropyl bromides (DFCBs) as a type of general and versatile building block, we developed a practical method for building all-carbon quaternary centers in gem-difluorinated cyclopropanes (DFCs). The reaction relies on the involvement of a gem-difluorocyclopropyl radical intermediate, which can couple with a wide range of nucleophiles under copper catalysis.

2.
Org Lett ; 24(33): 6176-6181, 2022 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-35951978

RESUMO

Herein, we report an effective method to offer chiral gem-difluorinated cyclopropanes containing an all-carbon quaternary stereocenter by rhodium-catalyzed stereoablative kinetic resolution. The activation of a sterically hindered all-carbon quaternary C-C bond through oxidative addition with a chiral rhodium complex is proposed as the enantiodetermining step. A wide range of gem-difluorinated cyclopropanes can be obtained with excellent ee values (ee = 87% to >99.9%), which are demonstrated to be useful chiral fluorine-containing building blocks by a series of postfunctionalizations.


Assuntos
Ródio , Carbono/química , Catálise , Ciclopropanos/química , Estrutura Molecular , Ródio/química , Estereoisomerismo
3.
Chem Commun (Camb) ; 56(37): 5002-5005, 2020 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-32239072

RESUMO

Ring-opening iodination or bromination of unstrained cycloalkanols with NaI or NaBr and PhI(OAc)2 under visible light irradiation is developed. In this protocol the concentration of I2 is modulated through the generation of triiodide (I3-), thus significantly avoiding undesired side reactions. The reaction is under mild conditions and has a wide substrate scope, thus providing a practically useful method for accessing ω-iodo or ω-bromoketones.

4.
Chemistry ; 25(38): 8992-8995, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-31066949

RESUMO

The alkoxy radicals that are derived from cyclic hemiacetals have been generated through the visible-light-promoted reaction of the corresponding N-alkoxyphthalimides with Hantzsch ester as the reductant. The alkoxy radicals subsequently undergo ß-scission of the C-C bond to generate carbon-centered radicals, which are trapped by alkynyl-, alkenyl-, or allylsulfones.

5.
Chem Commun (Camb) ; 55(28): 4047-4050, 2019 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-30869685

RESUMO

We report herein an alkenylation of benzylic C(sp3)-H bonds with diazo compounds via carbon cation intermediates with DDQ as the oxidant in the presence of a catalytic amount of Fe(ii). Diphenylmethane, toluene, benzyl methyl sulfide and their derivatives could be applied as substrates to afford the tetra-substituted olefin products, which may serve as useful building blocks in organic synthesis.

6.
Nat Commun ; 8(1): 238, 2017 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-28798314

RESUMO

Metal-catalyzed cross-couplings provide powerful, concise, and accurate methods to construct carbon-carbon bonds from organohalides and organometallic reagents. Recent developments extended cross-couplings to reactions where one of the two partners connects with an aryl or alkyl carbon-hydrogen bond. From an economic and environmental point of view, oxidative couplings between two carbon-hydrogen bonds would be ideal. Oxidative coupling between phenyl and "inert" alkyl carbon-hydrogen bonds still awaits realization. It is very difficult to develop successful strategies for oxidative coupling of two carbon-hydrogen bonds owning different chemical properties. This article provides a solution to this challenge in a convenient preparation of dihydrobenzofurans from substituted phenyl alkyl ethers. For the phenyl carbon-hydrogen bond activation, our choice falls on the carboxylic acid fragment to form the palladacycle as a key intermediate. Through careful manipulation of an additional ligand, the second "inert" alkyl carbon-hydrogen bond activation takes place to facilitate the formation of structurally diversified dihydrobenzofurans.Cross-dehydrogenative coupling is finding increasing application in synthesis, but coupling two chemically distinct sites remains a challenge. Here, the authors report an oxidative coupling between sp 2 and sp 3 carbons by sequentially activating the more active aryl site followed by the alkyl position.

7.
Org Lett ; 18(6): 1238-41, 2016 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-26950017

RESUMO

A chlorobenzylation of terminal alkynes through Fe(II)-promoted benzylic C(sp(3))-H bond functionalization in the presence of NCS as a chloride source was developed. Compared with previous methods to prepare polysubstituted alkenyl halides, the presented procedure provides an efficient alternative with high atom and step economy under mild conditions. The transformation was established to proceed through a single-electron transfer (SET) process with benzyl cations as key intermediates.

8.
Chem Commun (Camb) ; 51(22): 4599-602, 2015 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-25687354

RESUMO

The sequential construction of diversified multifunctionalized thiazole derivatives through Pd-catalyzed regioselective C-H alkenylation has been accomplished. This versatile approach provides the diversified thiazole derivatives featuring orthogonal substitution patterns at the C-2, C-4 and C-5 positions from mono-substituted (2- or 4-substituted) thiazole derivatives or even more challenging simple thiazole.


Assuntos
Tiazóis/síntese química , Catálise , Estrutura Molecular , Compostos Organometálicos/química , Paládio/química , Estereoisomerismo , Tiazóis/química
9.
Chem Asian J ; 10(4): 840-3, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25605476

RESUMO

Biaryl skeletons were directly constructed via palladium-catalyzed ortho-arylation of N,N-dimethyl benzylamine with aryl boronic acids with high efficiency and high regioselectivity under open-flask conditions. The N,N-dimethylaminomethyl group was first applied as a directing group in such an oxidative coupling. Various substrates proved to be efficient coupling partners, furnishing the corresponding ortho-monoarylated or -diarylated arenes in moderate to good yields under mild conditions.


Assuntos
Ácidos Borônicos/química , Hidrocarbonetos/química , Paládio/química , Catálise , Ligação de Hidrogênio , Estrutura Molecular , Oxirredução
10.
Angew Chem Int Ed Engl ; 53(19): 4945-9, 2014 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-24706602

RESUMO

3,4-Dihydroquinolinones were synthesized by the palladium-catalyzed, oxidative-addition-initiated activation and arylation of inert C(sp(3) )H bonds. Pd(OAc)2 and P(o-tol)3 were used as the catalyst and ligand, respectively, to improve the efficiency of the reaction. A further advantage of this reaction is that it could be performed in air. A relatively rare seven-membered palladacycle was proposed as a key intermediate of the catalytic cycle.


Assuntos
Paládio/química , Quinolonas/química , Catálise
11.
Org Lett ; 15(22): 5774-7, 2013 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-24175690

RESUMO

An efficient regioselective arylation of thiazole derivatives via Pd-catalyzed C-H activation is reported. The transformation was hypothesized through a Pd(0/II) catalytic cycle in the absence of special ligand sets. This method provided an efficient process to direct arylation of thiazoles at the 5-position.


Assuntos
Paládio/química , Tiazóis/química , Catálise , Ligantes , Estrutura Molecular , Estereoisomerismo
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