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1.
Chem Commun (Camb) ; 57(99): 13542-13545, 2021 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-34841426

RESUMO

Although intramolecular hydroarylation is an attractive transformation of allylic aryl ethers, it has suffered from narrow substrate scope. We herein describe Ir/(S)-DTBM-SEGPHOS-catalyzed intramolecular hydroarylation of allylic aryl ethers. The reaction eliminates the structural requirement from the aryl group, affording 2,3-dihydrobenzofurans bearing a stereogenic carbon center at the C3 position with up to 99% enantiomeric excess.

2.
Chem Commun (Camb) ; 57(38): 4670-4673, 2021 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-33978003

RESUMO

Copper-catalyzed silafunctionalization of alkynes using a silylboronic ester as a silicon source has recently progressed rapidly. Generally, the reaction affords a product with cis-stereoselectivity. We herein describe trans-selective 1,2-addition of silylboronic esters to internal arylalkynes, which was promoted efficiently by the CuOt-Bu/RCy2P/NaOt-Bu catalysts. Moreover, we report a stereochemical switch to cis-addition in the reactions of Me2(i-PrO)Si-B(pin) in hydrocarbon solvents including cyclohexane.

3.
Org Lett ; 22(8): 2961-2966, 2020 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-32237751

RESUMO

A rhodium-catalyzed [4 + 2 + 1] cycloaddition involving 1,3-diene, alkyne, and silylene to afford silicon-containing seven-membered rings was established. In the presence of a rhodium catalyst bearing bis(diphenylphosphino)methane (DPPM), nona-1,3-dien-8-yne derivatives reacted efficiently at 80-110 °C with boryl(isopropoxy)silane or boryl(diethyamino)silane, which reacts as the synthetic equivalent of silylene, to afford 1-silacyclohepta-2,5-dienes (2,5-dihydro-1H-silepines). Regiodivergent and chemo- and stereoselective functionalization of the seven-membered nonconjugated diene was achieved by hydroboration mediated by Cs2CO3 or an iridium catalyst.

4.
Org Lett ; 21(24): 9812-9817, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31663767

RESUMO

4,4'-Bipyridyl worked as an organocatalyst for the reduction of nitroarenes by bis(neopentylglycolato)diboron (B2nep2), followed by hydrolysis to give the corresponding anilines. This reduction proceeded under aerobic conditions without any prepurification of substrates and reagents. We found broad functional group tolerance and compatibility for O- and N-protecting groups under the reaction conditions. The key in this catalytic system was the addition of B2nep2 to 4,4'-bipyridyl to form N,N'-bis[(neopentylglycolato)boryl]-4,4'-bipyridinylidene as a deoxygenating reagent of nitroarenes.

5.
Org Lett ; 21(6): 1649-1653, 2019 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-30835127

RESUMO

An alkene-alkyne-silylene [2 + 2 + 1] cycloaddition takes place in the rhodium-catalyzed reaction of 1,6-enynes with borylsilanes bearing an alkoxy group on the silicon atoms, which react as synthetic equivalents of silylene. The reaction proceeds efficiently in 1,2-dichloroethane at 80-110 °C in the presence of a rhodium catalyst bearing bis(diphenylphosphino)methane (DPPM) as a ligand to afford 1-silacyclopent-2-enes in good to high yields.

6.
Chem Asian J ; 13(17): 2414-2417, 2018 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-29733101

RESUMO

Suzuki-Miyaura coupling of nonbenzylic α-(acylamino)alkylboron compounds with aryl halides is established. A Pd/PCy2 Ph catalyst promotes the reaction efficiently at 145 °C. The reaction of enantioenriched α-(acylamino)alkylboron compounds affords chiral 1-arylalkylamides in high enantiospecificity and inversion of configuration.

7.
Angew Chem Int Ed Engl ; 56(45): 14272-14276, 2017 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-28948685

RESUMO

Highly enantioselective cycloisomerization of N-methylanilines, bearing o-alkenyl groups, into indolines is established. An iridium catalyst bearing a bidentate chiral diphosphine effectively promotes the intramolecular addition of the C(sp3 )-H bond across a carbon-carbon double bond in a highly enantioselective fashion. The reaction gives indolines bearing a quaternary stereogenic carbon center at the 3-position. The reaction mechanism involves rate-determining oxidative addition of the N-methyl C-H bond, followed by intramolecular carboiridation and subsequent reductive elimination.

8.
J Org Chem ; 82(6): 2943-2956, 2017 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-28185456

RESUMO

A conversion of trimethylsilylalkanes into the corresponding alcohols is established based on an iridium-catalyzed, chemoselective C(sp3)-H borylation of the methyl group on silicon. The (borylmethyl)silyl group formed by C(sp3)-H borylation is treated with H2O2/NaOH, and the resulting (hydroxymethyl)silyl group is converted into a hydroxyl group by Brook rearrangement, followed by oxidation of the resulting methoxysilyl group under Tamao conditions. An alternative route proceeding through the formylsilyl group formed from a (hydroxymethyl)silyl group by Swern oxidation is also established. The method is applicable to substituted trimethylsilylcycloalkanes and 1,1-dimethyl-1-silacyclopentane for conversion into the corresponding stereodefined cycloalkyl alcohols and 1,4-butanediol.

9.
Chemistry ; 22(30): 10415-9, 2016 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-27168516

RESUMO

Catalytic hydroalkylation of an alkyne with methyl ether was accomplished. Intramolecular addition of the C-H bond of a methoxy group in 1-methoxy-2-(arylethynyl)benzenes across a carbon-carbon triple bond took place efficiently either in toluene at 110 °C or in p-xylene at 135 °C in the presence of an iridium catalyst. The initial 5-exo cyclization products underwent double-bond migration during the reaction to give 3-(arylmethyl)benzofurans in high yields.

10.
J Am Chem Soc ; 137(8): 2852-5, 2015 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-25669237

RESUMO

A 4,4'-bipyridine-based catalyst system for diboration of pyrazine derivatives was established. The catalyst cycle consists of the following two steps: (1) reductive addition of the boron-boron bond of bis(pinacolato)diboron to 4,4'-bipyridine to form N,N'-diboryl-4,4'-bipyridinylidene and (2) oxidative boryl transfer from the intermediate to pyrazine to give N,N'-diboryl-1,4-dihydropyrazine with regeneration of 4,4'-bipyridine.

11.
Chem Commun (Camb) ; 50(48): 6333-6, 2014 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-24798257

RESUMO

The C(sp(3))-H bonds located on the methyl groups of an isopropyl group participate in iridium-catalysed C-H borylation with bis(pinacolato)diboron via a significant rate acceleration caused by a catalytic amount of t-BuOK.

12.
Org Lett ; 15(14): 3510-3, 2013 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-23829477

RESUMO

Reaction of N-alkylisoindoles with (bromoethynyl)triisopropylsilane afforded 1,3-bis(triisopropylsilylethynyl) isoindoles in high yields. The formal C-H alkynylation proceeds under transition-metal-free conditions through [4 + 2] cycloaddition of the pyrrole ring of isoindole with bromoalkyne followed by ring-opening of the product.

13.
J Am Chem Soc ; 134(42): 17416-9, 2012 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-23043232

RESUMO

A methyl group of methylchlorosilanes undergoes C-H borylation in an iridium-catalyzed reaction with bis(pinacolato)diboron in cyclohexane at 80 °C, giving (borylmethyl)chlorosilanes selectively.


Assuntos
Compostos de Boro/síntese química , Irídio/química , Compostos Organometálicos/química , Silanos/química , Silício/química , Compostos de Boro/química , Catálise , Estrutura Molecular
14.
Chem Commun (Camb) ; 48(68): 8571-3, 2012 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-22806333

RESUMO

Pyrazines and substituted pyrazines undergo addition of boron reagents having B-B, Si-B, and H-B bonds under transition-metal-free conditions, leading to high-yield synthesis of N-borylated 1,4-dihydropyrazines and 1,2,3,4-tetrahydropyrazine.

15.
J Am Chem Soc ; 134(27): 11092-5, 2012 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-22725612

RESUMO

The poly(quinoxaline-2,3-diyl)-based helically chiral phosphine ligands PQXphos exhibited high enantioselectivities up to 97% ee in palladium-catalyzed desymmetrization of meso-1,2-dialkylsubstituted-3-methylenecyclopropanes through silaborative cleavage of the C-C bond. The observed enantioselectivities were higher than those obtained with 2-diarylphosphino-1,1'-binaphthyl in our original report. Remarkable rate enhancement was also observed with a series of PQXphos in comparison with the corresponding low-molecular weight ligands.

16.
J Am Chem Soc ; 134(8): 3699-702, 2012 Feb 29.
Artigo em Inglês | MEDLINE | ID: mdl-22320932

RESUMO

Pyridine undergoes addition of pinacolborane at 50 °C in the presence of a rhodium catalyst, giving N-boryl-1,2-dihydropyridine in a high yield. The selective 1,2-hydroboration also takes place in the reactions of substituted pyridines. In the reaction of 3-substituted pyridines, 3-substituted N-boryl-1,2-dihydropyridines are formed regioselectively.


Assuntos
Compostos Organometálicos/química , Piridinas/química , Piridinas/síntese química , Ródio/química , Catálise , Estrutura Molecular , Estereoisomerismo
17.
J Am Chem Soc ; 133(51): 20738-41, 2011 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-22129167

RESUMO

The stereochemical course of the stereospecific Suzuki-Miyaura coupling of enantioenriched α-(acetylamino)benzylboronic esters with aryl bromides can be switched by the choice of acidic additives in the presence of a Pd/XPhos catalyst system. Highly enantiospecific, invertive C-C bond formation takes place with the use of phenol as an additive. In contrast, high enantiospecificity for retention of configuration is attained in the presence of Zr(Oi-Pr)(4)·i-PrOH as an additive.

18.
Angew Chem Int Ed Engl ; 50(52): 12501-4, 2011 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-22072495

RESUMO

Double take: ß-Borylallylsilanes have been synthesized by the regioselective silaboration of terminal alkynes followed by palladium-catalyzed double-bond migration of the resulting ß-borylalkenylsilanes. The stereoselectivity of the double-bond migration can be controlled by additives, thus leading to the stereocomplementary synthesis of (E)- and (Z)-ß-borylallylsilanes.


Assuntos
Alcinos/química , Compostos de Boro/síntese química , Silanos/síntese química , Compostos de Boro/química , Estrutura Molecular , Silanos/química , Estereoisomerismo
19.
J Am Chem Soc ; 133(19): 7324-7, 2011 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-21510608

RESUMO

The addition of silylboronic esters to pyridine takes place in toluene at 50 °C in the presence of a palladium catalyst to give N-boryl-4-silyl-1,4-dihydropyridines in high yield. The regioselective 1,4-silaboration also proceeds in the reaction of 2-picoline and 3-substituted pyridines, whereas 4-substituted pyridines undergo 1,2-silaboration to give N-boryl-2-silyl-1,2-dihydropyridines regioselectively.

20.
Org Lett ; 13(5): 1238-41, 2011 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-21275390

RESUMO

A one-pot conversion of isoindolines to 1-arylisoindoles was established from palladium-catalyzed cascade C-H transformations, that is, the dehydrogenation of isoindolines to give isoindoles, with subsequent C-H arylation of the isoindoles.


Assuntos
Isoindóis/química , Isoindóis/síntese química , Paládio/química , Catálise , Estrutura Molecular , Oxirredução
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