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1.
Chemistry ; 25(39): 9174-9179, 2019 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-31050831

RESUMO

Herein, we report on the use a biohybrid catalyst consisting of palladium nanoparticles immobilized on cross-linked enzyme aggregates of lipase B of Candida antarctica (CalB CLEA) for the dynamic kinetic resolution (DKR) of benzylic amines. A set of amines were demonstrated to undergo an efficient DKR and the recyclability of the catalysts was studied. Extensive efforts to further elucidate the structure of the catalyst are presented.

2.
Chemistry ; 25(1): 210-215, 2019 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-30307089

RESUMO

A highly selective and efficient oxidative carbocyclization/borylation of enallenols catalyzed by palladium immobilized on amino-functionalized siliceous mesocellular foam (Pd-AmP-MCF) was developed for diastereoselective cyclobutenol synthesis. The heterogeneous palladium catalyst can be recovered and recycled without any observed loss of activity or selectivity. The high diastereoselectivity of the reaction is proposed to originate from a directing effect of the enallenol hydroxyl group. Optically pure cyclobutenol synthesis was achieved by the heterogeneous strategy by using chiral enallenol obtained from kinetic resolution.

3.
J Am Chem Soc ; 140(44): 14604-14608, 2018 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-30358399

RESUMO

A palladium-catalyzed oxidative tandem process of enallenols was accomplished within a homogeneous/heterogeneous catalysis manifold, setting the stage for the highly chemodivergent and diastereoselective synthesis of γ-lactones and γ-lactams under mild conditions.

4.
Chemistry ; 23(52): 12886-12891, 2017 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-28736879

RESUMO

Herein, we report on the utilization of a heterogeneous catalyst, consisting of Pd nanoparticles supported on a siliceous mesocellular foam (Pd0 -AmP-MCF), for the synthesis of heterocycles. Reaction of o-iodophenols and protected o-iodoanilines with acetylenes in the presence of a Pd nanocatalyst produced 2-substituted benzofurans and indoles, respectively. In general, the catalytic protocol afforded the desired products in good to excellent yields under mild reaction conditions without the addition of ligands. Moreover, the structure of the reported Pd nanocatalyst was further elucidated with extended X-ray absorption fine-structure spectroscopy, and it was proven that the catalyst could be recycled multiple times without significant loss of activity.

5.
Chemistry ; 23(5): 1048-1051, 2017 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-28005307

RESUMO

Herein, we report on a metalloenzymatic dynamic kinetic resolution of sec-alcohols employing an iron-based racemization catalyst together with a lipase. The iron catalyst was evaluated in racemization and then used in dynamic kinetic resolution of a number of sec-alcohols to give enantiomerically pure products in good to high yields. The iron catalyst is air and moisture stable and is readily accessible.

6.
Chemistry ; 22(33): 11583-6, 2016 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-27311070

RESUMO

Fe and Ru pincer-type catalysts are used for the racemization of benzylic alcohols. Racemization with the Fe catalyst was achieved within 30 minutes under mild reaction conditions, with a catalyst loading as low as 2 mol %. This reaction constitutes the first example of an iron-catalyzed racemization of an alcohol. The efficiency for racemization of the Fe catalyst and its Ru analogue was evaluated for a wide range of sec-benzylic alcohols. The commercially available Ru complex proved to be highly robust and even tolerated the presence of water in the reaction mixture.

7.
Chemistry ; 21(15): 5909-15, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25777800

RESUMO

Herein, we describe the use of Pd nanoparticles immobilized on an amino-functionalized siliceous mesocellular foam for the catalytic oxidation of H2O. The Pd nanocatalyst proved to be capable of mediating the four-electron oxidation of H2O to O2, both chemically and photochemically. The Pd nanocatalyst is easy to prepare and shows high chemical stability, low leaching, and recyclability. Together with its promising catalytic activity, these features make the Pd nanocatalyst of potential interest for future sustainable solar-fuel production.

8.
Angew Chem Int Ed Engl ; 54(17): 5122-6, 2015 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-25728614

RESUMO

Herein, a practical and mild method for the deoxygenation of a wide range of benzylic aldehydes and ketones is described, which utilizes heterogeneous Pd/C as the catalyst together with the green hydride source, polymethylhydrosiloxane. The developed catalytic protocol is scalable and robust, as exemplified by the deoxygenation of ethyl vanillin, which was performed on a 30 mmol scale in an open-to-air setup using only 0.085 mol % Pd/C catalyst to furnish the corresponding deoxygenated product in 93 % yield within 3 hours at room temperature. Furthermore, the Pd/C catalyst was shown to be recyclable up to 6 times without any observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions.


Assuntos
Aldeídos/química , Carbono/química , Cetonas/química , Paládio/química , Substâncias Redutoras/química , Siloxanas/química , Benzaldeídos/química , Catálise , Espectroscopia de Ressonância Magnética , Oxirredução , Temperatura Ambiente
9.
Chemistry ; 20(20): 5885-9, 2014 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-24687938

RESUMO

A highly dispersed nanopalladium catalyst supported on mesocellular foam (MCF), was successfully used in the heterogeneous catalysis of aminocarbonylation reactions. During the preliminary evaluation of this catalyst it was discovered that the supported palladium nanoparticles exhibited a "release and catch" effect, meaning that a minor amount of the heterogeneous palladium became soluble and catalyzed the reaction, after which it re-deposited onto the support.


Assuntos
Hidrocarbonetos Aromáticos/química , Iodetos/química , Nanopartículas Metálicas/química , Paládio/química , Amidas/química , Aminação , Aminas/química , Catálise
10.
J Org Chem ; 79(9): 3747-51, 2014 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-24724828

RESUMO

A catalyst consisting of palladium nanoparticles supported on amino-functionalized siliceous mesocellular foam (Pd-AmP-MCF) was used in chemoenzymatic dynamic kinetic resolution (DKR) to convert primary amines to amides in high yields and excellent ee's. The efficiency of the nanocatalyst at temperatures below 70 °C enables reaction conditions that are more suitable for enzymes. In the present study, this is exemplified by subjecting 1-phenylethylamine (1a) and analogous benzylic amines to DKR reactions using two commercially available lipases, Novozyme-435 (Candida antartica Lipase B) and Amano Lipase PS-C1 (lipase from Burkholderia cepacia) as biocatalysts. The latter enzyme has not previously been used in the DKR of amines because of its low stability at temperatures over 60 °C. The viability of the heterogeneous Pd-AmP-MCF was further demonstrated in a recycling study, which shows that the catalyst can be reused up to five times.


Assuntos
Aminas/química , Lipase/química , Nanopartículas Metálicas/química , Paládio/química , Termodinâmica , Aminas/metabolismo , Burkholderia cepacia/enzimologia , Candida/enzimologia , Catálise , Cinética , Lipase/metabolismo , Modelos Moleculares , Conformação Molecular , Paládio/metabolismo
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