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1.
Org Lett ; 21(9): 3422-3426, 2019 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-31012589

RESUMO

A highly efficient and straightforward synthesis of diversely substituted coumarins from ynamides and salicylaldehydes in the presence of Zn(II) catalyst has been developed. The sulfonamide moiety of ynamides was successfully recycled in this process, serving as an effective traceless directing group for high regioselectivity in the bond-forming event. The advantages of this protocol are good functional group tolerance, broad substrate scope, simple and high-yielding reaction, recovery/reuse of the sulfonamides, low catalyst loading of inexpensive catalyst, and, by these merits, a more cost-effective and greener process.

2.
Org Lett ; 20(24): 7869-7874, 2018 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-30511868

RESUMO

Regio- and stereoselective synthesis of ( E)-3-arylmethyleneisoindolin-1-ones via Pd(II)/Cu(II)-catalyzed one-pot C-C/C-N bond forming sequence between amides and styrenes is reported. This method provides facile and rapid access to a diverse range of such compounds using readily available starting materials under mild aerobic conditions with good functional group tolerance and high selectivity and efficiency. Further elaboration of the products obtained from this process enabled very short and efficient syntheses of aristolactam and indoloisoquinolinone alkaloids.

3.
Angew Chem Int Ed Engl ; 56(23): 6636-6640, 2017 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-28464374

RESUMO

A Pd-catalyzed intermolecular oxidative annulation between N-Ts-anilines and styrenes was developed. This method offers a straightforward and robust approach to a wide range of 3-arylindoles using readily available starting materials with good functional-group tolerance and high regioselectivity and efficiency. Further elaboration of the products obtained from this process provided access to highly functionalized and structurally diverse indoles, for example, 3-(indol-3-yl)carbazoles, 1,9-dihydropyrrolo-[2,3-b]carbazoles, and 3'-aryl-3,5'-biindoles.

4.
Org Lett ; 18(23): 6140-6143, 2016 12 02.
Artigo em Inglês | MEDLINE | ID: mdl-27934371

RESUMO

A simple and facile one-pot reaction has been developed to afford a diverse range of N,N'-disubstituted benzimidazolones and imidazopyridinones containing two differently substituted N atoms. A cooperative Pd(II)/Ag(I) system promotes the sequential addition/intramolecular C-H amidation reaction of (hetero)aromatic amines and isocyanates, leading to the formation of two C-N bonds. A mechanism involving radical intermediates generated by single-electron transfer (SET) in the presence of a Ag2CO3 oxidant and Pd(OAc)2 Lewis acid is proposed. This protocol offers an operationally easy, simple, and robust approach with the use of readily available starting materials, good functional group tolerance, and high efficiency.


Assuntos
Aminas/química , Isocianatos/química , Paládio/química , Prata/química , Ureia/síntese química , Estrutura Molecular , Ureia/análogos & derivados , Ureia/química
5.
Org Lett ; 18(21): 5728-5731, 2016 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-27775364

RESUMO

A highly efficient and facile metal-free, one-pot reaction has been developed to afford diversely substituted N-arylbenzimidazoles through chemoselective in situ generation of N,N'-diarylamidines from arenediazonium salts, nitriles, and free anilines. The advantages of this protocol consist of the operationally easy and simple one-pot procedure under metal-free and mild conditions, the direct use of inexpensive and commercially available chemicals, and thus, a cost-effective and greener process.

6.
Org Biomol Chem ; 14(7): 2200-4, 2016 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-26804765

RESUMO

A highly regioselective synthesis of 3-arylindoles by using the cooperative FeCl3/DDQ system has been developed. This new protocol represents an attractive route for the synthesis of 3-arylindoles from readily accessible non-indole precursors, ß-aryl-substituted 2-styrylanilines, using an inexpensive catalyst and oxidant. Noteworthy is the unique synergetic and synergistic effect of FeCl3 and DDQ on the 1,2-aryl migratory process.

7.
Org Biomol Chem ; 13(16): 4652-6, 2015 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-25793456

RESUMO

Inspired by the Hegedus aza-Wacker indole synthesis, we were intrigued with the fate of the aminopalladation intermediate if syn ß-hydrogen is made inaccessible or unavailable. In contrast to our previously reported ß-carbon elimination, cyclization of a variety of 2-alkenylaniline substrates under electrophilic palladium conditions unexpectedly afforded C3-substituted indoles. This unusual 1,2-migratory process was found to be operative across a variety of substrates with predictable migratory aptitude. A mechanistic proposal was put forward to rationalize the observed substrate dependence, and this unexpected finding could provide an opportunity for other related processes.

8.
Org Lett ; 16(14): 3720-3, 2014 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-24988548

RESUMO

An effective metal-free C-H amination of N-Ts-2-alkenylanilines by using DDQ as an oxidant has been developed to afford a diverse range of substituted indoles. This protocol is operationally simple and robust, obviates the need of expensive transition-metal catalysts, and offers a broad substrate scope. A mechanism involving a radical cation generated by SET and a migratorial process via a phenonium ion intermediate is proposed.


Assuntos
Indóis/síntese química , Aminação , Catálise , Técnicas de Química Combinatória , Indóis/química , Estrutura Molecular
9.
Org Biomol Chem ; 12(15): 2388-93, 2014 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-24595463

RESUMO

An efficient NHC-catalyzed domino oxidation/oxa-Michael addition reaction of 2-alkenylbenzaldehydes has been developed to afford 3-substituted phthalides bearing a C3-stereogenic center with a broad substrate scope and wide functional group tolerance. The preliminary results of the asymmetric process have been provided as well.


Assuntos
Benzofuranos/química , Benzofuranos/síntese química , Compostos Heterocíclicos/química , Metano/análogos & derivados , Catálise , Ciclização , Metano/química , Oxirredução
10.
Org Lett ; 16(3): 1028-31, 2014 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-24460222

RESUMO

It is demonstrated that two organocatalysts, achiral NHC and chiral bifunctional cinchonine, are mutually compatible and operating concurrently and effectively to promote the asymmetric domino oxidation/oxa-Michael addition reaction. This protocol allowed access to both enantiomers of a product by using two natural, inexpensive pseudoenantiomeric cinchona alkaloids, cinchonine and cinchonidine, as well as to phthalides containing a chiral quaternary carbon center in good enantioselectivities.

11.
Chemistry ; 18(31): 9452-74, 2012 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-22736530

RESUMO

The recent advent of transition-metal mediated C-H activation is revolutionizing the synthetic field and gradually infusing a "C-H activation mind-set" in both students and practitioners of organic synthesis. As a powerful testament of this emerging synthetic tool, applications of C-H activation in the context of total synthesis of complex natural products are beginning to blossom. Herein, recently completed total syntheses showcasing creative and ingenious incorporation of C-H activation as a strategic manoeuver are compared with their "non-C-H activation" counterparts, illuminating a new paradigm in strategic synthetic design.


Assuntos
Produtos Biológicos/síntese química , Produtos Biológicos/química , Catálise , Estrutura Molecular
12.
J Am Chem Soc ; 134(28): 11308-11, 2012 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-22721172

RESUMO

A Pd(II)-catalyzed reaction engaging alkenyl ß-keto esters is reported that leads to the formation of 1-naphthols and an unexpected generation of arylpalladium(II) species. Interception of the in situ generated arylpalladium(II) species in a Mizoroki-Heck reaction, together with additional mechanistic studies, provided strong evidence in support of the first aromatization-driven ß-carbon elimination process. A single Pd catalyst served to promote a series of both C-C bond forming and cleavage events in an unprecedented manner.

13.
J Org Chem ; 76(17): 7204-15, 2011 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-21780754

RESUMO

Au(I)-catalyzed cyclization of alkenyl carbonyl compounds leading to a variety of substituted naphthalenes has been developed. This process exploits a dual function of the Au(I) catalyst: (1) the oxophilic nature of the Au(I) catalyst, counterintuitive to the π-acidic reactivities generally associated with Au catalysts, and (2) olefin isomerization supported by the outcome of isotope scrambling experiments. It cannot be completely excluded that TfOH is a true operative catalyst in this protocol. In view of the practicality, the unnecessity of isomerically pure starting material in this reaction is particularly attractive and valuable.


Assuntos
Ouro/química , Naftalenos/síntese química , Catálise , Ciclização , Estrutura Molecular , Naftalenos/química
14.
Org Lett ; 13(14): 3738-41, 2011 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-21671638

RESUMO

A Pd-catalyzed oxidative C-H amination of N-Ts-2-arylanilines under ambient temperature using Oxone as an inexpensive, safe, and easy-to-handle oxidant has been developed. This process represents a green and practical method for the facile construction of carbazoles with a broad substrate scope and wide functional group tolerance.


Assuntos
Carbazóis/síntese química , Paládio/química , Aminação , Carbazóis/química , Catálise , Estrutura Molecular , Oxirredução
15.
Org Lett ; 13(9): 2228-31, 2011 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-21446687

RESUMO

An NHC-catalyzed, regio- and stereoselective oxidative cyclization of o-alkynylbenzaldehydes bearing an unactivated alkyne moiety as an internal electrophile has been developed to afford phthalides and isocoumarins. A single organocatalytic system enabled two sequential C-O bond formations to take place in an atom economical manner via highly efficient dual activation. Molecular oxygen in air could be utilized as a source of an oxygen atom for the oxidation of aldehydes to the corresponding benzoic acids under our newly developed reagent system.


Assuntos
Alquinos/química , Benzaldeídos/química , Compostos Heterocíclicos com 2 Anéis/síntese química , Catálise , Ciclização , Estrutura Molecular , Oxirredução
18.
Org Lett ; 12(10): 2258-61, 2010 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-20429502

RESUMO

Facile and efficient Rh(I)-catalyzed domino conjugate addition-cyclization reactions of olefins bearing two electrophilic sites and a pendant nucleophile with organoboroxines have been developed to afford a variety of N- and O-heterocycles, such as 3,4-dihydroquinolin-2(1H)-ones, 3,4-dihydrocoumarins, and pyrrolidin-2-ones, which constitute important motifs in biologically active natural and synthetic organic compounds.


Assuntos
Alcenos/química , Ácidos Borônicos/química , Compostos Heterocíclicos/síntese química , Compostos Organometálicos/química , Ródio/química , Catálise , Cumarínicos/síntese química , Cumarínicos/química , Ciclização , Compostos Heterocíclicos/química , Estrutura Molecular , Pirrolidinonas/síntese química , Pirrolidinonas/química , Quinolinas/síntese química , Quinolinas/química , Estereoisomerismo
19.
Org Lett ; 11(12): 2583-6, 2009 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-19514793

RESUMO

These studies provide an efficient and stereoselective synthetic route to (+)-MK7607 and its C-1 epimer from a common intermediate in high overall yields. The synthetic methodologies mainly rely on the stereospecific 1,3-allylic transposition of the hindered tertiary alcohol group through a palladium-catalyzed allylic rearrangement as well as a PBr(3)-mediated allylic-transposed bromination.


Assuntos
Galactose/química , Fenóis/síntese química , Propanóis/química , Catálise , Estrutura Molecular , Paládio/química , Fenóis/química , Estereoisomerismo
20.
J Org Chem ; 73(14): 5658-61, 2008 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-18557646

RESUMO

A new Rh(I)-catalyzed tandem conjugate addition-Mannich cyclization reaction of imine-substituted electron-deficient alkenes with arylboronic acids has been developed to afford 2,3,4-trisubstituted 1,2,3,4-tetrahydroquinolines. This is the first example involving imine group as a secondary electrophile in Rh(I)-catalyzed tandem reactions.

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