A Novel Classification of Lewis Acids on the Basis of Activity and Selectivity

Kobayashi, Shū; Busujima, Tsuyoshi; Nagayama, Satoshi

doi:10.1002/1521-3765(20001002)6:19<3491::aid-chem3491>3.3.co;2-g

Cited by 143 publications

(68 citation statements)

References 25 publications

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“…NbCl 5 forms chloro-bridged dimers in its solid state in which each niobium atom is surrounded by a distorted octahedron of chlorine atoms. NbCl 5 is highly electrophilic and can act as a Lewis acid, promoting several organic transformations (Batista et al, 1997;Kobayashi et al, 2000;Constantino et al, 2001Constantino et al, , 2004Constantino et al, , 2005Constantino et al, , 2007Andrade, 2004;da Silva-Filho et al, 2005Andrade & Rocha, 2006;Wang et al, 2007;Polo et al, 2008;Cai et al, 2010;Hou et al, 2010Hou et al, , 2011Lacerda et al, 2012;Liu et al, 2013;Martins et al, 2013;dos Santos et al, 2013;Bian et al, 2014;Nasseri et al, 2014).…”

Section: Introductionsupporting

confidence: 81%

Efficient one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives promoted by niobium pentachloride

2014

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Section: Introductionsupporting

confidence: 81%

Efficient one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives promoted by niobium pentachloride

2014

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“…It has been reported that the Strecker reaction of acetophenone even with the activated amine 3,4,5-trimethylaniline using metal triflates and acetonitrile as the solvent gave very poor yield of the product (47)(48)(49). We found that a similar reaction of acetophenone with aniline and TMSCN (cyanide source) in dichloromethane using Ga(OTf) 3 as a catalyst proceeds smoothly under mild conditions (room temperature, 5 h) giving the corresponding ␣-aminonitrile in excellent yield and high purity ( Table 2, entry 1), despite that the direct Strecker reaction using aromatic ketones and aromatic amines has been repeatedly cited in the literature as a challenge (6,7,(37)(38)(39)(40)(41)(42)(43)(44)(45)(46).…”

Section: Resultsmentioning

confidence: 77%

“…The Strecker reaction with aldehydes has been studied extensively with a variety of catalysts (37-46) including a number of metal triflates (47)(48)(49). However, the reactions are not feasible for ketones.…”

Section: Resultsmentioning

confidence: 99%

“…These results point toward the need of the proper catalyst and solvent system (suitable metal triflate as a catalyst and dichloromethane as a solvent in present cases), which play the key role for the success of the reaction. In earlier studies (37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49), acetonitrile and toluene were used as solvents; however, these are not suitable for the Lewis acid catalyzed direct Strecker reaction of ketones due to their interaction with the catalyst. The use of dichloromethane minimizes such interaction, resulting in enhanced catalytic activity of the catalyst toward ketones and providing a suitable environment for the reaction.…”

Section: Resultsmentioning

confidence: 99%

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Gallium (III) triflate catalyzed efficient Strecker reaction of ketones and their fluorinated analogs

Prakash

Mathew

Panja

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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The synthesis of ␣-aminonitriles and their fluorinated analogs has been carried out in high yield and purity by the Strecker reaction from the corresponding ketones and amines with trimethylsilyl cyanide using gallium triflate in dichloromethane. Monofluoro-, difluro-, or trifluoromethyl groups can be incorporated into the ␣-aminonitrile product by varying the nature of the fluorinated ketones. Study with various fluorinated and nonfluorinated ketones reveals that the choice of proper catalyst and the solvent system (suitable metal triflates as a catalyst and dichloromethane as a solvent) plays the key role in the direct Strecker reactions of ketones.three-component reaction ͉ ␣-aminonitriles

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“…The reaction mechanism is considered to involve a ternary complex, in which both the 1,3-dicarbonyl compound and the enone are coordinated to a Lewis-acid metal center. 58 A shift in the infrared (IR) spectrum of the coordinated ketone is a measure of the Lewis-acid strength of metal cations. 95 The IR spectrum of the (CO) band of adsorbed cyclopentanone onto Cu 2þ -mont appeared at 1685 cm À1 , which nþ -monts play an important role in these carbon-carbon bond-forming reactions.…”

mentioning

confidence: 99%

Design of High-Performance Heterogeneous Metal Catalysts for Green and Sustainable Chemistry

Kaneda¹,

Ebitani²,

Mizugaki³

et al. 2006

Bulletin of the Chemical Society of Japan

143

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This account reviews a novel approach to designing high-performance heterogeneous metal catalysts using hydroxyapatites, montmorillonites, and hydrotalcites as macroligands of active metal species for aerobic alcohol oxidations, carbon-carbon bond formations, and one-pot syntheses. The catalytic systems using the above heterogeneous catalysts offer significant benefits in achieving environmentally friendly organic syntheses aiming towards Green and Sustainable Chemistry. Furthermore, the present preparation method for the immobilization of metal species is strikingly simple and allows a strong protocol for creating various nanostructured and functionalized heterogeneous catalysts.Green and Sustainable Chemistry (GSC) is a revolutionary philosophy that aims to bring about a sustainable society by improvement of the safety and environmental aspects of chemical processes and reduction of the risks of chemical products to people and the environment.1 The emphasis is on eliminating waste at the source-primary pollution prevention-rather than finding incremental end-of-pipe solutions. This concept aims to solve the societal problems of the last century associated with the mass production and consumption of materials, and plays a prime role in providing a venous function in society, encouraging reuse and circulation of resources.One of the powerful solutions in the move toward GSC is the replacement of traditional synthetic methods using harmful stoichiometric reagents that produce vast amounts of waste with cleaner and simple catalytic alternatives with high atom efficiency 1a and low E-factors. 1b Catalytic chemistry, therefore, is of ever-increasing importance because catalysis is a key element in material transformations at atomic and molecular levels, which are an essential realm of chemistry and chemical processes.Our approach to GSC is to develop a highly functionalized heterogeneous metal catalyst based on the unique characteristics of natural layered inorganic materials such as hydroxyapatite, montmorillonite, and hydrotalcite, by using them as macroligands for metal species.2 We consider the above inorganic materials to be advanced nano-scaled catalyst supports allowing for the control of the location of catalytically active metal species, which can be found, for example, on the surface, among the layers, or in the interlayer space. Furthermore, these materials are capable of creating catalytically active metal species responsible for targeted organic transformations involving monomers, chain-like species or giant clusters. The creation of well-defined active metal sites on a solid surface, as characterized by X-ray absorption spectroscopy, not only opens up an avenue to materials that boost catalytic performance, but also aids in the understanding of the molecular basis of heterogeneous catalysis. Another advantage of these catalysts is the possibility of a one-pot synthesis based on a cooperative action by several immobilized active species on the solid surface as multifunctional catalysts. The target react...

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A Novel Classification of Lewis Acids on the Basis of Activity and Selectivity

Cited by 143 publications

References 25 publications

Efficient one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives promoted by niobium pentachloride

Efficient one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives promoted by niobium pentachloride

Gallium (III) triflate catalyzed efficient Strecker reaction of ketones and their fluorinated analogs

Design of High-Performance Heterogeneous Metal Catalysts for Green and Sustainable Chemistry

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