- Synthesis of rac-ɑ-aryl propionaldehydes via branched-selective hydroformylation of terminal arylalkenes using water-soluble Rh-PNP catalyst
-
This work detailed the preparation of a class of water-soluble PNP ligands that differed by the nature of the substitute on phenyl ring of ligands. These ligands were incorporated into water-soluble rhodium-PNP complex catalysts that were used to regioselective hydroformylation of a series of terminal arylalkenes, providing efficient access to rac-α-aryl propionaldehydes in good to excellent yield (up to 97%) and branched-regioselectivity (up to 40:1 b/l ratio). Furthermore, gram-scale and diverse synthetic transformation demonstrated synthetic application of this methodology for non-steroidal antiinflammatory drugs.
- Chen, Fen-Er,Gao, Peng,Ke, Miaolin,Liang, Guanfeng,Ru, Tong
-
-
- Insight into decomposition of formic acid to syngas required for Rh-catalyzed hydroformylation of olefins
-
Formic acid (FA) is one kind of important bulk chemicals, which is recognized as a sustainable and eco-friendly energy carrier to transport H2 via dehydrogenation or CO via decarbonylation. Expectantly, FA upon decomposition into H2 and CO could be used as the syngas alternative for hydroformylation. In this paper, the behaviors of FA to release H2 as well as CO following the distinct pathways were carefully investigated for the first time, and then established a new hydroformylation protocol free of syngas. It was found that the atmospheric hydroformylation of olefins with formic acid (FA) as syngas alternative was smoothly fulfilled over Xantphos (L1) modified Rh-catalyst under mild conditions (80 °C, Rh concentration 1 mol %, 14 h), resulting in >90% conversion of the olefins along with the high selectivity to the target aldehydes (>93%). By using FA as syngas source, the side-reaction of olefin-hydrogenation was greatly depressed. The in situ FT-IR and the high-pressure 1H NMR spectroscopic analyses were applied to reveal how FA behaves dually as CO surrogate and hydrogen source over L1-Rh(acac)(CO)2 catalytic system, based on which the deeply insight into the catalytic mechanism of hydroformylation of olefins with FA as syngas alternative was offered.
- Liu, Lei,Chen, Xiao-Chao,Yang, Shu-Qing,Yao, Yin-Qing,Lu, Yong,Liu, Ye
-
p. 406 - 415
(2020/12/07)
-
- An Asymmetric SN2 Dynamic Kinetic Resolution
-
The SN2 reaction exhibits the classic Walden inversion, indicative of the stereospecific backside attack of the nucleophile on the stereogenic center. Observation of the inversion of the stereocenter provides evidence for an SN2-type displacement. However, this maxim is contingent on substitution proceeding on a discrete stereocenter. Here we report an SN2 reaction that leads to enantioenrichment of product despite starting from a racemic mixture of starting material. The enantioconvergent reaction proceeds through a dynamic Walden cycle, involving an equilibrating mixture of enantiomers, initiated by a chiral aminocatalyst and terminated by a stereoselective SN2 reaction at a tertiary carbon to provide a quaternary carbon stereocenter. A combination of computational, kinetic, and empirical studies elucidates the multifaceted role of the chiral organocatalyst to provide a model example of the Curtin-Hammett principle. These examples challenge the notion of enantioenriched products exclusively arising from predefined stereocenters when operating through an SN2 mechanism. Based on these principles, examples are included to highlight the generality of the mechanism. We anticipate the asymmetric SN2 dynamic kinetic resolution to be used for a variety of future reactions.
- Rezayee, Nomaan M.,Enem?rke, Valdemar J.,Linde, Sif T.,Lamhauge, Johannes N.,Reyes-Rodríguez, Gabriel J.,J?rgensen, Karl Anker,Lu, Chenxi,Houk
-
supporting information
p. 7509 - 7520
(2021/05/26)
-
- Copper-catalyzed hydroformylation and hydroxymethylation of styrenes
-
Hydroformylation catalyzed by transition metals is one of the most important homogeneously catalyzed reactions in industrial organic chemistry. Millions of tons of aldehydes and related chemicals are produced by this transformation annually. However, most of the applied procedures use rhodium catalysts. In the procedure described here, a copper-catalyzed hydroformylation of alkenes has been realized. Remarkably, by using a different copper precursor, the aldehydes obtained can be further hydrogenated to give the corresponding alcohols under the same conditions, formally named as hydroxymethylation of alkenes. Under pressure of syngas, various aldehydes and alcohols can be produced from alkenes with copper as the only catalyst, in excellent regioselectivity. Additionally, an all-carbon quaternary center containing ethers and formates can be synthesized as well with the addition of unactivated alkyl halides. A possible reaction pathway is proposed based on our results. This journal is
- Franke, Robert,Geng, Hui-Qing,Meyer, Tim,Wu, Xiao-Feng
-
p. 14937 - 14943
(2021/12/02)
-
- Highly Enantioselective Synthesis of Propargyl Amide with Vicinal Stereocenters through Ir-Catalyzed Hydroalkynylation
-
Chiral propargyl amines are valuable synthetic intermediates for the preparation of biologically active compounds and functionalized amines. Catalytic methods to access propargyl amines containing vicinal stereocenters with high diastereoselectivity are particularly rare. We report an unprecedented strategy for the synthesis of enantioenriched propargyl amines with two stereogenic centres. An iridium complex, ligated by a phosphoramidite ligand, catalyzes the hydroalkynylation of β,β-disubstituted enamides to afford propargyl amides in a highly regio-, diastereo-, and enantioselective fashion. Stereodivergent synthesis of all four possible stereoisomers was achieved using this strategy.
- Li, Bi-Jie,Zhang, Su-Lei,Zhang, Wen-Wen
-
supporting information
p. 6874 - 6880
(2020/03/19)
-
- Binuclear Pd(I)-Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes
-
Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>107 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh- or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)-Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.
- Zhang, Yang,Torker, Sebastian,Sigrist, Michel,Bregovi?, Nikola,Dydio, Pawe?
-
supporting information
p. 18251 - 18265
(2020/11/02)
-
- Mild Iridium-Catalysed Isomerization of Epoxides. Computational Insights and Application to the Synthesis of β-Alkyl Amines
-
The isomerization of epoxides to aldehydes using the readily available Crabtree's reagent is described. The aldehydes were transformed into synthetically useful amines by a one-pot reductive amination using pyrrolidine as imine-formation catalyst. The reactions worked with low catalyst loadings in very mild conditions. The procedure is operationally simple and tolerates a wide range of functional groups. A DFT study of its mechanism is presented showing that the isomerization takes place via an iridium hydride mechanism with a low energy barrier, in agreement with the mild reaction conditions. (Figure presented.).
- Cabré, Albert,Cabezas-Giménez, Juanjo,Sciortino, Giuseppe,Ujaque, Gregori,Verdaguer, Xavier,Lledós, Agustí,Riera, Antoni
-
p. 3624 - 3631
(2019/07/10)
-
- MICROCAPSULES AND PROCESSES FOR THEIR PREPARATION
-
The present invention provides microcapsules encapsulating hydrophilic or hydrophobic active agents in an inorganic shell, processes for their preparation and compositions comprising them.
- -
-
Page/Page column 28-30
(2019/06/11)
-
- Copper-catalyzed vinylogous aerobic oxidation of unsaturated compounds with air
-
A mild and operationally simple copper-catalyzed vinylogous aerobic oxidation of β,γ- and α,β-unsaturated esters is described. This method features good yields, broad substrate scope, excellent chemo- and regioselectivity, and good functional group tolerance. This method is additionally capable of oxidizing β,γ- and α,β-unsaturated aldehydes, ketones, amides, nitriles, and sulfones. Furthermore, the present catalytic system is suitable for bisvinylogous and trisvinylogous oxidation. Tetramethylguanidine (TMG) was found to be crucial in its role as a base, but we also speculate that it serves as a ligand to copper(II) triflate to produce the active copper(II) catalyst. Mechanistic experiments conducted suggest a plausible reaction pathway via an allylcopper(II) species. Finally, the breadth of scope and power of this methodology are demonstrated through its application to complex natural product substrates.
- Zhang, Hai-Jun,Schuppe, Alexander W.,Pan, Shi-Tao,Chen, Jin-Xiang,Wang, Bo-Ran,Newhouse, Timothy R.,Yin, Liang
-
supporting information
p. 5300 - 5310
(2018/04/24)
-
- Asymmetric α-Allylation of Aldehydes with Alkynes by Integrating Chiral Hydridopalladium and Enamine Catalysis
-
A palladium-catalyzed asymmetric α-allylation of aldehydes with alkynes has been established by integrating the catalysis of enamine and chiral hydridopalladium complex that is reversibly formed from the oxidative addition of Pd(0) to chiral phosphoric acid. The ternary catalyst system, consisting of an achiral palladium complex, a primary amine, and a chiral phosphoric acid allows the reaction to tolerate a wide scope of α,α-disubstituted aldehydes and alkynes, affording the corresponding allylation products in high yields and with excellent levels of enantioselectivity.
- Su, Yong-Liang,Li, Lu-Lu,Zhou, Xiao-Le,Dai, Zhen-Yao,Wang, Pu-Sheng,Gong, Liu-Zhu
-
supporting information
p. 2403 - 2406
(2018/04/27)
-
- Rhodium-catalyzed asymmetric hydrogenation of β-branched enamides for the synthesis of β-stereogenic amines
-
Using a rhodium complex of a bisphosphine ligand (R)-SDP, β-branched simple enamides with a (Z)-configuration were hydrogenated to β-stereogenic amines in quantitative yields and with excellent enantioselectivities (88-96% ee).
- Zhang, Jian,Liu, Chong,Wang, Xingguang,Chen, Jianzhong,Zhang, Zhenfeng,Zhang, Wanbin
-
supporting information
p. 6024 - 6027
(2018/06/18)
-
- Biocatalytic Parallel Interconnected Dynamic Asymmetric Disproportionation of α-Substituted Aldehydes: Atom-Efficient Access to Enantiopure (S)-Profens and Profenols
-
The biocatalytic asymmetric disproportionation of aldehydes catalyzed by horse liver alcohol dehydrogenase (HLADH) was assessed in detail on a series of racemic 2-arylpropanals. Statistical optimization by means of design of experiments (DoE) allowed the identification of critical interdependencies between several reaction parameters and revealed a specific experimental window for reaching an ′optimal compromise′ in the reaction outcome. The biocatalytic system could be applied to a variety of 2-arylpropanals and granted access in a redox-neutral manner to enantioenriched (S)-profens and profenols following a parallel interconnected dynamic asymmetric transformation (PIDAT). The reaction can be performed in aqueous buffer at ambient conditions, does not rely on a sacrificial co-substrate, and requires only catalytic amounts of cofactor and a single enzyme. The high atom-efficiency was exemplified by the conversion of 75 mM of rac-2-phenylpropanal with 0.03 mol% of HLADH in the presence of ~0.013 eq. of oxidized nicotinamide adenine dinucleotide (NAD+), yielding 28.1 mM of (S)-2-phenylpropanol in 96% ee and 26.5 mM of (S)-2-phenylpropionic acid in 89% ee, in 73% overall conversion. Isolated yield of 62% was obtained on 100 mg-scale, with intact enantiopurities. (Figure presented.).
- Tassano, Erika,Faber, Kurt,Hall, Mélanie
-
supporting information
p. 2742 - 2751
(2018/07/29)
-
- Calix[4]arene-fused phospholes
-
An upper rim, o-(diphenylphosphinyl)phenyl-substituted calix[4]arene has been prepared and its coordinative properties investigated. When heated in the presence of palladium, the new biarylphosphine undergoes conversion into two diastereomeric, calixarene-fused phospholes. In both, the P lone pair adopts a fixed orientation with respect to the calixarene core. The more hindered phosphole (8), i.e. the one with the endo-oriented lone pair (cone angle 150°-175°), forms complexes having their metal centre positioned very near the calixarene unit but outside the cavity, thus inducing an unusual chemical shift of one of the methylenic ArCH2Ar protons owing to interactions with the metal centre. As expected for dibenzophospholes, the complex [Rh(acac)(CO)·8], when combined with one equivalent of free 8, efficiently catalyses the hydroformylation of styrene, the catalytic system displaying high regioselectivity in favour of the branched aldehyde (b/l ratio up to 30). The optical and redox properties of the derivatives have also been investigated.
- Elaieb, Fethi,Sémeril, David,Matt, Dominique,Pfeffer, Michel,Bouit, Pierre-Antoine,Hissler, Muriel,Gourlaouen, Christophe,Harrowfield, Jack
-
p. 9833 - 9845
(2017/08/10)
-
- Direct Synthesis of α-Allenols from TMS-Protected Alkynes and Aldehydes Mediated by Tetrabutylammonium Fluoride
-
A unique chemoselective synthesis of α-allenic alcohols is presented. Tetrabutylammonium fluoride (TBAF) mediated this transformation under mild reaction conditions. A range of functional groups is well-tolerated in this reaction, while affording adducts
- Huang, Xiaojun,Bugarin, Alejandro
-
supporting information
p. 12696 - 12700
(2016/08/30)
-
- Rhodium-complexed hyperbranched poly(ethyleneimine) and polyamidoamine and their non-covalent immobilization on magnetic nanoparticles
-
We describe a synthetic strategy for the synthesis and functionalization of hyperbranched poly(ethyleneimine) (H-PEI) and polyamidoamine (H-PAMAM) with phosphine ligands and their non-covalent immobilization on magnetic nanosupports. Treatment of these functionalized hyperbranched polymers with Rh(COD)2BF4 affords polymer-bound Rh(I) complexes that can be utilized in the hydroformylation of alkenes and in one pot hydroformylation-Knoevenagel-hydrogenation reactions. These functionalized hyperbranched polymers are linked to magnetic nanoparticles that are modified with carboxylic acid groups via ionic interactions resulting from the acid-base reactions, and are responsible for facilitating the separation of the polymeric catalysts. These magnetically retrievable polymeric catalysts can be reused for up to four cycles.
- Omar, Suheir,Dutta, Bishnu,Natour, Suzana,Abu-Reziq, Raed
-
-
- Promotion effect of water on hydroformylation of styrene and its derivatives with presence of amphiphilic zwitterionic phosphines
-
Two kinds of novel zwitterionic phosphines of L1 and L2 have been synthesized in which the sulfonate groups (-SO3-) are incorporated to render them amphiphilic. Both of them are strong π-acceptor ligands in which the positive-charged imidazoliums with intensive electron-withdrawing effect are vicinal to the coordinating phosphorous atoms. The amino-group of piperidyl is additionally incorporated in L2 to make it behave as a hybrid ligand with potential hemilability. The comparison of the ligands of L1 and L2 in Rh-catalyzed hydroformylation of styrene (and its derivatives) and the effect of water on their behaviors were discussed. Without the involvement of water, the catalytic system of Rh(acac)(CO)2-L2 exhibited lower activity than that of Rh(acac)(CO)2-L1 under the same conditions. However, the dramatic promotion effect of water as a suspension was observed especially for Rh(acac)(CO)2-L2 system with TOF spurred up from 195 to 470 h-1. The corresponding in situ high pressure FT-IR spectral information showed that the presence of water in Rh(acac)(CO)2-L2 system greatly facilitated the formation and stability of the active Rh-H species (νRh-H, 2047 cm-1), which was in charge of the efficient hydroformylation of styrene and its derivatives.
- Chen, Sheng-Jie,Li, Yong-Qi,Wang, Peng,Lu, Yong,Zhao, Xiao-Li,Liu, Ye
-
p. 212 - 220
(2015/07/28)
-
- Dual Catalytic Activity of Palladium Doped with a Rhodium Complex in a One-pot, Four Step Process
-
The extraction of the two competing reactions from the same catalyst - a composite catalytic-complex@catalytic-metal - is reported. A Wilkinson rhodium based catalyst entrapped within metallic palladium catalyst is shown to perform both hydroformylation and hydrogenation with a ratio that depends on H2 and CO pressures. Here we demonstrate this special reactivity in a one-pot, four step sequence, which include hydroformylations of phenyl acetylenes, reduction of nitrobenzene to aniline, carbonyl-amine condensations forming imines; and imine reductions.
- Shapiro, Leora,Driess, Matthias,Avnir, David
-
p. 2033 - 2037
(2015/11/24)
-
- The catalytic asymmetric α-benzylation of aldehydes
-
The first aminocatalyzed α-alkylation of α-branched aldehydes with benzyl bromides as alkylating agents has been developed. Using a sterically demanding proline derived catalyst, racemic α-branched aldehydes are reacted with alkylating agents in a DYKAT process to give the corresponding α-alkylated aldehydes with quaternary stereogenic centers in good yields and high enantioselectivities. A sterically demanding proline derivative promotes the first aminocatalyzed α-alkylation of α-branched aldehydes with benzyl bromides as alkylating agents. Racemic α-branched aldehydes react with alkylating agents in a DYKAT process to give the corresponding α-alkylated aldehydes with quaternary stereogenic centers in good yields and high enantioselectivities. Copyright
- List, Benjamin,Coric, Ilija,Grygorenko, Oleksandr O.,Kaib, Philip S. J.,Komarov, Igor,Lee, Anna,Leutzsch, Markus,Chandra Pan, Subhas,Tymtsunik, Andrey V.,Van Gemmeren, Manuel
-
supporting information
p. 282 - 285
(2014/01/17)
-
- An air-stable cationic iridium hydride as a highly active and general catalyst for the isomerization of terminal epoxides
-
We describe the use of an air-stable iridium hydride catalyst for the isomerization of terminal epoxides into aldehydes with perfect regioselectivity. The system operates at low loadings of catalyst (0.5 mol%), is highly practical, scalable, and tolerates functional groups that would not be compatible with Lewis acids typically used in stoichiometric amounts. Evidence for a rare hydride mechanism are provided. This journal is the Partner Organisations 2014.
- Humbert, Nicolas,Vyas, Devendra J.,Besnard, Céline,Mazet, Clément
-
supporting information
p. 10592 - 10595
(2014/10/15)
-
- Synthesis of chiral butenolides using amino-thiocarbamate-catalyzed asymmetric bromolactonization
-
The asymmetric cyclization of 4,4-disubstituted 3-butenoic acids is studied. Amino-thiocarbamates are used as the catalysts and N-bromosuccinimide is used as the stoichiometric halogen source. The resulting γ-butanolide products are readily converted into the corresponding γ-butenolides (up to 58% ee) derivatives in one-pot.
- Tan, Chong Kiat,Er, Jun Cheng,Yeung, Ying-Yeung
-
p. 1243 - 1246
(2014/02/14)
-
- Flow Chemistry Syntheses of Styrenes, Unsymmetrical Stilbenes and Branched Aldehydes
-
Two tandem flow chemistry processes have been developed. A single palladium-catalysed Heck reaction with ethylene gas provides an efficient synthesis for functionalised styrenes. Through further elaboration the catalyst becomes multi-functional and performs a second Heck reaction providing a single continuous process for the synthesis of unsymmetrical stilbenes. In addition, the continuous, rhodium-catalysed, hydroformylation of styrene derivatives with syngas affords branched aldehydes with good selectivity. Incorporation of an in-line aqueous wash and liquid-liquid separation allowed for the ethylene Heck reaction to be telescoped into the hydroformylation step such that a single flow synthesis of branched aldehydes directly from aryl iodides was achieved. The tube-in-tube semi-permeable membrane-based gas reactor and liquid-liquid separator both play an essential role in enabling these telescoped flow processes.
- Bourne, Samuel L.,O'Brien, Matthew,Kasinathan, Sivarajan,Koos, Peter,Tolstoy, Paeivi,Hu, Dennis X.,Bates, Roderick W.,Martin, Benjamin,Schenkel, Berthold,Ley, Steven V.
-
p. 159 - 172
(2013/03/13)
-
- Isomerization of terminal epoxides by a [Pd-H] catalyst: A combined experimental and theoretical mechanistic study
-
An unusual palladium hydride complex has been shown to be a competent catalyst in the isomerization of a variety of terminal and internal epoxides. The reaction displayed broad scope and synthetic utility. Experimental and theoretical evidence are provided for an unprecedented hydride mechanism characterized by two distinct enantio-determining steps. These results hold promise for the development of an enantioselective variant of the reaction.
- Vyas, Devendra J.,Larionov, Evgeny,Besnard, Celine,Guenee, Laure,Mazet, Clement
-
p. 6177 - 6183
(2013/06/04)
-
- Complementary catalytic strategies to access α-chiral aldehydes
-
The present article summarizes the development of two novel and complementary catalytic methods to access α-chiral aldehydes. A C1-symmetric chiral (P,N) ligand with a structure derived from the ubiquitous binepine scaffold has been specifically designed for the Pd-catalyzed α arylation of aldehydes to access indane derivatives with a well-defined quaternary stereocenter in high yields and excellent enantioselectivities. In addition, a dinuclear palladium hydride catalyst has been synthesized for the isomerization of terminal and trisubstituted epoxides into aldehydes and ketones respectively. Combined experimental and theoretical investigations pointed to an unprecedented 'epoxide-opening/hydride-transfer' sequence. The mechanism also features two distinct enantio-determining steps in the kinetic resolution of racemic epoxides. Schweizerische Chemische Gesellschaft.
- Mazet, Clement
-
p. 658 - 662
(2013/11/06)
-
- β-tert-Butyl aspartate as an organocatalyst for the asymmetric α-amination of α,α-disubstituted aldehydes
-
The enantioselective α-amination reaction of α,α- disubstituted aldehydes can lead to a variety of enantioenriched amino aldehydes, amino alcohols, and amino acids. After screening a variety of amino acids and their derivatives, we identified a cheap, simple, commercially available aspartic acid derivative that can catalyze efficiently the reaction between α,α-disubstituted aldehydes and dialkyl azodicarboxylates. The reaction proceeds smoothly leading to the corresponding α-aminated adducts in moderate to quantitative yields and moderate to high enantioselectivities (up to 96% ee). Finally, the conversion of these adducts to α,α-disubstituted quaternary amino acids is also described.
- Theodorou, Alexis,Papadopoulos, Giorgos N.,Kokotos, Christoforos G.
-
supporting information
p. 5438 - 5443
(2013/07/05)
-
- Regioselective hydroformylation of vinylarenes in aqueous media by a sol-gel entrapped rhodium catalyst
-
Two methods for selective hydroformylation of vinylarenes in aqueous media are described. One method relies on the application of [Rh(cod)Cl]2 and a tertiary phosphane entrapped within an ionic liquid-confined silica sol-gel support. The second method utilizes the same rhodium compound, encaged within ionic-liquid-free hydrophobicized sol-gel. Both methods are best carried out at 50 °C in aqueous emulsions or microemulsions that consist of the substrate, a surfactant, a co-surfactant and >89% water. The optimal H 2/CO ratio is between 1 and 1.1. Both methods allow the reuse of the heterogenized catalyst for several runs. While the regioselectivity and the yield are hardly affected by the electronic nature of the substrates, they are significantly dependent on the reaction temperature, on the surfactant employed, and on the hydrophobicity of the support of the catalyst. Despite the use of H2 in the reactions, no transformation of the organometallic catalyst into metallic nanoparticles could be detected.
- Nairoukh, Zackaria,Blum, Jochanan
-
scheme or table
p. 129 - 133
(2012/06/18)
-
- Syngas-mediated C-C bond formation in flow: Selective rhodium-catalysed hydroformylation of styrenes
-
We report a continuous flow, rhodium-catalysed hydroformylation of various styrenes using a tube-in-tube gas-liquid reactor. The flow process afforded selectively branched aryl aldehydes in good yields. Georg Thieme Verlag Stuttgart · New York.
- Kasinathan, Sivarajan,Bourne, Samuel L.,Tolstoy, P?ivi,Koos, Peter,Obrien, Matthew,Bates, Roderick W.,Baxendale, Ian R.,Ley, Steven V.
-
scheme or table
p. 2648 - 2651
(2011/12/04)
-
- Synthesis, complexation behavior and application of a new diphosphite ligand in rhodium-catalyzed hydroformylation
-
Oxidative coupling of 3-(3-tert-butyl-4-hydroxyphenyl)propionic acid methyl ester (2) gave dimethyl 3,3′-(5,5′-di-tert-butyl-6,6′- dihydroxybiphenyl-3,3′-diyl)-dipropionate (1c), which upon phosphorylation/transesterification with a phosphochloridite derived from (R)-binaphthol, formed the new unsymmetrical binaphthol-bridged diphosphite 4. A rhodium catalyst based on 4 as ligand gave predominantly iso-selectivity in the hydroformylation of selected styrenes but opposite regioselectivity with 2,6-disubstituted derivatives. New chelate metal complexes (acac)RhL, PdCl 2L and PtCl2L have been synthesized by reacting 4 with (acac)Rh(CO)2, PdCl2(MeCN)2 and PtCl 2(COD), respectively. The structure of obtained compounds is determined based on 1H, 13C, 31P and 195Pt NMR spectroscopy and mass spectrometry data.
- Mikhel, Igor S.,Dubrovina, Natalia V.,Shuklov, Ivan A.,Baumann, Wolfgang,Selent, Detlef,Jiao, Haijun,Christiansen, Andrea,Franke, Robert,Boerner, Armin
-
experimental part
p. 3050 - 3057
(2011/09/20)
-
- Effective construction of quaternary stereocenters by highly enantioselective α-amination of branched aldehydes
-
A highly efficient enantioselective α-amination of branched aldehydes with azadicarboxylates promoted by chiral proline-derived amide thiourea bifunctional catalysts was developed for the first time, affording the adducts bearing quaternary stereogenic centers with excellent yields (up to 99%) and enantioselectivities (up to 97% ee).
- Fu, Ji-Ya,Xu, Xiao-Ying,Li, Yan-Chun,Huang, Qing-Chun,Wang, Li-Xin
-
supporting information; experimental part
p. 4524 - 4526
(2010/11/21)
-
- The proline-catalyzed asymmetric amination of branched aldehydes
-
An efficient access to configurationally stable α,β- disubstituted α-amino aldehydes, oxazolidinones, and α-amino acids has been presented. Starting from simple and easily available racemic aldehydes, the α-aminated products were obtained using azodicarboxylates as the nitrogen source in up to 86 % ee and moderate to excellent yield. These products could further be converted both into the corresponding α-amino alcohols and, depending on the residue of the azodicarboxylates and the reaction conditions, into the oxazolidinones. On the other hand, oxidation towards the carboxylic acid and cleavage of the hydrazide bond under mild conditions revealed the free α-alkylated phenylglycine derivative. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Baumann, Thomas,Vogt, Henning,Braese, Stefan
-
p. 266 - 282
(2007/10/03)
-
- Highly selective hydroformylation of vinylarenes to branched aldehydes by [Rh(cod)Cl]2 entrapped in ionic liquid modified silica sol-gel
-
A co-entrapped mixture of [Rh(cod)Cl]2 and Na[Ph 2P-3-(C6H4SO3)] within a silica sol-gel matrix modified with ca. 5% of 1-butyl-3-[3-(trimethoxysilyl)propyl] imidazolium chloride catalyzes, in n-heptane, the hydroformylation of a variety of vinylarenes. At 50°C and under 6.9 bar each of H2 and CO the reaction is high-yielding and highly selective. Non-hindered substrates give >95 % of branched aldehydes and only 5% of the linear isomers. The ceramic catalyst is leach-proof and recyclable. It does not lose its high catalytic activity and selectivity for at least four runs. The selectivity depends on the pressure of the gases, the temperature and the solvent. The electronic nature has no influence on the selectivity, but the latter is diminished by steric effects. Upon omission of the sol-gel component, the catalyst deteriorates and practically loses its activity after the first half-life of the reaction. In the absence of the ionic liquid, the catalyst undergoes substantial leaching. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Hamza, Khalil,Blum, Jochanan
-
p. 4706 - 4710
(2008/03/13)
-
- New aromatic rearrangement accompanying ring closure of 2-arylpropylidenemalonodinitriles to 1-aminonaphthalene-2-carbonitriles
-
Cyclization and a rearrangement in concentrated sulfuric acid of 2-(4-substituted-phenyl)propylidenemalonodinitriles (1) into 1-amino-4-methyl-6-substituted-naphthalene-2-carbonitriles (5) appears to involve a series of steps such as ipso electrophilic attack of the protonated nitrile function on the para position of the phenyl group, opening of a spirobenzenium cation or its transformation, and ring reclosure to the naphthalene framework with participation of the secondary alkyl carbocation as an active electrophile.
- Sepiol, Janusz J,Wilamowski, Jaroslaw
-
p. 5287 - 5289
(2007/10/03)
-
- Aminocyclohexane derivatives as 5-HT receptor agonists
-
A class of substituted aminocyclohexane derivatives are selective agonists of 5-HT1-like receptors, being potent agonists of the human 5-HT1Dαreceptor subtype while possessing at least a 10-fold selective affinity for the
- -
-
-
- A new, efficient, and in some cases highly regioselective water-soluble polymer rhodium catalyst for olefin hydroformylation
-
A water-soluble complex Rh/PPA(Na+)/DPPEA 1 was obtained from poly(4- pentenoic acid) (PPA) and bis[2-(diphenylphosphino)ethyllamine (DPPEA). Complex 1 is a highly active catalyst for the hydroformylation of olefins. Some selectively for linear aldehydes was observed in the hydroformylation of aliphatic olefins, while high ratios of branched aldehydes resulted in the case of vinyl ethers. Complex 1 is also the first polymeric water-soluble metal complex which can catalyze the conversion of vinylarenes to 2- arylpropanals in a highly chemoselective and regioselective manner.
- Ajjou, Abdelaziz Nait,Alper, Howard
-
p. 1466 - 1468
(2007/10/03)
-