69831-13-6Relevant articles and documents
Enantioselective catalysts based on the chiral fragment (η5-C5Me5)Ir(Prophos) for Diels-Alder reactions
Carmona, Daniel,Viguri, Fernando,Asenjo, Ainara,Lahoz, Fernando J.,García-Ordu?a, Pilar,Oro, Luis A.
, p. 119 - 124 (2014)
The aqua complex (SIr,RC)-[(η5-C 5Me5)Ir(Prophos)(H2O)][SbF6] 2 [Prophos = (R)-propane-1,2-diyl-bis(diphenylphosphane)] is an active precursor for the asymmetric Diels-Alder reaction of acyclic enals with cyclopentadiene, 2,3-dimethylbutadiene and isoprene. Enantioselectivities up to 78% ee are achieved. The intermediate Lewis acid-dienophile complex (S Ir,RC)-[(η5-C5Me 5)Ir(Prophos)(ethyl acrolein)][SbF6]2 has been isolated and completely characterized, including the X-ray crystal structure determination. Structural parameters indicate that the disposition of the coordinated dienophile is controlled by CH/π attractive interactions established between a phenyl group of the Prophos ligand and the aldehyde proton of the coordinated enal. Proton NMR data indicate that these interactions are maintained in solution. From diffractometric and spectroscopic data, the origin of the enantioselectivity is discussed.
Bis-selenonium Cations as Bidentate Chalcogen Bond Donors in Catalysis
He, Xinxin,Wang, Xinyan,Tse, Ying-Lung Steve,Ke, Zhihai,Yeung, Ying-Yeung
, p. 12632 - 12642 (2021/10/21)
Lewis acids are frequently employed in catalysis but they often suffer from high moisture sensitivity. In many reactions, catalysts are deactivated because of the problem that strong Lewis acids also bond to the products. In this research, hydrolytically stable bidentate Lewis acid catalysts derived from selenonium dicationic centers have been developed. The bis-selenonium catalysts are employed in the activation of imine and carbonyl groups in various transformations with good yields and selectivity. Lewis acidity of the bis-selenonium salts was found to be stronger than that of the monoselenonium systems, attributed to the synergistic effect of the two cationic selenonium centers. In addition, the bis-selenonium catalysts are not inhibited by strong bases or moisture.
Method for preparing single-configuration C-2-position-monosubstituted norbornene derivative
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, (2021/07/01)
The invention discloses a method for preparing a single-configuration C-2-position-monosubstituted norbornene derivative. The method comprises the following steps of: firstly, preparing exo-isomer enriched exo-isomer mixed 5-norbornene-2-carboxylic ester by taking commercial exo-isomer/endoisomer mixed 5-norbornene-2-carboxylic acid and large-steric-hindrance monohydric alcohol as raw materials; separating 5-norbornene-2-carboxylate with a single configuration through common column chromatography separation or fractionation; and finally, preparing the C-2-position-monosubstituted norbornene derivative with the single configuration from the separated 5-norbornene-2-carboxylate with the single configuration. The raw materials used in the invention are easy to obtain, the preparation process is simple, and the C-2-position-monosubstituted norbornene derivative with high purity (greater than 98%) and single configuration can be obtained.
Improving the efficiency of the Diels-Alder process by using flow chemistry and zeolite catalysis
Seghers,Protasova,Mullens,Thybaut,Stevens
supporting information, p. 237 - 248 (2017/08/14)
The industrial application of the Diels-Alder reaction for the atom-efficient synthesis of (hetero)cyclic compounds constitutes an important challenge. Safety and purity concerns, related to the instability of the polymerization prone diene and/or dienophile, limit the scalability of the production capacity of Diels-Alder products in a batch mode. To tackle these problems, the use of a high-pressure continuous microreactor process was considered. In order to increase the yields and the selectivity towards the endo-isomer, commercially available zeolites were used as a heterogeneous catalyst in a microscale packed bed reactor. As a result, a high conversion (≥95%) and endo-selectivity (89:11) were reached for the reaction of cyclopentadiene and methyl acrylate, using a 1:1 stoichiometry. A throughput of 0.87 g h-1 during at least 7 h was reached, corresponding to a 3.5 times higher catalytic productivity and a 14 times higher production of Diels-Alder adducts in comparison to the heterogeneous lab-scale batch process. Catalyst deactivation was hardly observed within this time frame. Moreover, complete regeneration of the zeolite was demonstrated using a straightforward calcination procedure.
Remote Tris(pentafluorophenyl)borane-Assisted Chiral Phosphoric Acid Catalysts for the Enantioselective Diels-Alder Reaction
Hatano, Manabu,Ishihara, Hideyuki,Goto, Yuta,Ishihara, Kazuaki
, p. 564 - 570 (2016/03/12)
Tris(pentafluorophenyl)borane-assisted chiral supramolecular phosphoric acid catalysts were developed for the model Diels-Alder reaction of α-substituted acroleins with cyclopentadiene. Two remotely coordinated tris(pentafluorophenyl)boranes should help to increase the Bronsted acidity of the active center in the supramolecular catalyst and create effective bulkiness for the chiral cavity. The prepared supramolecular catalysts acted as not only conjugated Bronsted acid-Bronsted base catalysts but also bifunctional Lewis acid-Bronsted base catalysts with the addition of a central achiral Lewis acid source such as catecholborane.
Chiral Dawson-Type Hybrid Polyoxometalate Catalyzes Enantioselective Diels-Alder Reactions
Xuan, Wen-Jing,Botuha, Candice,Hasenknopf, Bernold,Thorimbert, Serge
supporting information, p. 16512 - 16516 (2015/11/09)
Can achiral organocatalysts linked to chiral polyanionic metal oxide clusters provide good selectivity in enantioselective C-C bond formations? The answer to this question is investigated by developing a new active hybrid polyoxometalate-based catalyst for asymmetric Diels-Alder reaction. Chirality transfer from the chiral anionic polyoxometalate to the covalently linked achiral imidazolidinone allows Diels-Alder cycloaddition products to be obtained with good yields and high enantioselectivities when using cyclopentadiene and acrylaldehydes as partners.
PRODUCTION METHOD OF EXO-TYPE NORBORNENE COMPOUND
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Paragraph 0024-0025, (2017/01/02)
PROBLEM TO BE SOLVED: To provide a production method of a norbornene compound, in particular, exo-enriched 2-acyl-5-norbornene containing many exo isomers, which is useful as a source material precursor of monomers for electronic materials and optical materials. SOLUTION: The production method of an exo-type norbornene compound is characterized by bringing an endo-type norbornene compound having an acyl group at a second position expressed by the formula below into contact with a tertiary amino compound (B) to carry out epimerization. The production method is carried out in a batch process where distillation purification is performed after the reaction or in a continuous process where purification is performed by reactive distillation. In the formula, R represents a hydrogen atom or an alkyl group or a phenyl group which may have a substituent. COPYRIGHT: (C)2015,JPOandINPIT
Carbocations as lewis acid catalysts in diels-alder and Michael addition reactions
Bah, Juho,Franzen, Johan
, p. 1066 - 1072 (2014/02/14)
In general, Lewis acid catalysts are metal-based compounds that owe their reactivity to a low-lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels-Alder reaction for a range of substrates. Catalyst loadings as low as 500 ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the substituents on the tritylium ion, the Lewis acidity of the catalyst could be tuned to control the outcome of the reaction. The ability of this carbocation as a Lewis acid catalyst was also further extended to the Michael reaction. Copyright
The potential of methylsiloxanes as solvents for synthetic chemistry applications
Ab Rani, Mohd Azri,Borduas, Nadine,Colquhoun, Victoria,Hanley, Robert,Johnson, Henry,Larger, Solene,Lickiss, Paul D.,Llopis-Mestre, Veronica,Luu, Selina,Mogstad, Martin,Oczipka, Philipp,Sherwood, James R.,Welton, Tom,Xing, Jun-Yi
, p. 1282 - 1296 (2014/03/21)
The potential use of volatile methylsiloxanes (VMSs) as solvents for chemicals synthesis has been explored. Assessment of the environmental impact of these VMS solvents is made and found to be significantly lower than those of the non-polar organic solvents that they have the potential to replace. The polarities of the VMSs, as expressed by empirical polarity measurements, and miscibilities with other liquids are found to be similar to those of alkane solvents. Finally, some uses of VMSs as solvents for both organic and inorganic transformations are described. The VMSs provide environmentally more sustainable (greener) alternatives to the nonpolar solvents that they have the potential to replace.
Application of electron-withdrawing coordinatively unsaturated η6-arene β-diketiminato-Ruthenium complexes in Lewis acid catalyzed Diels-Alder reactions
Schreiber, Dominique F.,Ortin, Yannick,Mueller-Bunz, Helge,Phillips, Andrew D.
experimental part, p. 5381 - 5395 (2011/12/13)
Utilizing the aza-Wittig reaction involving the ylid 3,5-(CF 3)2C6H3NPPh3 and 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, a highly fluorinated and electron-withdrawing β-diketiminate was obtained. Using strong bases, nBuLi, Ag2O, or TlOEt, the corresponding β-diketiminato-Li, -Ag, or -Tl chelated complexes were prepared. Subsequent in situ transmetalation with (Ru(η6-C6H6)Cl2) 2 or (Ru(η6-p-cymene)Cl2)2 afforded the half-sandwich chloro-substituted Ru(II) β-diketimino complexes in high yield. The synthesis of the Lewis acidic catalysts featuring a vacant coordination site at the metal center was accomplished using [Na]BArF (BArF = tetrakis[3,5-bis(trifluoromethyl)phenyl]boron). These complexes are active for the Lewis acid catalyzed Diels-Alder reaction between α,β-unsaturated aldehydes, that is, methacrolein, acrolein, and dienes, that is, cyclopentadiene and 2,3-dimethyl-1,3-butadiene, with conversions in the range of 66-98% under mild conditions. Whereas the herein described catalysts generally promote exo selectivity of the [4 + 2] cycloaddition between methacrolein and cyclopentadiene, the reaction involving acrolein shows predominantly the formation of the endo adduct, similar to that observed for the noncatalyzed reaction. Importantly, the coordinatively unsaturated complexes demonstrate moderate Lewis acidity, which allows for the controlled reaction between methacrolein and 2,3-dimethyl-1,3-butadiene to 1,3,4-trimethyl-3-cyclohexene-1- carboxaldehyde without further isomerization to the bicyclic ketone, which is in contrast to strong Lewis acidic catalysts based on transition metals or main-group elements reported in the literature.
