cas 5453-80-5, 5-Norbornene-2-carboxaldehyde

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Method for preparing single-configuration C-2-position-monosubstituted norbornene derivative
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.
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(2021/07/01)

Bis-selenonium Cations as Bidentate Chalcogen Bond Donors in Catalysis
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.
He, Xinxin,Wang, Xinyan,Tse, Ying-Lung Steve,Ke, Zhihai,Yeung, Ying-Yeung
p. 12632 - 12642
(2021/10/21)

NOVEL BENZOIMIDAZOLES AS SELECTIVE INHIBITORS OF INDOLEAMINE 2, 3-DIOXYGENASES
Disclosed herein are novel benzoimidazoles and pharmaceutical compositions comprising at least one such novel benzoimidazoles, processes for the preparation thereof, and the method for using the same in therapy. In particular, disclosed herein are certain novel benzoimidazoles that are useful for inhibiting indoleamine 2, 3-dioxygenase and for treating diseases or disorders mediated thereby.
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Paragraph 0556; 0557

(2019/06/11)

Oxidative Dehomologation of Aldehydes with Oxygen as a Terminal Oxidant
A mild, efficient protocol for oxidative cleavage of C-C bonds in aldehydes has been developed that employs alkali metal hydrides as reagents and oxygen from air as a terminal oxidant. The method is applicable to a broad substrate range.
Shipilovskikh, Sergei A.,Rubtsov, Aleksandr E.,Malkov, Andrei V.
p. 6760 - 6762
(2017/12/26)

Improving the efficiency of the Diels-Alder process by using flow chemistry and zeolite catalysis
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.
Seghers,Protasova,Mullens,Thybaut,Stevens
supporting information
p. 237 - 248
(2017/08/14)

Ruthenium Lewis Acid-Catalyzed Asymmetric Diels–Alder Reactions: Reverse-Face Selectivity for α,β-Unsaturated Aldehydes and Ketones
Acrolein, methacrolein, methyl vinyl ketone, ethyl vinyl ketone, 3-methyl-3-en-2-one, and divinyl ketone were coordinated to a cationic cyclopentadienyl ruthenium(II) Lewis acid incorporating the electron-poor bidentate BIPHOP–F ligand. Analysis by NOESY and ROESY NMR techniques allowed the determination of conformations of enals and enones present in solution in CD2Cl2. The results were compared to solid-state structures and to the facial selectivities of catalytic asymmetric Diels–Alder reactions with cyclopentadiene. X-Ray structures of four Ru-enal and Ru-enone complexes show the α,β-unsaturated C=O compounds to adopt an anti-s-trans conformation. In solution, enals assume both anti-s-trans and anti-s-cis conformations. An additional conformation, syn-s-trans, is present in enone complexes. Enantioface selectivity in the cycloaddition reactions differs for enals and enones. Reaction products indicate enals to react exclusively in the anti-s-trans conformation, whereas with enones, the major product results from the syn-s-trans conformation. The alkene in s-cis conformations, while present in solution, is shielded and cannot undergo cycloaddition. A syn-s-trans conformation is found in the solid state of the bulky 6,6-dimethyl cyclohexanone-Ru(II) complex. The X-ray structure of divinyl ketone is unique in that the Ru(II) center binds the enone via a η2bond to one of the alkene moieties. In solution, coordination to Ru–C=O oxygen is adopted. A comparison of facial preference is also made to the corresponding indenyl Lewis acids.
Thamapipol, Sirinporn,Ludwig, Bettina,Besnard, Céline,Saudan, Christophe,Kündig, E. Peter
p. 774 - 789
(2016/10/17)

NOVEL 5 OR 8-SUBSTITUTED IMIDAZO [1, 5-a] PYRIDINES AS INDOLEAMINE AND/OR TRYPTOPHANE 2, 3-DIOXYGENASES
Disclosed herein are 5 or 8-substituted imidazo[l,5-a]pyridines and pharmaceutical compositions comprising at least one such 5 or 8-substituted imidazo[l,5-a]pyridines, processes for the preparation thereof, and the use thereof in therapy. Disclosed herein are certain 5 or 8- substituted imidazo[l,5-a]pyridines that can be useful for inhibiting indoleamine 2,3- dioxygenase and/or tryptophane 2,3-dioxygenase and for treating diseases or disorders mediated thereby.
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Paragraph 0491

(2016/10/31)

Method for preparing 5-norbornene-2-formaldehyde in microstructure reactor
The invention relates to a method for preparing 5-norbornene-2-formaldehyde in a microstructure reactor. 5-Norbornene-2-formaldehyde is generated through a Diels-Alder reaction of acrolein and cyclopentadiene in the microstructure reactor. Present industrial production technologies have the disadvantages of long reaction time and difficult removal of generated polymers adhered to a reaction device. The method for preparing 5-norbornene-2-formaldehyde in the microstructure reactor at a high temperature under a high pressure has the advantages of short reaction time and no generation of solids.
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Paragraph 0029; 0030

(2017/04/03)

Remote Tris(pentafluorophenyl)borane-Assisted Chiral Phosphoric Acid Catalysts for the Enantioselective Diels-Alder Reaction
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.
Hatano, Manabu,Ishihara, Hideyuki,Goto, Yuta,Ishihara, Kazuaki
p. 564 - 570
(2016/03/12)

PRODUCTION METHOD OF EXO-TYPE NORBORNENE COMPOUND
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
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Paragraph 0024-0025

(2017/01/02)

Chiral Dawson-Type Hybrid Polyoxometalate Catalyzes Enantioselective Diels-Alder Reactions
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.
Xuan, Wen-Jing,Botuha, Candice,Hasenknopf, Bernold,Thorimbert, Serge
supporting information
p. 16512 - 16516
(2015/11/09)

Enantioselective catalysts based on the chiral fragment (η5-C5Me5)Ir(Prophos) for Diels-Alder reactions
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.
Carmona, Daniel,Viguri, Fernando,Asenjo, Ainara,Lahoz, Fernando J.,García-Ordu?a, Pilar,Oro, Luis A.
p. 119 - 124
(2014/03/21)

Carbocations as lewis acid catalysts in diels-alder and Michael addition reactions
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
Bah, Juho,Franzen, Johan
p. 1066 - 1072
(2014/02/14)

The potential of methylsiloxanes as solvents for synthetic chemistry applications
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.
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)

Enantioselective diels-alder reactions with anomalous endo/exo selectivities using conformationally flexible chiral supramolecular catalysts
Swapped selectivities: The use of tailor-made catalysts results in anomalous endo/exo selectivities and high enantioselectivities in the Diels-Alder reactions of cyclopentadiene with different acroleins (see scheme). These supramolecular catalysts are prepared in situ from chiral diols, arylboronic acid, and tris(pentafluorophenyl)borane, and can discriminate the re/si face of the dienophile as well as the endo/exo approach of the diene.
Hatano, Manabu,Mizuno, Tomokazu,Izumiseki, Atsuto,Usami, Ryota,Asai, Takafumi,Akakura, Matsujiro,Ishihara, Kazuaki
scheme or table
p. 12189 - 12192
(2012/02/01)

Application of electron-withdrawing coordinatively unsaturated η6-arene β-diketiminato-Ruthenium complexes in Lewis acid catalyzed Diels-Alder reactions
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.
Schreiber, Dominique F.,Ortin, Yannick,Mueller-Bunz, Helge,Phillips, Andrew D.
experimental part
p. 5381 - 5395
(2011/12/13)

(η6-Arene) ruthenium(ii) complexes and metallo-papain hybrid as Lewis acid catalysts of Diels-Alder reaction in water
Covalent embedding of a (η6-arene) ruthenium(ii) complex into the protein papain gives rise to a metalloenzyme displaying a catalytic efficiency for a Lewis acid-mediated catalysed Diels-Alder reaction enhanced by two orders of magnitude in water.
Talbi, Barisa,Haquette, Pierre,Martel, Annie,De Montigny, Frederic,Fosse, Celine,Cordier, Stephane,Roisnel, Thierry,Jaouen, Gerard,Salmain, Michele
supporting information; experimental part
p. 5605 - 5607
(2010/08/21)

Erbium triflate in ionic liquids: A recyclable system of improving selectivity in Diels-Alder reactions
The efficiency of Er(OTf)3 in promoting the Diels-Alder reactions between different dienes and dienophiles in ionic liquids has been investigated. Compared with the analogous cycloadditions performed in conventional solvents shorter reaction times are required to obtain good/excellent yields. In most cases an enhancement of regio- and endo:exo selectivity was observed. The role of the ionic liquid, as a function of the cationic part, i.e. the imidazolium based or the pyridinium based, is discussed well. The ILs containing the catalyst can be readily separated from the reaction products and recovered in very high purity for direct reuse, up to six cycles.
Bortolini, Olga,De Nino, Antonio,Garofalo, Angelo,Maiuolo, Loredana,Procopio, Antonio,Russo, Beatrice
experimental part
p. 124 - 129
(2011/02/16)

Hydroxyl-containing monomer, polymer, resist composition, and patterning process
A hydroxyl-containing monomer of formula (1) is provided wherein R1 is H, F, methyl or trifluoromethyl, R2 and R3 are monovalent C1-C15 hydrocarbon groups, or R2 and R3 may form an aliphatic ring. The monomers are useful for the synthesis of polymers which have high transparency to radiation of up to 500 nm and the effect of controlling acid diffusion so that the polymers may be used as a base resin to formulate radiation-sensitive resist compositions having a high resolution.
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Page/Page column 40-41

(2009/10/01)

GENERATION OF ENDO- AND/OR EXO-NORBORNENECARBOXALDEHYDE AS AN INTERMEDIATE TO FUNCTIONALIZED NORBORNENES
Embodiments in accordance with the present invention provide for forming essentially pure diastereomers of 5/6-substituted norbornene-type monomers. Further, embodiments in accordance with the present invention encompass polymerizing such diastereomers to form addition or ROMP polymers where a desired exo-/endo-ratio of the diastereomers is provided to the polymerization, such ratio designed to provide a desired ratio of endo-/exo-structured repeating units for a resulting polymer to have desired physical or chemical properties.
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Page/Page column 10

(2009/05/28)

A Tin-tungsten mixed oxide as an efficient heterogeneous catalyst for C-C Bond Bond-Forming reactions
The tin-tungsten mixed oxide prepared by the calcination of the tin-tungsten hydroxide precursor with a Sn/W molar ratio of 2 at 800 °C (SnW2-800) acts as an effective and reusable solid catalyst for C-C bond-forming reactions, such as the cyclization of citronellal, the Diels-Alder reaction, and the cyanosilylation of carbonyl compounds with trimethylsilyl cyanide (TMSCN). Various kinds of structurally diverse aliphatic, aromatic, and unsaturated, heteroatom-containing substrates could be converted into the desired products in high to excellent yields. The observed catalyses for these reactions were truly heterogeneous and the recovered catalyst could be reused several times without an appreciable loss of its high catalytic performance. The Bronsted acid sites generated on the aggregated polytungstate species on SnW2-800 likely play an important role in the C-C bond-forming reactions.
Ogasawara, Yoshiyuki,Uchida, Sayaka,Yamaguchi, Kazuya,Mizuno, Noritaka
supporting information; experimental part
p. 4343 - 4349
(2009/11/30)

Effect of lewis acids on the Diels-Alder reaction in ionic liquids with different activation modes
The Diels-Alder reaction has been examined in room temperature ionic liquids with high molar concentrations of Lewis acids under various conditions. A molar ratio of 10% catalyst gave a large increase in the selectivity and the yield of the reaction. The effect of catalysts on reaction rates was also examined under 100 MPa of pressure which leads to modest improvements in reaction rates. Ultrasound and microwave dielectric heating were also shown to improve the rate and, to a minor extent, selectivity of the examined reactions. Copyright
Vidis, Ana,Kuesters, Ernst,Sedelmeier, Gottfried,Dyson, Paul J.
p. 264 - 270
(2008/09/20)

A rationalization of the solvent effect on the Diels-Alder reaction in ionic liquids using multiparameter linear solvation energy relationships
The Diels-Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) having different hydrogen bond acceptor abilities has been carried out in several ionic liquids and molecular solvents in order to obtain information about the factors affecting reactivity and selectivity. The solvent effects on these reactions are examined using multiparameter linear solvation energy relationships. The collected data provide evidence that the solvent effects are a function of both the solvent and the solute. For a solvent effect to be seen, the solute must have a complimentary character; selectivities and rates are determined by the solvent hydrogen bond donation ability (α) in the reactions of acrolein and methyl acrylate, but not of acrylonitrile. The Royal Society of Chemistry 2008.
Bini, Riccardo,Chiappe, Cinzia,Mestre, Veronica Llopsis,Pomelli, Christian Silvio,Welton, Thomas
experimental part
p. 2522 - 2529
(2009/02/02)

Enhanced Diels-Alder reactions: on the role of mineral catalysts and microwave irradiation in ionic liquids as recyclable media
This manuscript explores in detail the combined effect of solid supports or microwave irradiation in ionic liquids on a series of Diels-Alder reactions involving 1,3-cyclopentadiene and numerous dienophiles.
López, Ignacio,Silvero, Guadalupe,Arévalo, María José,Babiano, Reyes,Palacios, Juan?Carlos,Bravo, José Luis
p. 2901 - 2906
(2007/10/03)

High-pressure effects on the Diels-Alder reaction in room temperature ionic liquids
The effect of pressure on the Diels-Alder reaction was examined in room temperature ionic liquids, followed by high-pressure FT-IR spectroscopy using pressures up to ISOMPa. Pressure enhances the kinetic sensitivity of the reaction. The kinetic effect of fluorophobic interactions was examined using ionic liquids with fluorous cations. Ionic liquids in combination with ZnI 2 as a Lewis acid catalyst were also studied under high pressure. Copyright
Vidis, Ana,Laurenczy, Gabor,Kuesters, Ernst,Sedelmeier, Gottfried,Dyson, Paul J.
p. 109 - 114
(2007/10/03)

Imination reactions of free and coordinated 2-diphenylphosphino-1-phenyl- phospholane: Access to regioisomeric ruthenium(ii) complexes containing novel iminophosphorane-phosphine ligands
In this work, selective monoimination reactions of free and Ru-coordinated 2-diphenylphosphino-1-phenyl-phospholane with diphenylphosphoryl azide or 4-azido-2,3,5,6-tetrafluorobenzonitrile are described. Following this approach, a large variety of neutral and cationic mono- and dinuclear (η6- arene)-ruthenium(ii) complexes containing regioisomeric iminophosphorane- phosphine ligands could be prepared and, in some cases, structurally characterized by means of X-ray diffraction methods. The catalytic activity of these ruthenium complexes, both in racemic or enantiomerically pure form, in Diels-Alder cycloaddition reactions is also presented. the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
Diaz-Alvarez, Alba E.,Crochet, Pascale,Zablocka, Maria,Cadierno, Victorio,Duhayon, Carine,Gimeno, Jose,Majoral, Jean-Pierre
p. 1295 - 1306
(2007/10/03)

Triruthenium carbonyl clusters derived from chiral aminooxazolines: Synthesis and catalytic activity
Treatment of [Ru3(CO)12] with the chiral aminooxazolines (+)-2-amino-(4R)-phenyl-2-oxazoline (H2amphox), (+)-2-amino-(4R,5S)-indanyl-2-oxazoline (H2aminox) and (+)-2-(2′-anilinyl)-(4R,5S)-indanyl-2-oxazoline (H2aninox) in THF at reflux temperature, affords the complexes [Ru3(-H)( 3-κ2-Hox-N,N)(CO)9] (H2ox = H2amphox, 1; H2aminox, 2) and [Ru3(-H)(- κ2-Haninox-N,N)(CO)9] (3). In all cases, the activation of an N-H bond has occurred and the resulting amido fragment spans an edge of the metal triangle, while the N atom of the oxazoline ring is attached to the remaining metal atom (as in 1 and 2), or to one of the metal atoms of the bridged edge (as in 3). The use of 1-3 as catalyst precursors in the asymmetric hydrogen-transfer reduction of acetophenone and in the asymmetric cycloaddition of cyclopentadiene and acroleine is reported. The Royal Society of Chemistry 2006.
Cabeza, Javier A.,Da Silva, Ivan,Del Rio, Ignacio,Gossage, Robert A.,Miguel, Daniel,Suarez, Marta
p. 2450 - 2455
(2007/10/03)

Bis-phosphine monoxide platinum(II) and palladium(II) cationic complexes as Lewis acid catalysts in Diels-Alder and sulfoxidation reactions
A series of bis-phosphine monoxide (BPMO) palladium(II) and platinum(II) cationic complexes of the type [M(BPMO-κ2-P,O)2][X]2 (M = Pd, Pt; BPMO = Ph2P-(CH2)n-P(O)Ph2 with n = 1 (dppmO), 2 (dppeO), 3 (dpppO); X = BF4, TfO) were prepared from the corresponding chlorides [MCl2(BPMO-κ1-P)2] upon treatment with 2 equiv. of AgX in wet acetone/CH2Cl2 or MeOH solutions. They were characterized by 1H and 31P{1H} NMR spectroscopies and, in the case of the complex [Pt(dppeO-κ2-P,O)2][BF4]2, also by X-ray crystallography. These complexes were tested as catalysts in some Diels-Alder and oxidation reactions with different substrates. In the latter reaction Pt(II) complexes showed moderate activity, while for the former one, both classes of complexes were active in the C-C coupling, in particular the Pt(II) species showed interesting high endo/exo diasteroselectivity depending on the counteranion.
Sgarbossa, Paolo,Pizzo, Erika,Scarso, Alessandro,Sbovata, Silvia Mazzega,Michelin, Rino A.,Mozzon, Mirto,Strukul, Giorgio,Benetollo, Franco
p. 3659 - 3666
(2007/10/03)

exo-selective asymmetric Diels-Alder reaction catalyzed by diamine salts as organocatalysts
A novel binaphthyl-based diamine (R)-2 was designed and synthesized. A protonic acid-(R)-2 salt catalyst has the advantage of exhibiting unprecedented high exo selectivity in the asymmetric Diels-Alder reaction of α,/β-unsaturaled aldehydes. For instance, the reaction between cinnamaldehyde and cyclopentadiene in the presence of 12 mol % of binaphthyl-based diamine (R)-2 and 10 mol % of P-TsOH·H2O in α,α,α-trifluorotoluene at -20 °C gave the corresponding exo cycloadduct with 92% ee as a major diastereomer (exolendo = 13/1).
Kano, Taichi,Tanaka, Youhei,Maruoka, Keiji
p. 2687 - 2689
(2007/10/03)

An in-depth look at the effect of Lewis acid catalysts on Diels-Alder cycloadditions in ionic liquids
The present work explores in detail the Diels-Alder reaction between cyclopentadiene and a series of dienophiles, performed in an innovative medium such as an ionic liquid. The potential activation of different Lewis acid catalysts and their load effect when used in combination with this solvent have been explored, in order to settle the improvement on rates and selectivities.
Silvero, Guadalupe,Arévalo, María José,Bravo, José Luis,ávalos, Martín,Jiménez, José Luis,López, Ignacio
p. 7105 - 7111
(2007/10/03)

Recyclable organotungsten Lewis acid and microwave assisted Diels-Alder reactions in water and in ionic liquids
The water-soluble, organotungsten Lewis acid, [OP(2-py)3W(CO) (NO)2](BF4)2 (1), was synthesized and characterized. A series of 1-catalyzed Diels-Alder reactions were investigated under conventional heating or microwave heating conditions. The cycloaddition reactions were efficiently conducted in either water or in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate. The ionic liquid acts as a powerful medium not only for rate- and selectivity enhancements but also for facilitating catalyst recycling. Dramatic rate acceleration via microwave flash heating as compared to thermal heating was observed. Graphical Abstract
Chen, I-Hon,Young, Jun-Nan,Yu, Shuchun Joyce
p. 11903 - 11909
(2007/10/03)

Planar chiral PHANOLs as double hydrogen bonding donor organocatalysts: Synthesis and catalysis
4,12-Dihydroxy[2.2]paracyclophanediol (PHANOL; 1), and its para-substituted derivatives 2, 5 and 7, were found to catalyse Diels-Alder cyclo-additions of α,β-unsaturated aldehydes or ketones with dienes and/or epoxide ring opening reactions with amines. The mode of catalysis by the PHANOLs is via double hydrogen bonding to the two sp2 lone pairs of a carbonyl group or the two lone pairs of the epoxide. The order of activity of the PHANOLs for catalysis of the Diels-Alder reaction essentially correlates with the expected hydrogen-bond donor strength based on the degree of electron-withdrawing capability of the group(s) in the para position. In contrast, ortho-substituted PHANOLs 10, 11 and 14 were not active as catalysts due to steric interference with the double hydrogen bonding mode. 1H NMR and IR spectral data for the various PHANOLs are discussed in support of the proposed double hydrogen bond mode.
Braddock, D. Christopher,MacGilp, Iain D.,Perry, Benjamin G.
p. 1117 - 1130
(2007/10/03)

Iminium ion catalysis: Use of the α-effect in the acceleration of the Diels-Alder reaction
The α-effect can be used in the acceleration of the DielsAlder reaction between a series of dienes and electron deficient dienophiles using iminium ion catalysis, providing a novel molecular scaffold capable of performing this class of catalytic process.
Cavill, Julie L.,Peters, Jens-Uwe,Tomkinson, Nicholas C. O.
p. 728 - 729
(2007/10/03)

Planar chiral PHANOLS as organocatalysts for the Diels-Alder reaction via double hydrogen-bonding to a carbonyl group
Planar chiral PHANOLs have been shown to catalyze Diels-Alder reactions of α,β-unsaturated aldehydes and ketones with various dienes. Rate accelerations of up to ca. 30-fold were obtained using the electron deficient 4,12-dihydroxy-7,15-dinitro[2.2]paracyclophane as a catalyst. It is proposed that the carbonyl group of the dienophile is activated via a double hydrogen-bonding mode. Although the PHANOLs are inherently chiral, little or no asymmetric induction was observed when using enantiopure (R)-PHANOL.
Braddock, D. Christopher,MacGilp, Iain D.,Perry, Benjamin G.
p. 1121 - 1124
(2007/10/03)

I2 as an efficient catalyst in ionic Diels-Alder reactions of α,β-unsaturated acetals
A variety of protected and unprotected α,β-unsaturated aldehydes react with 1,3-dienes in the presence of I2 to give the corresponding cycloadducts.
Chavan, Subhash P.,Sharma, Pallavi,Rama Krishna,Thakkar, Mahesh
p. 3001 - 3003
(2007/10/03)

Hydroxyapatite-bound cationic ruthenium complexes as novel heterogeneous Lewis acid catalysts for Diels-Alder and aldol reactions
Creation of a stable and well-defined active center on a solid surface is a promising protocol for designing more efficient hybrid-catalysts that bridge the gap between homogeneous and heterogeneous catalysis. Treatment of a hydroxyapatite-bound Ru complex (RuHAP) with an aqueous solution of AgX (X = SbF6-, TfO-) afforded a new type of cationic Ru phosphate complex, having potentially vacant coordination sites. These cationic RuHAPs exhibited Lewis acidity toward carbonyl and cyano groups, promoting Diels-Alder and Aldol reactions with high efficiencies. Moreover, no Ru leaching was detected in the above organic reactions, and then the catalysts were recyclable. Copyright
Mori, Kohsuke,Hara, Takayoshi,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
p. 11460 - 11461
(2007/10/03)

Divergent synthesis of two precursors of 3′-homo-2′-deoxy- and 2′-homo-3′-deoxy-carbocyclic nucleosides
Aminocyclopentanedimethanols 4 and 5, which are of interest for the synthesis of higher homologues of 2′-deoxy- and 3′-deoxycarbonucleosides, respectively, were efficiently prepared by divergent routes starting from (±)-exo-bicyclo[2.2.1]hept-5-ene-2-carbaldehyde. In the key step, ammonolysis of the common intermediate (±)-(1β,3β,4α)-4-benzoyloxymethyl-1,3- cyclopentanedicarboxylic anhydride and subsequent esterification afford near-equimolar amounts of two easily separable isomeric carbamoyl esters.
Blanco, José M,Fernández, Franco,García-Mera, Xerardo,Rodríguez-Borges, José E
p. 8843 - 8849
(2007/10/03)

Enantioselective Diels-Alder reactions with N-hydroxy-N-phenylacrylamide
Matrix presented The use of hydroxamic acids as templates for Lewis acid catalyzed enantioselective Diels-Alder reactions has been examined. A very simple chiral Lewis acid, prepared by mixing optically pure binaphthol with 3 equiv of trimethylaluminum, catalyzes the [4 + 2] cycloaddition of N-hydroxy-N-phenylacrylamide with cyclopentadiene at 0°C in high yield (>96%) and with a fairly good level of enantioselectivity (91% ee). Facile conversion of the products to the corresponding alcohols or aldehydes makes the hydroxamic acid intermediates particularly useful.
Corminboeuf, Olivier,Renaud, Philippe
p. 1731 - 1733
(2007/10/03)

Highly efficient enantioselective catalysis in supercritical carbon dioxide using the perfluoroalkyl-substituted ligand (R,S)-3-H2F6-BINAPHOS
Perfluoroalkyl-substitution of the aryl groups in the BINAPHOS skeleton was achieved using a synthetic strategy based on the Cu(I)-catalyzed cross coupling of arylmagnesium bromide and F(CF2)6(CH2)2I. The rhodium complexes of the new ligand (R,S)-3-H2F6-BINAPHOS (10) exhibited spectroscopic properties and reactivities similar to those of the unsubstituted parent compounds. The substitution provided a high affinity of the ligand and its complexes for scCO2 allowing the development of ecologically benign protocols for catalytic asymmetric synthesis and even the spectroscopic detection of catalytically active intermediates. Using this new system, a large variety of substrates were hydroformylated in scCO2 with rates and enantioselectivities comparable to those of the parent system in benzene solution. At the same time, the CO2-philic substitution pattern resulted in a significantly higher regioselectivity towards the desired chiral aldehydes. Preliminary results indicated for the first time also a remarkable potential of BINAPHOS-derived ligands for asymmetric hydrogenation reactions. The possibility to develop new work-up schemes for product purification and/or catalyst immobilisation based on scCO2 as the only medium for catalysis and extraction (CESS process) was experimentally verified using a rhodium catalyst containing 10.
Franciò, Giancarlo,Wittmann, Klaus,Leitner, Walter
p. 130 - 142
(2007/10/03)

Aluminum trisphenoxide polymer as a Lewis acidic, solid catalyst
A newly introduced, solid polymer of an aluminum trisphenoxide has been demonstrated an efficient catalyst for promoting the Diels-Alder reaction of α,β-enals.
Saito, Susumu,Murase, Masaaki,Yamamoto, Hisashi
p. 57 - 58
(2007/10/03)

Application of arylboron difluoride Lewis acid catalysts to the Diels- Alder reaction: Convenient, non-volatile alternatives to boron trifluoride
Comparative studies were carded out on boron trifluoride etherate, phenylboron difluoride and meta-nitrophenylboron difluoride for the Lewis acid catalysed Diels-Alder reaction of cyclopentadiene and a range of standard dienophiles in tetrahydrofuran solution. Phenylboron difluoride showed remarkably similar reactivity in terms of yield and endo to exo selectivity to boron trifluoride, whereas meta-nitrophenylboron difluoride was more reactive than either boron trifluoride or phenylboron difluoride and showed more marked differences in endo: exo ratios. These results contrast to some extent with gas-phase semi-empirical calculations (PM3), which suggest that boron trifluoride and meta-nitrophenylboron difluoride should have similar reactivity; phenylboron difluoride being less reactive. However, since arylboron difluorides are easily prepared, these Lewis acids represent a group of potentially highly tuneable catalysts for Diels-Alder reactions.
De La Torre, Maria Fe,Caballero, M. Cruz,Whiting, Andrew
p. 8547 - 8554
(2007/10/03)

Homogeneous Diels-Alder catalysis by organotungsten Lewis acid containing tris(2-pyridyl)phosphine ligand
The complex [P(2-py)3W(CO)(NO)2](BF4)2 (1) is an excellent catalyst precursor for Diels-Alder reactions of 1,3-diene and α,β-unsaturated ketones and/or aldehydes with a catalyst loading as low as 0.3 mol%.
Kuo, Cheng-Yi,Fuh, Yaw-Shyan,Chaen, Ming-Cheng,Yu, Shuchun Joyce
p. 6451 - 6454
(2007/10/03)

Dilithium 2,2'-methylenebis(4,6-di-tert-butylphenoxide) as a bidentate Lewis acid in organic synthesis
Dilithium 2,2'-methylenebis(4,6-di-tert-butylphenoxide) can be successfully utilized as a bidentate Lewis acid for simultaneous coordination to carbonyl groups, thereby accelerating the Diels-Alder reactions. The double activation ability of the bidentate lithium reagent toward carbonyls is emphasized in comparison with the corresponding monodentate lithium reagent.
Ooi, Takashi,Saito, Akira,Maruoka, Keiji
p. 3745 - 3748
(2007/10/03)

A new chiral ligand for the Fe-Lewis acid catalysed asymmetric Diels-Alder reaction
The readily accessible enantiopure hydrobenzoin forms the backbone of the new bidentate ligand BIPHOP-F that is shown here to provide the chiral environment for a highly enantioselective Fe-Lewis acid catalysed Diels-Alder reaction between α,β-enals and dienes.
Bruin, Marion E.,Peter Kuendig
p. 2635 - 2636
(2007/10/03)

A cationic palladium(II) complex-catalyzed diels-alder reaction
A cationic palladium(II) complex, [PdL2(RCN)2](BF4)2, has been found to catalyze the Diels-Alder reaction of α, β-unsaturated carbonyl compounds with dienes, affording the corresponding cycloadducts in good yields. Excellent enanlioselectivity can be achieved in the reaction of N- acryloyloxazolidinone and cyclopentadiene by use of a chiral ligand, BINAP.
Oi, Shuichi,Kashiwagi, Kenji,Inoue, Yoshio
p. 6253 - 6256
(2007/10/03)

Indium trichloride (InCl3) catalysed Diels-Alder reaction in water
Indium trichloride (InCl3) is found to catalyse the Diels-Alder reaction in water; the catalyst can be easily recovered from water after the reaction is completed and can be reused.
Loh, Teck-Peng,Pei, Jian,Lin, Mei
p. 2315 - 2316
(2007/10/03)

Homogeneous Catalysis: Use of Chiral Titanocene Complexes for Asymmetric Catalytic Diels-Alder Reactions
A stable, chiral diaquo titanocene complex is an excellent catalyst for certain Diels-Alder reactions giving good enantioselectivity which indicates that catalysis occurs by metal rather than by proton activation of the dienophile.
Odenkirk, William,Bosnich, B.
p. 1181 - 1182
(2007/10/02)

Synthesis of dipeptides containing α-substituted amino acids; their use as chiral ligands in Lewis-acid-catalyzed reactions
L-α-Methylphenylalanine, obtained by enzymatic resolution of the corresponding racemic amide with amidase from Ochrobactrum anthropi NCIMB 40321, was used in the synthesis of dipeptides containing α-substituted amino acids.The 2-hydroxynaphthalene-1-carboxaldehyde Schiff bases of the dipeptides (1 and 2) were tested as Ti(IV) and Al(III) complexes in asymmetric Lewis-acid-catalyzed reactions.Only the Al(III) complex of 2 showed moderate enantioselectivity in the cyanation reaction of benzaldehyde with TMS-CN.
Kaptein, Bernard,Monaco, Vania,Broxterman, Quirinus B.,Schoemaker, Hans E.,Kamphuis, Johan
p. 231 - 238
(2007/10/02)

Diiodosamarium, a Catalyst Precursor for Diels-Alder and Hetero Diels-Alder Reactions.
SmI2 presents catalytic activity for Diels-Alder reactions between cyclopentadiene or isoprene and various dienophiles, and for hetero Diels-Alder reactions.
Weghe, Pierre Van de,Collin, Jacqueline
p. 2545 - 2548
(2007/10/02)

Chiral Lewis acids derived from 1,8-naphthalenediylbis(dichloroborane)
Chiral Lewis acids derived from 1,8-Naphthalenediylbis(dichloroborane), a novel bidentate Lewis acid, have been found to be active catalysis for the asymmetric Diels-Alder reaction. Utilizing chiral ligands derived from amino acids and diols, a range of enantioselectivities have been achieved with cyclopentadiene and various α,β-unsaturated aldhydes.
Reilly, Michael
p. 7209 - 7212
(2007/10/02)