136655-70-4Relevant articles and documents
DABCO-based chiral ionic liquids as recoverable and reusable organocatalyst for asymmetric Diels–Alder reaction
Aalam, Mohd Jubair,Deepa,Chaudhary, Pooja,Meena, Dhan Raj,Yadav, Geeta Devi,Singh, Surendra
supporting information, p. 134 - 146 (2021/11/16)
New DABCO-based chiral ionic liquids were synthesized and evaluated in asymmetric Diels–Alder reaction of cyclopentadiene with α,β-unsaturated aldehydes or 4-phenyl-3-buten-2-one. Chiral ionic liquid of modified MacMillan catalyst having a DABCO cation and hexafluorophosphate anion acts as organocatalyst (5?mol%) for the Diels–Alder reaction of crotonaldehyde and cyclopentadiene producing 98% of the product and 87% ee (endo) in CH3CN/H2O (95/5) at 25°C in 2?h. The scope and limitations of the catalysis were also studied by using cyclopentadiene and α,β-unsaturated aldehydes, and the Diels–Alder products were obtained in 18%–92% yields with 68%–93% ee. The catalyst was recycled and reused up to 6 cycles with a slight drop in ee and conversion of the product.
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.
Application of recyclable ionic liquid-supported imidazolidinone catalyst in enantioselective Diels-Alder reactions
Shen, Zhi-Liang,Cheong, Hao-Lun,Lai, Yin-Chang,Loo, Wan-Yi,Loh, Teck-Peng
supporting information, p. 2626 - 2630 (2013/02/22)
The application of ionic liquid-supported imidazolidinone catalyst I in enantioselective Diels-Alder reactions was investigated. The Diels-Alder reactions involving α,β-unsaturated aldehydes and cyclopentadiene proceeded efficiently in the presence of cat
Micellar-driven substrate selectivity in Cr(salen)Cl catalytic Diels-Alder reaction in water
Trentin, Francesco,Scarso, Alessandro,Strukul, Giorgio
supporting information; experimental part, p. 6978 - 6981 (2012/02/13)
A 3.5 increase in catalytic activity was observed in the Cr(III) (salen)Cl 3 catalyzed Diels-Alder reaction between cyclopentadiene 1 with the longer trans-2-decenal 2g compared to the shorter trans-2-butenal 2a dienophile under aqueous micellar conditions, while in chloroform the two substrates react with comparable activities.
Synthesis of cis-Hedione and methyl jasmonate via cascade Baylis-Hillman reaction and Claisen ortho ester rearrangement
Chapuis, Christian,Buechi, George H.,Wueest, Hans
, p. 3069 - 3088 (2007/10/03)
The exocyclically unsaturated conjugated keto esters 10, obtained via a Claisen ortho ester rearrangement of the allylic hydroxy ketones 9, were either directly hydrogenated or partially isomerized into the endocyclically unsaturated tetrasubstituted didehydrojasmonoid intermediates 14, prior to a more selective hydrogenation with Pd/C in cyclohexane to the disubstituted oxocyclopentaneacetates 15 (Scheme 2). The key intermediates 9 were obtained either by a four-step sequence, including acetal protection/deprotection from enone 1, in the specific case of hydroxy ketone 9a (Scheme 1), or more directly and generally by a Baylis-Hillman reaction from cyclopent-2-en-1-one (16) and the appropriate aldehydes 17 (Scheme 2). The judicious choice of these aldehydes opens versatile modifications for the stereoselective introduction of the partially cis- or epimerized trans-C(2) jasmonoid side chain, while the Baylis-Hillman reaction, catalyzed by chiral [1,1′-binaphthalene]-2, 2′-diols (BINOLs) 19 (Scheme 3), may be efficiently conducted in a one-pot cascade fashion including the ortho ester Claisen rearrangement.
Design of bronsted acid-assisted chiral Lewis acid (BLA) catalysts for highly enantioselective Diels-Alder reactions
Ishihara, Kazuaki,Kurihara, Hideki,Matsumoto, Masayuki,Yamamoto, Hisashi
, p. 6920 - 6930 (2007/10/03)
Bronsted acid-assisted chiral Lewis acid (BLA) was highly effective as a chiral catalyst for the enantioselective Diels-Alder reaction of both α- substituted and α-unsubstituted α,β-enals with various dienes. Hydroxy groups in optically active binaphthol derivatives and boron reagents with electron-withdrawing substituents were used as Bronsted acids and Lewis acids, respectively. Intramolecular Bronsted acids in a chiral BLA catalyst played an important role in accelerating the rate of Diels-Alder reactions and in producing a high level of enantioselectivity. In particular, excellent enantioselectivity was achieved due to intramolecular hydrogen bonding interaction and attractive π-π donor-acceptor interaction in the transition-state assembly by hydroxy aromatic groups in a chiral BLA catalyst.
Aqueous catalysis: Methylrhenium trioxide (MTO) as a homogeneous catalyst for the Diels-Alder reaction
Zhu, Zuolin,Espenson, James H.
, p. 3507 - 3512 (2007/10/03)
The title compound proves to be an effective and efficient catalyst for the Diels-Alder reaction when the dienophile is an α,β-unsaturated ketone or aldehyde. It is especially effective in water. Equal amounts of any such dienophile and any of six representative dienes (isoprene, 2-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, cyclopentadiene, 1,2,3,4,5-pentamethylcyclopentadiene, and 1,3-cyclohexadiene) were used, along with 1% MTO. The reactions gave usually > 90% isolated yield of the cycloaddition product except for the larger dienophiles. Nearly exclusively, there was formed one product isomer, the same one that usually predominates. The reactions were often run in chloroform (mostly) and in other organic solvents. A select number were carried out in water, where the reactions gave a greater product yield in a considerably shorter time. Water, itself, is known to enhance the rates of Diels-Alder reactions, but MTO exerts an additional accelerating effect. Kinetics studies were carried out to show that the rate is proportional to the catalyst concentration. The products do not inhibit the reaction. The desirability of MTO as a Diels-Alder catalyst stems from a combination of favorable properties: the inertness to air/oxygen, the tolerance for many substrates, the use of an aqueous medium, and the absence of product inhibition. The initial step appears to be the (weak) coordination of the carbonyl oxygen to the electropositive rhenium center. Steric crowding around rhenium inhibits reactions of the larger dienophiles.
