128441-66-7

Upstream product

• 78-94-4 methyl vinyl ketone 
• 1165952-91-9 cyclohexa-1,3-diene 

Downstream Products

• 2716-23-6 bicyclo[2.2.2]octan-2-one 

Relevant academic research and scientific papers

Scandium trifluoromethanesulfonate (Sc(OTf)3). A novel reusable catalyst in the Diels-Alder reaction

Scandium trifluoromethanesulfonate (Sc(OTf)3) is found to be quite effective as a Lewis acid catalyst in the Diels-Alder reaction. The novel catalyst is available in both aqueous and organic media, is easily recovered from aqueous layer after the reaction is completed, and can be reused.

Syntheses and chemistry of Tris(2-pyridyl)phosphine complexes of Group VI transition metals. X-ray structural studies of the molybdenum complexes

Treatment of P(2-py)3 with Mo(CO)6 or M(CO)3(CH3CN)3 (M=Cr, W) in CH3CN affords compounds of the type P(2-py)3M(CO)3 (1a, M=Cr; 1b, M=Mo; 1c, M=W). Complex P(2-py)3Mo(CO)3·CH2Cl2 was structurally characterized, and its ORTEP drawing shows an almost perfect octahedral arrangement around the Mo center, and the P(2-py)3 ligand occupying the facial position of the octahedron through the coordination of three pyridyl nitrogen atoms. Substitution of CO ligands can take place when treating compounds 1b and 1c with one or two equiv. of NOBF4 in CH3NO2 solvent to afford [P(2-py)3M(CO)3-n(NO)n](BF4) n (2a, M=Mo, n=1; 2b, M=W, n=1; 3a, M=Mo, n=2; 3b, M=W, n=2). These singly and doubly charged cationic species have been characterized by 1H-, 13C-, 31P-, 19F-NMR and IR spectroscopy, as well as elemental analysis. The CO lability of 3a and 3b generated the 16-electron species, [P(2-py)3M(NO)2]2+, which binds to most Lewis basic donor ligands to give complexes of the type, [P(2-py)3M(L)(NO)2](BF4)2 (L=nitriles, aldehydes). A single crystal of [P(2-py)3M(CH3CH2CN)(NO)2](BF 4)2·CH3NO2 was also isolated and structurally characterized. The crystallographic analysis indicated an octahedral arrangement about the Mo metal center. The 1H-NMR downfield shift of the metal-coordinated crotonaldehyde in compounds 4c and 5c is used as a qualitative measurement of relative Lewis acidity, and the acid strength of [P(2-py)3M(NO)2]2+ is comparable to that of TiCl4 when M=Mo and to BF3 and AlCl3 when M=W. The Diels-Alder reactions between cyclohexadienes and methyl vinyl ketone were catalyzed by 0.3 mol% of [P(2-py)3W(CO)(NO)2](BF4)2 (3b) to afford an average 94% conversion and 83% isolated yield.

Scandium perfluoroalkanesulfonate-catalyzed Diels-Alder reactions in an organic solvent

Scandium perfluoroalkanesulfonate-catalyzed Diels-Alder reactions proceeded smoothly in dry dichloromethane in the presence of molecular sieves (MS) 5 ?. It was found that water interfered with the reactions, contrary to most rare earth-catalyzed reactions that proceed smoothly in aqueous media. Among scandium perfluoroalkanesulfonates tested, scandium triflate (Sc(OTf)3), scandium pentafluoroethanesulfonate (Sc(OSO2C2F5)3), and scandium nonafluorobutanesulfonate (Sc(OSO2C4F9)3) gave the highest yields and selectivities.

Unexpected fragmentations leading to quinanes and hydrindanes mediated by a silyl radical

Useful bicyclic ring systems are obtained by tris-trimethylsilylsilyl radical (TMS3Si·) mediated fragmentation of strained alkene precursors.

Iodine-Catalyzed Diels-Alder Reactions

The Diels-Alder cycloaddition is the most popular pericyclic reaction with numerous applications in synthesis and catalysis. We now demonstrate that we can perform this reaction under mild and metal-free conditions relying on molecular iodine as the catalyst. Cycloadditions with cyclohexadiene, cyclopentadiene, or isoprene with various dienophiles can be performed typically within minutes in moderate to good yields and high endo selectivity. The mechanistic studies including kinetic and DFT investigations clearly indicate a halogen-bond activation and rule out other modes of activation. Furthermore, iodine performs equally well as typical metallic Lewis acids like AlCl3, SnCl4, or TiCl4.

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.

Strongly Lewis Acidic Metal-Organic Frameworks for Continuous Flow Catalysis

The synthesis of highly acidic metal-organic frameworks (MOFs) has attracted significant research interest in recent years. We report here the design of a strongly Lewis acidic MOF, ZrOTf-BTC, through two-step transformation of MOF-808 (Zr-BTC) secondary building units (SBUs). Zr-BTC was first treated with 1 M hydrochloric acid solution to afford ZrOH-BTC by replacing each bridging formate group with a pair of hydroxide and water groups. The resultant ZrOH-BTC was further treated with trimethylsilyl triflate (Me3SiOTf) to afford ZrOTf-BTC by taking advantage of the oxophilicity of the Me3Si group. Electron paramagnetic resonance spectra of Zr-bound superoxide and fluorescence spectra of Zr-bound N-methylacridone provided a quantitative measurement of Lewis acidity of ZrOTf-BTC with an energy splitting (?E) of 0.99 eV between the ?x? and ?y? orbitals, which is competitive to the homogeneous benchmark Sc(OTf)3. ZrOTf-BTC was shown to be a highly active solid Lewis acid catalyst for a broad range of important organic transformations under mild conditions, including Diels-Alder reaction, epoxide ring-opening reaction, Friedel-Crafts acylation, and alkene hydroalkoxylation reaction. The MOF catalyst outperformed Sc(OTf)3 in terms of both catalytic activity and catalyst lifetime. Moreover, we developed a ZrOTf-BTC?SiO2 composite as an efficient solid Lewis acid catalyst for continuous flow catalysis. The Zr centers in ZrOTf-BTC?SiO2 feature identical coordination environment to ZrOTf-BTC based on spectroscopic evidence. ZrOTf-BTC?SiO2 displayed exceptionally high turnover numbers (TONs) of 1700 for Diels-Alder reaction, 2700 for epoxide ring-opening reaction, and 326 for Friedel-Crafts acylation under flow conditions. We have thus created strongly Lewis acidic sites in MOFs via triflation and constructed the MOF?SiO2 composite for continuous flow catalysis of important organic transformations.

Borenium ionic liquids as catalysts for Diels-Alder reaction: Tuneable Lewis superacids for catalytic applications

Ionic liquids based on the tricoordinate borenium cation were used for the first time as Lewis acid catalysts for a model Diels-Alder reaction. The conversion of the dienophile was successfully correlated with the Gutmann acceptor number values of the ionic liquids. Borenium ionic liquids exceeded the performance of catalysts reported in the literature.

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

Silylium ion-catalyzed challenging Diels-Alder reactions: The danger of hidden proton catalysis with strong Lewis acids

The pronounced Lewis acidity of tricoordinate silicon cations brings about unusual reactivity in Lewis acid catalysis. The downside of catalysis with strong Lewis acids is, though, that these do have the potential to mediate the formation of protons by various mechanisms, and the thus released Bronsted acid might even outcompete the Lewis acid as the true catalyst. That is an often ignored point. One way of eliminating a hidden proton-catalyzed pathway is to add a proton scavenger. The low-temperature Diels-Alder reactions catalyzed by our ferrocene-stabilized silicon cation are such a case where the possibility of proton catalysis must be meticulously examined. Addition of the common hindered base 2,6-di-tert-butylpyridine resulted, however, in slow decomposition along with formation of the corresponding pyridinium ion. Quantitative deprotonation of the silicon cation was observed with more basic (Mes)3P to yield the phosphonium ion. A deuterium-labeling experiment verified that the proton is abstracted from the ferrocene backbone. A reasonable mechanism of the proton formation is proposed on the basis of quantum-chemical calculations. This is, admittedly, a particular case but suggests that the use of proton scavengers must be carefully scrutinized, as proton formation might be provoked rather than prevented. Proton-catalyzed Diels-Alder reactions are not well-documented in the literature, and a representative survey employing TfOH is included here. The outcome of these catalyses is compared with our silylium ion-catalyzed Diels-Alder reactions, thereby clearly corroborating that hidden Bronsted acid catalysis is not operating with our Lewis acid. Several simple-looking but challenging Diels-Alder reactions with exceptionally rare dienophile/enophile combinations are reported. Another indication is obtained from the chemoselectivity of the catalyses. The silylium ion-catalyzed Diels-Alder reaction is general with regard to the oxidation level of the α,β-unsaturated dienophile (carbonyl and carboxyl), whereas proton catalysis is limited to carbonyl compounds.