5455-72-1Relevant articles and documents
STRONGLY LEWIS ACIDIC METAL-ORGANIC FRAMEWORKS FOR CONTINUOUS FLOW CATALYSIS
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Paragraph 0201-0203; 0207; 0239; 0249, (2021/02/26)
Lewis acidic metal-organic framework (MOF) materials comprising triflate-coordinated metal nodes are described. The materials can be used as heterogenous catalysts in a wide range of organic group transformations, including Diels-Alder reactions, epoxide-ring opening reactions, Friedel-Crafts acylation reactions and alkene hydroalkoxylation reactions. The MOFs can also be prepared with metallated organic bridging ligands to provide heterogenous catalysts for tandem reactions and/or prepared as composites with support particles for use in columns of continuous flow reactor systems. Methods of preparing and using the MOF materials and their composites are also described.
Coupling Reaction between Aldehydes and Non-Activated Hydrocarbons via the Reductive Radical-Polar Crossover Pathway
Yahata, Kenzo,Sakurai, Shu,Hori, Shuhei,Yoshioka, Shin,Kaneko, Yuki,Hasegawa, Kai,Akai, Shuji
supporting information, p. 1199 - 1203 (2020/02/04)
Herein, we describe the generation of an organochromium-type carbanion species from a non-activated C-H bond and its nucleophilic addition to aldehydes. The catalytic carbanion generation occurred through formal deprotonation of a non-activated C-H bond under mild conditions and did not need the prefunctionalization or anion stabilizing group. Carbon radical intermediates generated by decatungstate photocatalyst-mediated hydrogen abstraction were captured by a chromium salt with the reductive radical-polar crossover reaction to produce organochromium carbanions.
Strongly Lewis Acidic Metal-Organic Frameworks for Continuous Flow Catalysis
Ji, Pengfei,Feng, Xuanyu,Oliveres, Pau,Li, Zhe,Murakami, Akiko,Wang, Cheng,Lin, Wenbin
supporting information, p. 14878 - 14888 (2019/10/02)
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.
Metal free chemoselective reduction of α-keto amides using TBAF as catalyst
Mamillapalli, N. Chary,Sekar, Govindasamy
, p. 61077 - 61085 (2015/02/19)
The metal and ligand free chemoselective reduction of the keto group and complete reduction of the both keto and amide groups of α-keto amide with hydrosilanes using tetrabutylammoniumflouride (TBAF) as catalyst have been accomplished. This methodology affords an efficient and economic route for the synthesis of biologically important α-hydroxy amides and β-amino alcohols. The other important advantage of this TBAF catalyst is chemoselective reduction of ketones to corresponding alcohols in the presence of several other sensitive functional groups.
Chemoselective reduction of α-keto amides using nickel catalysts
Mamillapalli, N. Chary,Sekar, Govidasamy
supporting information, p. 7881 - 7884 (2014/07/08)
Ni-catalysts are used for the first time to synthesize highly important α-hydroxy amides and β-amino alcohols from α-keto amides by chemoselective and complete reduction using hydrosilanes. Chemoselective complete reduction of α-keto amides in the presenc
Zinc tetrafluoroborate hydrate as a mild catalyst for epoxide ring opening with amines: Scope and limitations of metal tetrafluoroborates and applications in the synthesis of antihypertensive drugs (RS)/(R)/(S)-metoprolols
Pujala, Brahmam,Rana, Shivani,Chakraborti, Asit K.
experimental part, p. 8768 - 8780 (2011/12/04)
The scope and limitations of metal tetrafluoroborates have been studied for epoxide ring-opening reaction with amines, and Zn(BF4) 2?xH2O has been found to be a mild and efficient catalyst affording high yields under solvent-free conditions at rt with excellent chemo-, regio-, and stereoselectivities. The catalytic efficiency followed the order Zn(BF4)2?xH2O ? Cu(BF4)2?xH2O > Co(BF4) 2?6H2O ? Fe(BF4)2? 6H2O > LiBF4 for reactions with cyclohexene oxide and Zn(BF4)2?xH2O ? Co(BF4) 2?6H2O ? Fe(BF4)2? 6H2O > Cu(BF4)2?xH2O for stilbene oxide, but AgBF4 was ineffective. For reaction of styrene oxide with aniline, the metal tetrafluoroborates exhibited comparable regioselectivity (1:99-7:93) with preferential reaction at the benzylic carbon of the epoxide ring. A reversal of regioselectivity (91:1-69:31) in favor of the reaction at the terminal carbon of the epoxide ring was observed for reaction with morpholine. The regioselectivity was dependent on the electronic and steric factors of the epoxide and the pKa of the amine and independent of amine nucleophilicity. The role of the metal tetrafluoroborates is envisaged as "electrophile nucleophile dual activation" through cooperativity of coordination, charge-charge interaction, and hydrogen-bond formation that rationalizes the catalytic efficiency, substrate reactivity, and regioselectivity. The methodology was used for synthesis of cardiovascular drug metoprolol as racemic and enriched enantiomeric forms.
B2O3/Al2O3 as an efficient and recyclable catalyst for the synthesis of β-amino alcohols under solvent-free conditions
Zhang, Changfu,Chen, Jiuxi,Yu, Xiaochun,Chen, Xian,Wu, Huayue,Yu, Jianping
, p. 1875 - 1887 (2008/09/20)
A convenient and efficient procedure for the solvent-free synthesis of β-amino alcohols has been achieved via B2O3/Al2O3-promoted highly regioselective ring opening of epoxides with aromatic amines in good to excellent yields at room temperature. Addition
A facile preparation of ethanolamines by direct irradiation of some carbonyl compounds in N,N-dimethylaniline
Kim, Sung Sik,Mah, Yoon Jung,Kim, Ae Rhan
, p. 8315 - 8317 (2007/10/03)
Direct irradiation of some carbonyl compounds in N,N-dimethylaniline, without solvent, with 300 nm UV light afforded ethanolamines as the major product in moderate yields.
α-Nitrogenated organolithium compounds from α-amidomethyl and α-aminomethyl sulfones
Alonso, Diego A.,Alonso, Emma,Najera, Carmen,Ramon, Diego J.,Yus, Miguel
, p. 4835 - 4856 (2007/10/03)
Successive reaction of α-amidomethyl sulfones 7a,b, derived from primary amides, with n-butyllithium and primary alkyl bromides (CH2 = CHCH2Br, CH2 = CMeCH2Br, CH2 = CBrCH2Br, CH ≡ CCH
