- Synthesis of cinnamyl benzoate over novel heteropoly acid encapsulated ZIF-8
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ZIF-8 is a zeolitic imidazolate framework which is a subclass of metal organic framework (MOF). ZIF-8 is the emerging class of MOF with various applications. Dodecatungstophosphoric acid (DTP) encapsulated ZIF-8 was prepared first time using bottle around the ship strategy. This approach covers ZIF-8 synthesis along with DTP encapsulation in one pot synthesis. The synthesized catalyst shows highest catalytic activity for esterification reaction of benzoic anhydride with cinnamyl alcohol to form cinnamyl benzoate. Heterogeneous catalytic synthesis of cinnamyl benzoate with complete reaction kinetics is presented here for the first time. Cinnamyl benzoate is a famous perfumery and flavoring agent and GRAS listed food additive molecule. Catalyst preparation method is simple, rapid and can be done at room temperature using water as a solvent. DTP@ZIF-8 shows sodalite like structure and it was confirmed by applying several characterization techniques like SEM, TEM, XRD, BET, FTIR, TGA and ammonia-TPD. Duration of DTP@ZIF-8 crystal formation was studied and optimized up to 12 h. Catalyst is thermally stable up to 400 °C and showed reusability for 3 cycles. Reaction kinetics was studied with best fit of Eley-Rideal mechanism.
- Malkar, Radhika S.,Yadav, Ganapati D.
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- Superior activity and selectivity of multifunctional catalyst Pd-DTP@ZIF-8 in one pot synthesis of 3-phenyl propyl benzoate
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The catalytic efficiency of zeolitic imidazolate framework (ZIF-8) has been explored by making it multifunctional. Dual active sites were incorporated such as acid (dodecatungstophosphoric acid, DTP) and metal (Pd°) to prepare 5% Pd-DTP@ZIF-8. DTP was encapsulated inside the cage of ZIF-8 by in-situ and bottle around the ship approach whereas Pd was loaded ex-situ by simple wet impregnation method. The catalytic efficiency was tested for one pot synthesis of 3-phenyl propyl benzoate (3-PPB), a perfumery compound, from cinnamyl alcohol and benzoic anhydride. Trans-esterification of cinnamyl alcohol with benzoic anhydride gives cinnamyl benzoate which on further hydrogenation gives 3-PPB. Three different supports were screened such as ZIF-8, K10 and MCF out of which ZIF-8 showed the maximum activity because of its high surface area and smaller pore diameter. Further Pd, Ni and Cu metals were studied for selective hydrogenation of C[dbnd]C bond among which 5% Pd-DTP@ZIF-8 gave almost 98% conversion of cinnamyl benzoate to 3-PPB with 93% selectivity. Fresh and spent catalysts were characterized by various techniques. 5% Pd-DTP@ZIF-8 showed anti-leaching property with great thermal stability. The turn over frequency and turn over number of the catalyst was observed to be 0.058 s?1 and 835, respectively. A kinetic model was developed with good fit using LHHW mechanism and the activation energy calculated as 17.45 kcal/mol for hydrogenation step. Thus, the reaction was found to be kinetically controlled. The entire process is green.
- Malkar, Radhika S.,Yadav, Ganapati D.
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- Photochemical Activation of Aromatic Aldehydes: Synthesis of Amides, Hydroxamic Acids and Esters
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A cheap, facile and metal-free photochemical protocol for the activation of aromatic aldehydes has been developed. Utilizing thioxanthen-9-one as the photocatalyst and cheap household lamps as the light source, a variety of aromatic aldehydes have been activated and subsequently converted in a one-pot reaction into amides, hydroxamic acids and esters in good to high yields. The applicability of this method was highlighted in the synthesis of Moclobemide, a drug against depression and social anxiety. Extended and detailed mechanistic studies have been conducted, in order to determine a plausible mechanism for the reaction.
- Nikitas, Nikolaos F.,Apostolopoulou, Mary K.,Skolia, Elpida,Tsoukaki, Anna,Kokotos, Christoforos G.
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supporting information
p. 7915 - 7922
(2021/05/03)
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- Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
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The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
- Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
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supporting information
p. 16470 - 16485
(2021/10/20)
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- Hydrogen-bond-assisted transition-metal-free catalytic transformation of amides to esters
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The amide C-N cleavage has drawn a broad interest in synthetic chemistry, biological process and pharmaceutical industry. Transition-metal, luxury ligand or excess base were always vital to the transformation. Here, we developed a transition-metal-free hydrogen-bond-assisted esterification of amides with only catalytic amount of base. The proposed crucial role of hydrogen bonding for assisting esterification was supported by control experiments, density functional theory (DFT) calculations and kinetic studies. Besides broad substrate scopes and excellent functional groups tolerance, this base-catalyzed protocol complements the conventional transition-metal-catalyzed esterification of amides and provides a new pathway to catalytic cleavage of amide C-N bonds for organic synthesis and pharmaceutical industry. [Figure not available: see fulltext.]
- Huang, Changyu,Li, Jinpeng,Wang, Jiaquan,Zheng, Qingshu,Li, Zhenhua,Tu, Tao
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- Sustainable Palladium-Catalyzed Tsuji-Trost Reactions Enabled by Aqueous Micellar Catalysis
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Palladium-catalyzed allylic substitution, or "Tsuji-Trost"reactions, can be run under micellar catalysis conditions featuring not only chemistry in water but also numerous combinations of reaction partners that require low levels of palladium, typically on the order of 1000 ppm (0.1 mol %). These couplings are further characterized by especially mild conditions, leading to a number of cases not previously reported in an aqueous micellar medium. Inclusion of diverse nucleophiles, such as N-H heterocycles, alcohols, dicarbonyl compounds, and sulfonamides is described. Intramolecular cyclizations further illustrate the broad utility of this process. In addition to recycling studies, a multigram scale example is reported, indicative of the prospects for scale up.
- Braga, Felipe C.,Gallou, Fabrice,Lee, Nicholas R.,Lippincott, Daniel J.,Lipshutz, Bruce H.,Moghadam, Farbod A.,Zhu, Bingchun
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supporting information
(2020/07/15)
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- Catalytic conversion of ketones to esters: Via C(O)-C bond cleavage under transition-metal free conditions
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The catalytic conversion of ketones to esters via C(O)-C bond cleavage under transition-metal free conditions is reported. This catalytic process proceeds under solvent-free conditions and offers an easy operational procedure, broad substrate scope with excellent selectivity, and reaction scalability. This journal is
- Subaramanian, Murugan,Ramar, Palmurukan M.,Rana, Jagannath,Gupta, Virendra Kumar,Balaraman, Ekambaram
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supporting information
p. 8143 - 8146
(2020/09/09)
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- Asymmetric Synthesis of α-Quaternary γ-Lactams through Palladium-Catalyzed Asymmetric Allylic Alkylation
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The synthesis of chiral unsaturated γ-lactams is reported featuring a highly enantioselective palladium-catalyzed asymmetric allylic alkylation of α, γ-disubstituted 2-silyloxypyrroles. This method allows a straightforward access to optically active γ-lactams bearing an α-quaternary stereogenic center in high yields (up to 93%), high regioselectivities (up to >20:1), and excellent enantioselectivities (up to 95% ee). To further demonstrate the synthetic utility of the method, the resulting allylated products were converted to various versatile chiral building blocks, such as pyrrolidines and pyrrolidinones.
- Song, Tao,Arseniyadis, Stellios,Cossy, Janine
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supporting information
p. 603 - 607
(2019/02/28)
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- Dibromination of alkenes with LiBr and H2O2 under mild conditions
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Electron-rich and electron-poor alkenes, and alkenes bearing protecting groups can be efficiently and stereoselectively converted to trans-dibromides using LiBr/H2O2 and AcOH as a proton source in 1,4-dioxane. For most substrates addition of 0.1 mol% of PhTeTePh enhances the reaction rate and the yield of the products. Experimental data suggest that the brominating agent prepared in situ is molecular bromine and that LiBr assists the activation of H2O2 allowing bromination to occur using AcOH as a mild proton source in uncatalyzed experiments. Scale-up is feasible: 10.0 mmol of 1-octene was quantitatively converted to 1,2-dibromooctene in one hour of reaction at room temperature.
- Martins, Nayara Silva,Alberto, Eduardo E.
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supporting information
p. 161 - 167
(2017/12/28)
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- Oxidation-Reduction Condensation of Diazaphosphites for Carbon-Heteroatom Bond Formation Based on Mitsunobu Mechanism
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An efficient oxidation-reduction condensation reaction of diazaphosphites with various nonacidic pronucleophiles in the presence of DIAD as a weak oxidant has been developed for carbon-heteroatom bond formation. This mild process affords structurally diverse tertiary amines, secondary amines, esters, ethers, and thioethers in moderate to excellent yields. The selective synthesis of secondary amines from primary amines has been achieved. Importantly, a practical application to the synthesis of antiparkinsonian agent piribedil has been demonstrated.
- Huang, Hai,Kang, Jun Yong
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p. 544 - 547
(2017/02/10)
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- Copper-catalyzed regioselective allylic oxidation of olefins via C–H activation
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A regioselective oxidation of allylic C–H bond to C–O bond catalyzed by copper (I) was developed with diacyl peroxides as oxidants. The oxidation of allylic C–H bond was accomplished with good yield and regioselectivity under mild reaction conditions. This method has a broad substrate scope including cyclic olefins, terminal and internal acyclic olefins and allyl benzene compounds. The reaction proceeds by a radical mechanism as suggested by spin trapping experiments.
- Zhu, Nengbo,Qian, Bo,Xiong, Haigen,Bao, Hongli
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supporting information
p. 4125 - 4128
(2017/09/29)
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- Iron-catalyzed esterification of allylic sp3 C–H bonds with carboxylic acids: Facile access to allylic esters
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The first general and efficient iron-catalyzed esterification of allylic sp3 C–H bonds with carboxylic acids using ionic iron(III) complexes (1–4) as a catalyst and DTBP (DTBP?=?di-tert-butyl peroxide) as an oxidant is achieved. A variety of allylic esters were synthesized in good to excellent yields using the ionic iron(III) complex 2 as a catalyst in a 5?mol% loading. This reaction is characterized by its high efficiency, broad substrate scope with excellent steric hindrance tolerance and good functional group compatibility.
- Lu, Bing,Zhu, Fan,Wang, Dan,Sun, Hongmei,Shen, Qi
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supporting information
p. 2490 - 2494
(2017/05/31)
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- A pH-controlled recyclable indolinooxazolidine tagged N-heterocyclic carbene Ru catalyst for olefin metathesis
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An indolinooxazolidine tagged N-heterocyclic carbene Ru olefin metathesis catalyst was synthesized and the molecular structure of this new Ru complex was determined by single crystal X-ray diffraction. This complex is a homogeneous catalyst and can be recovered by controlling the polarity of the indolinooxazolidine tag. Under acidic conditions the indolinooxazolidine tag exists as an open protonated form and under basic conditions the tag is in a closed form. The distribution of this catalyst in a two-phase system can be controlled by simply changing the pH, making the recovery of this catalyst easily obtainable.
- Duan, Yulian,Wang, Tao,Xie, Qingxiao,Yu, Xiaobo,Guo, Weijie,Wu, Shutao,Li, Danfeng,Wang, Jianhui,Liu, Guiyan
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supporting information
p. 5986 - 5993
(2017/07/11)
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- Ruthenium-Catalyzed Cross-Metathesis of Allyl Acetate and Styrenes: A Practical Approach to the Synthesis of Tripolinolate A and Its Analogs
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The scope of the Ru-catalyzed cross-metathesis of allyl acetates and styrenes was explored. A variety of electronically and structurally divergent styrenes were tolerated, and the resultant products were obtained in reasonable yields. The reported method was utilized in the synthesis of inhibitors of the proliferation of glioma and colorectal cancer cells, tripolinolate A and its diacetate analog.
- Araki, Yasuhiro,Topolov?an, Nikola,Kotora, Martin
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supporting information
p. 1736 - 1739
(2017/04/13)
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- Sol–Gel Immobilized N-Heterocyclic Carbene Gold Complex as a Recyclable Catalyst for the Rearrangement of Allylic Esters and the Cycloisomerization of γ-Alkynoic Acids
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The synthesis of a bis-silylated (NHC)AuCl (NHC=N-heterocyclic carbene) complex and the formation of a hybrid silica material by the sol–gel process by cogelification with tetraethylorthosilicate under fluoride catalysis are described. This material was characterized by using 29Si solid-state NMR spectroscopy, N2 sorption measurements, electron microscopy, and elemental analysis. It was tested as a reusable catalyst in the rearrangement of allylic esters in conjunction with a silver salt under microwave conditions and it displayed a much better performance than a homogeneous analogue. This catalyst is active and recyclable in the cycloisomerization of γ-alkynoic acids to five-membered enol-lactones at room temperature in two reaction media, a toluene/water biphasic system and a deep eutectic solvent.
- Ferré, Meritxell,Catto?n, Xavier,Wong Chi Man, Michel,Pleixats, Roser
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p. 2824 - 2831
(2016/09/13)
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- Copper-catalyzed cross-coupling of thiols, alcohols, and oxygen for the synthesis of esters
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Copper-catalyzed, one-pot, three-component coupling reactions using thiols, alcohols, and oxygen to form a variety of esters in good yields were studied. In the presence of easily oxidized benzylic and allylic alcohols, thiols were selectively oxidized to form thionoesters, which underwent facile S/O exchange to afford esters. Thiols may be used as an alternative benzoyl source under mild aerobic conditions.
- Lim, Seungyeon,Ji, Miran,Wang, Xi,Lee, Chan,Jang, Hye-Young
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supporting information
p. 591 - 595
(2015/01/30)
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- Bis azide-triphenylphosphine as a reagent for esterification at room temperature
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Modified Staudinger reaction is a well-established reaction for the amide synthesis from organic azides and carboxylic acids in the presence of phosphorous reagents. In contrary to this, it is notable that bis azide in the presence of triethylphosphite or trimethylphosphite does not afford the expected bis amides but affords the ethyl or methyl esters of the carboxylic acids respectively. This serendipitous observation when further investigated results in the discovery of bis azide-triphenylphosphine as an efficient reagent for esterification at room temperature.
- Dinesh, Murugan,Archana, Sivasubramaniyan,Ranganathan, Raja,Sathishkumar, Murugan,Ponnuswamy, Alagusundaram
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supporting information
p. 6975 - 6979
(2015/11/27)
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- Method for Esterification of Alcohols
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(A) ionic liquid and organic base to form the catalyst carbene by mixing the step ; (b) said carbene catalysts based on supplyingcarbon dioxide to the by forming adducts the reacting ; (c) said adducts by reacting allyl alcohol to form intermediates ; (d) said of intermediates of and fragmentation to provide by the process of forming a and formic aldehyde compounds; and (e) said aldehyde compounds and said allyl alcohol an oxidation reduction esterification to obtain an ester product through the esterification of alcohol including provides method. (by machine translation)
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Paragraph 0059; 0060; 0062; 0063
(2016/10/07)
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- Versatile and sustainable alcoholysis of amides by a reusable CeO 2 catalyst
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CeO2 catalyzed the esterification between an equivalent molar ratio of primary amides and alcohols under neutral conditions, which provides the first versatile reusable catalytic system for direct alcoholysis of amides to esters with wider scope and 67 times higher turnover number (TON) than previous catalytic systems.
- Siddiki, S. M. A. Hakim,Touchy, Abeda Sultana,Tamura, Masazumi,Shimizu, Ken-Ichi
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p. 35803 - 35807
(2014/11/07)
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- A chiral sulfoxide-ligated ruthenium complex for asymmetric catalysis: Enantio- and regioselective allylic substitution
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The design and synthesis of a novel chiral sulfoxide-ligated cyclopentadienyl ruthenium complex is described. Its utility as an asymmetric variant of [CpRu(MeCN)3]PF6 is demonstrated through its ability to function in the branched-selective asymmetric allylic alkylation of phenols and carboxylic acids. Water has also been shown to act as a competent nucleophile in this reaction to generate branched allyl alcohols with good regio- and enantioselectivities.
- Trost, Barry M.,Rao, Meera,Dieskau, Andre P.
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p. 18697 - 18704
(2014/01/06)
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- Copper-catalyzed benzylic oxidation of C(sp3)-H bonds
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A selective oxidation of benzylic C(sp3)-H bonds to C(sp 3)-O bonds catalyzed by copper complexes of quinoline-imine ligands was developed with peresters as oxidants under mild reaction conditions, which converted benzylic methylenes directly into benzylic alcohols and esters by means of direct C-H bond functionalization.
- Zhang, Bo,Zhu, Shou-Fei,Zhou, Qi-Lin
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supporting information
p. 2033 - 2037
(2013/03/13)
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- Enantioselective functionalization of allylic C-H bonds following a strategy of functionalization and diversification
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We report the enantioselective functionalization of allylic C-H bonds in terminal alkenes by a strategy involving the installation of a temporary functional group at the terminal carbon atom by C-H bond functionalization, followed by the catalytic diversification of this intermediate with a broad scope of reagents. The method consists of a one-pot sequence of palladium-catalyzed allylic C-H bond oxidation under neutral conditions to form linear allyl benzoates, followed by iridium-catalyzed allylic substitution. This overall transformation forms a variety of chiral products containing a new C-N, C-O, C-S, or C-C bond at the allylic position in good yield with a high branched-to-linear selectivity and excellent enantioselectivity (ee ≤97%). The broad scope of the overall process results from separating the oxidation and functionalization steps; by doing so, the scope of nucleophile encompasses those sensitive to direct oxidative functionalization. The high enantioselectivity of the overall process is achieved by developing an allylic oxidation that occurs without acid to form the linear isomer with high selectivity. These allylic functionalization processes are amenable to an iterative sequence leading to (1,n)-functionalized products with catalyst-controlled diastereo- and enantioselectivity. The utility of the method in the synthesis of biologically active molecules has been demonstrated.
- Sharma, Ankit,Hartwig, John F.
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supporting information
p. 17983 - 17989
(2014/01/06)
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- N-heterocyclic carbene catalysed oxidative coupling of aldehydes with alcohols/thiols and one-pot oxidation/esterification of allylic alcohols
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A versatile carbene-catalysed oxidation protocol involving N-heterocyclic carbene catalysts and 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) is described for the synthesis of esters, cinnamic acids, and thioesters. A wide range of esters, thioesters, and cinnamic acids were obtained by metal-free coupling of aldehydes with aliphatic, allylic and aromatic alcohols, benzyl mercaptan, and water. In addition to the oxidative coupling of aldehydes with nucleophiles, dehydrogenation of saturated aldehydes and oxidation of allylic alcohols were found under our oxidative coupling conditions. Unlike other TEMPO-mediated oxidative esterification reactions, this reaction does not proceed through a TEMPO ester intermediate to form esters and thioesters. N-Heterocyclic carbene complexes catalyse various oxidative coupling reactions in the presence of TEMPO. A variety of α,β-unsaturated and saturated esters, and aromatic esters and thioesters were synthesised. Copyright
- Ji, Miran,Wang, Xi,Lim, Yu Na,Kang, Ye-Won,Jang, Hye-Young
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supporting information
p. 7881 - 7885
(2014/01/06)
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- CeO2 as a versatile and reusable catalyst for transesterification of esters with alcohols under solvent-free conditions
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CeO2 acted as an efficient and reusable heterogeneous catalyst for transesterification of esters with alcohols under the solvent-free conditions at 160 °C. Among the 11 kinds of metal oxides, CeO2 is the most suitable catalyst in terms of catalytic activity, leaching-resistance and reusability. This catalytic system tolerates various esters and alcohols, and valuable esters such as heteroaromatic esters and benzyl benzoates are produced, demonstrating a practical utility of the system. On the basis of kinetic analysis and in situ IR studies of adsorbed species, a reaction mechanism is proposed, in which proton abstraction of alcohol by a Lewis base site of CeO2 to yield alkoxide species is the rate-limiting step.
- Tamura, Masazumi,Hakim Siddiki,Shimizu, Ken-Ichi
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p. 1641 - 1646
(2013/09/24)
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- Direct esterification of carboxylic acids with alcohols catalyzed by Iron(III) acetylacetonate complex
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Direct condensation of carboxylic acids and alcohols with electronic, steric, and functional group variations was carried out using the environmentally benign, moisture-stable, inexpensive, and recoverable iron(III) acetylacetonate [Fe(acac)3] as catalyst (5 mol%). This iron salt efficiently catalyzed the esterification of several primary and secondary alcohols in refluxing xylene, without the need for a dehydration reagent. The chemoselectivity of the proposed protocol was demonstrated by the selective esterification of primary alcohol functionality in racemic 1-phenylethane-1,2- diol with benzoic acid. The esterification was also applicable to unmasked α-hydroxyacid, guasiaromatic, heterocyclic, and N-protected amino acids. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.
- Weng, Shiue-Shien,Chen, Fong-Kuang,Ke, Chih-Shueh
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p. 2615 - 2621
(2013/07/26)
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- Organocatalytic selective benzoylation of alcohols with trichloromethyl phenyl ketone: Inverse selectivity in benzoylation of alcohols containing phenol or aromatic amine functionality
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Trichloromethyl phenyl ketone benzoylates primary and secondary aliphatic alcoholic groups in compounds also containing a phenolic group in the presence of 2-10 mol % of PMDETA organocatalyst at room temperature in high yields and excellent selectivity. It also shows the potential to selectively benzoylate primary alcoholic groups of aminoarylalkanols and primary-secondary diols as well as primary amino group of alkyl amines in the presence of aryl amines under similar conditions. A rationale for the selectivity and efficiency of the reaction has been provided.
- Ram, Ram N.,Soni, Vineet Kumar,Gupta, Dharmendra Kumar
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p. 9068 - 9075
(2012/11/07)
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- Solvent-free transesterification in a ball-mill over alumina surface
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An efficient procedure for transesterification has been developed in a ball-mill in the absence of any solvent, acid/base or metal catalyst. A variety of methyl, ethyl, allyl esters have been transesterified to higher benzyl and other esters in high yields by this procedure.
- Chatterjee, Tanmay,Saha, Debasree,Ranu, Brindaban C.
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experimental part
p. 4142 - 4144
(2012/08/28)
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- Transesterification catalyzed by iron(III) β-diketonate species
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A practical and clean protocol for transesterification catalyzed by a 5 mol % cheap, non-toxic and moisture stable Fe(acac)3 or other iron(III) β-diketonate species in solvent, such as heptane under azeotropic condition is developed. A remarkable rate enhancement was observed upon the addition of 5 mol % of an inorganic base, such as Na2CO3, which suggests that faster formation of a dimeric μ-alkoxy-bridged iron(III) species under alkaline conditions facilitates catalytic turnover. This system provides smooth transesterification over a wide range of structurally diverse esters and alcohols without disturbing functional groups. In addition, the use of iron β-diketonate complexes as catalysts is more environmentally friendly, safer, and economical than other transition-metal catalysts. Preliminary mechanistic studies indicate that the active catalyst is likely a dimeric μ-alkoxy-bridged iron(III) species, as determined by X-ray crystallography of [Fe(dbm)2(O-n-Bu)]2 derived from the alcoholysis of Fe(dbm)3 under alkaline conditions.
- Weng, Shiue-Shien,Ke, Chih-Shueh,Chen, Fong-Kuang,Lyu, You-Fu,Lin, Guan-Ying
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supporting information; experimental part
p. 1640 - 1648
(2011/04/17)
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- N-heterocyclic carbene-mediated oxidative esterification of aldehydes: Ester formation and mechanistic studies
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An unexpected N-heterocyclic carbene-catalyzed esterification of α,β-unsaturated aldehydes including aromatic aldehydes with reactive cinnamyl bromides in the presence of air oxygen or MnO2 as an oxidant is described. In the presence of oxygen, halogenated and electron-deficient aldehydes react smoothly to furnish esters in good yields. Great efforts have been made on mechanistic studies to deduce a plausible mechanism, based on the experimental results and isotopic labeling experiment.
- Maji, Biswajit,Vedachalan, Seenuvasan,Ge, Xin,Cai, Shuting,Liu, Xue-Wei
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scheme or table
p. 3016 - 3023
(2011/06/20)
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- Pd(OAc)2/dppf as an efficient and highly active catalyst for the allylation of amines, alcohols and carboxylic acids with 1-phenyl-1-propyne
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Pd(OAc)2/1,1′-bis(diphenylphosphino)ferrocene as an efficient, highly active catalyst for the allylation of amines, alcohols and carboxylic acids with 1-phenyl-1-propyne has been developed. The effect of various reaction parameters, such as ligand, time, solvent, temperature, metal: ligand ratio and catalyst concentration on yields of the product were investigated. The optimized procedure works well under mild operating conditions and permits rapid generation of a library for various allylated products.
- Wagh, Yogesh S.,Sawant, Dinesh N.,Tambade, Pawan J.,Dhake, Kishor P.,Bhanage, Bhalchandra M.
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experimental part
p. 2414 - 2421
(2011/04/26)
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- Allylation of 1-phenyl-1-propyne with N- and O-pronucleophiles using polymer supported triphenylphosphine palladium complex as a heterogeneous and recyclable catalyst
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Simple methodology for the allylation of various N- and O-pronucleophiles with 1-phenyl-1-propyne as an allylating agent, using PS-TPP-Pd (polymer supported triphenylphosphine palladium) as a highly active heterogeneous recyclable catalyst has been developed. The protocol is applicable for a wide variety of hindered and functionalized aromatic amines, alcohols, and carboxylic acids. The catalyst exhibited remarkable catalytic activity for five consecutive recycles.
- Wagh, Yogesh S.,Sawant, Dinesh N.,Dhake, Kishor P.,Deshmukh, Krishna M.,Bhanage, Bhalchandra M.
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experimental part
p. 5676 - 5679
(2011/11/06)
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- Iridium-catalyzed kinetic asymmetric transformations of racemic allylic benzoates
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Versatile methods for iridium-catalyzed, kinetic asymmetric substitution of racemic, branched allylic esters are reported. These reactions occur with a variety of aliphatic, aryl, and heteroaryl allylic benzoates to form the corresponding allylic substitution products in high yields (74-96%) with good to excellent enantioselectivity (84-98% ee) with a scope that encompasses a range of anionic carbon and heteroatom nucleophiles. These kinetic asymmetric processes occur with distinct stereochemical courses for racemic aliphatic and aromatic allylic benzoates, and the high reactivity of branched allylic benzoates enables enantioselective allylic substitutions that are slow or poorly selective with linear allylic electrophiles.
- Stanley, Levi M.,Bai, Chen,Ueda, Mitsuhiro,Hartwig, John F.
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supporting information; experimental part
p. 8918 - 8920
(2010/08/21)
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- A fast and simple method for the acylation of alcohols with acid chlorides promoted by metallic samarium
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Acylation of primary, secondary, allyl and benzyl alcohols with acid chlorides promoted by samarium metal under neutral condition gave carboxylic acid esters in good to excellent yields. Acylation of a tertiary alcohol did not occur under the same reaction conditions.
- Jia, Xue-Shun,Wang, Hai-Long,Huang, Qing,Kong, Ling-Long,Zhang, Wei-He
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p. 135 - 138
(2007/10/03)
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- Fluoroalkyldistannoxane Catalysts for Transesterification in Fluorous Biphase Technology
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Novel, practical protocols of transesterification have been advanced with recourse to fluorous biphase technology. The fluoroalkyldistannoxane catalysts enable transesterification in FC-72 solvent to furnish 100% yields of the desired esters by use of reactants ester and alcohol in a 1:1 ratio. The catalysts also work in FC-72/organic solvent system as well as in toluene alone. A number of esters and alcohols bearing various functional groups are employable. The catalysts can be totally recovered and reused. More conveniently, the catalyst solution in FC-72 which is separated from the reaction mixture is directly used for the next reaction.
- Xiang, Jiannan,Orita, Akihiro,Otera, Junzo
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- A practical and green chemical process: Fluoroalkyldistannoxane-catalyzed biphasic transesterification
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There is no need for the recovery of the catalyst in the fluorous biphasic transesterification catalyzed by [{Cl(C6F13CH2CH2)2 SnOSn(C6F13CH2CH2) 2Cl}2] (1; see scheme), which results in quantitative conversions and yields. An FC-72 solution of the dimeric flouroalkyldistannoxane 1 can be recycled repeatedly without having to recover the neat catalyst.
- Xiang, Jiannan,Toyoshima, Shinji,Orita, Akihiro,Otera, Junzo
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p. 3670 - 3672
(2007/10/03)
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- Cu(OTf)2-DBN/DBU complex as an efficient catalyst for allylic oxidation of olefins with tert-butyl perbenzoate
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Olefins, on treatment with tert-butyl perbenzoate in the presence of a catalytic amount of a complex of Cu(OTf)2 and chelating ligands such as DBN and DBU gave allylic benzoates under milder conditions. A variety of olefins were tested in the reaction.
- Sekar, Govindasamy,DattaGupta, Arpita,Singh, Vinod K.
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p. 8435 - 8436
(2007/10/03)
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