- The role of neutral donor ligands in the isoselective ring-opening polymerization of: Rac -β-butyrolactone
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Isoenriched poly-3-hydroxybutyrate (P3HB) is a biodegradable material with properties similar to isotactic polypropylene, yet efficient routes to this material are lacking after 50+ years of extensive efforts in catalyst design. In this contribution, a novel lanthanum aminobisphenolate catalyst (1-La) can access isoenriched P3HB through the stereospecific ring-opening polymerization (ROP) of rac-β-butyrolactone (rac-BBL). Replacing the tethered donor group of a privileged supporting ligand with a non-coordinating benzyl substituent generates a catalyst whose reactivity and selectivity can be tuned with inexpensive achiral neutral donor ligands (e.g. phosphine oxides, OPR3). The 1-La/OPR3 (R = n-octyl, Ph) systems display high activity and are the most isoselective homogeneous catalysts for the ROP of rac-BBL to date (0 °C: Pm = 0.8, TOF ~190 h-1). Combined reactivity and spectroscopic studies provide insight into the active catalyst structure and ROP mechanism. Both 1-La(TPPO)2 and a structurally related catalyst with a tethered donor group (2-Y) operate under chain-end stereocontrol; however, 2-RE favors formation of P3HB with opposite tacticity (syndioenriched) and its ROP activity and selectivity are totally unaffected by added neutral donor ligands. Our studies uncover new roles for neutral donor ligands in stereospecific ROP, including suppression of chain-scission events, and point to new opportunities for catalyst design. This journal is
- Dong, Xiang,Robinson, Jerome R.
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p. 8184 - 8195
(2020/09/07)
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- Aldehydes as potential acylating reagents for oxidative esterification by inorganic ligand-supported iron catalysis
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The oxidative esterification of various aldehydes with alcohols could be achieved by a heterogeneous iron(iii) catalyst supported on a ring-like POM inorganic ligand under mild conditions, affording the corresponding esters, including several drug molecules and natural products, in high yields. ESI-MS and control experiments demonstrated that POM-FeV(O) was the active catalytic species and the plausible mechanism was presented. More importantly, the 6th run of the iron catalyst recycles shows only a slight decrease in the yield.
- Yu, Han,Wang, Jingjing,Wu, Zhikang,Zhao, Qixin,Dan, Demin,Han, Sheng,Tang, Jiangjiang,Wei, Yongge
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supporting information
p. 4550 - 4554
(2019/08/21)
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- Chain Multiplication of Fatty Acids to Precise Telechelic Polyethylene
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Starting from common monounsaturated fatty acids, a strategy is revealed that provides ultra-long aliphatic α,ω-difunctional building blocks by a sequence of two scalable catalytic steps that virtually double the chain length of the starting materials. The central double bond of the α,ω-dicarboxylic fatty acid self-metathesis products is shifted selectively to the statistically much-disfavored α,β-position in a catalytic dynamic isomerizing crystallization approach. “Chain doubling” by a subsequent catalytic olefin metathesis step, which overcomes the low reactivity of this substrates by using waste internal olefins as recyclable co-reagents, yields ultra-long-chain α,ω-difunctional building blocks of a precise chain length, as demonstrated up to a C48 chain. The unique nature of these structures is reflected by unrivaled melting points (Tm=120 °C) of aliphatic polyesters generated from these telechelic monomers, and by their self-assembly to polyethylene-like single crystals.
- Witt, Timo,H?u?ler, Manuel,Kulpa, Stefanie,Mecking, Stefan
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supporting information
p. 7589 - 7594
(2017/06/13)
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- Synthesis of α-alkenyl-β-hydroxy adducts by α-addition of unprotected 4-bromocrotonic acid and amides with aldehydes and ketones by chromium(II)-mediated reactions
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The regioselective and diastereoselective chromium(II)-mediated reactions of 4-bromocrotonic acid or amides with aldehydes and ketones can proceed without the need to protect protic sites to generate the respective α-alkenyl-β-hydroxy adducts, i.e. formally the addition of the α-anion of a carboxylic acid or amide to an oxo-compound is featured.
- Wessjohann, Ludger A.,Wild, Harry,Ferreira, Leonildo A.,Schrekker, Henri S.
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p. 674 - 679
(2016/07/19)
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- Versatile PdTe/C catalyst for liquid-phase oxidations of 1,3-butadiene
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A commercial Pd catalyst based on Sibunit carbon support was treated with H6TeO6 in a reducing media to obtain a Te coating on the surface of Pd particles. The PdTe/C catalyst prepared in this way showed the ability to control the radical chain oxidation of 1,3-butadiene by promoting the selective formation of 2-butene-1,4-diol, 4-hydroxybut-2-enal and furan in DMA (total selectivity of 61% and yield of 7%). At the same time, the catalyst induced oxidation of 1,3-butadiene by a non-radical heterolytic mechanism involving the formation of two groups of primary products: (1) crotonaldehyde and methyl vinyl ketone and (2) the products of oxygenation at the 1,4-positions. The compounds of the second group including 1,4-dimethoxy-2-butene and maleic acid dimethyl ester were formed on PdTe centers in MeOH. Increasing the Te concentration in the PdTe/C catalyst forced the conversion of 1,3-butadiene toward 1,4-oxygenation and simultaneously decreased the intensity of secondary oxidation, resulting in the selective formation of derivatives of the 1,4-oxygenation - 1,4-dimethoxy-2-butene and allenic alcohol methyl ether (total selectivity of 84% and yield of 48%).
- Kuznetsova,Zudin,Kuznetsova,Zaikovskii,Kajitani,Utsunomiya,Takahashi
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- Ligand-controlled insertion regioselectivity accelerates copolymerisation of ethylene with methyl acrylate by cationic bisphosphine monoxide-palladium catalysts
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A new series of palladium catalysts ligated by a chelating bisphosphine monoxide bearing diarylphosphino groups (aryl-BPMO) exhibits markedly higher reactivity for ethylene/methyl acrylate copolymerisation when compared to the first generation of alkyl-BPMO-palladium catalysts that contain a dialkylphosphino moiety. Mechanistic studies suggest that the origin of this disparate catalyst behavior is a change in regioselectivity of migratory insertion of the acrylate comonomer as a function of the phosphine substituents. The best aryl-BPMO-palladium catalysts for these copolymerisations were shown to undergo exclusively 2,1-insertion, and this high regioselectivity avoids formation of a poorly reactive palladacycle intermediate. Furthermore, the aryl-BPMO-palladium catalysts can copolymerise ethylene with other industrially important polar monomers.
- Mitsushige, Yusuke,Carrow, Brad P.,Ito, Shingo,Nozaki, Kyoko
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p. 737 - 744
(2015/12/26)
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- Liberation of methyl acrylate from metallalactone complexes via M-O ring opening (M = Ni, Pd) with methylation agents
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Ring opening of various nickela- and palladalactones induced by the cleavage of the M-O bond by methyl trifluoromethanesulfonate (MeOTf) and methyl iodide (MeI) is examined. Experimental evidence supports the mechanism of ring opening by the alkylating agent followed by β-H elimination leading to methyl acrylate and a metal-hydride species. MeOTf shows by far higher efficiency in the lactone ring opening than any other methylating agent including the previously reported methyl iodide.
- Lee, S. Y. Tina,Ghani, Amylia Abdul,D'Elia, Valerio,Cokoja, Mirza,Herrmann, Wolfgang A.,Basset, Jean-Marie,Kuehn, Fritz E.
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supporting information
p. 3512 - 3517
(2013/11/06)
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- Multimetallic Ir-Sn3-catalyzed substitution reaction of π-activated alcohols with carbon and heteroatom nucleophiles
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An atom economic and catalytic substitution reaction of π-activated alcohols by a multimetallic IreSn3 complex has been demonstrated. The multimetallic IreSn3 complex can be easily synthesized from the reaction between [Cp*IrCl2]2 and SnCl2. In presence of as little as 1 mol % of the catalyst three different types of π-activated alcohols, namely benzyl, allyl, and propargyl alcohols, have been successfully transformed into alkylated products using carbon (arenes, heteroarenes, allyltrimethylsilane, and 1,3-dicarbonyls), nitrogen (sulfonamides), oxygen (alcohols), and sulfur (thiols) nucleophiles in very high yields. An electrophilic mechanism is proposed from the Hammett correlation study.
- Maity, Arnab Kumar,Chatterjee, Paresh Nath,Roy, Sujit
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p. 942 - 956
(2013/07/25)
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- Manganese phthalocyanine immobilized on silica gel: Efficient and recyclable catalyst for single-step oxidative esterification of aldehydes with alcohols
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The functionalization of silica gel was carried out using 3-aminopropyltriethoxysilane as a reactive surface modifier followed by covalent grafting of novel tetrakis-(2-methoxy-4-formylphenoxy)phthalocyaninato manganese(III) acetate complex. The resulting inorganic-organic hybrid material was found to be a highly selective and recyclable catalyst for the single-step synthesis of esters. The catalyst was characterized by elemental analysis (CHN), diffuse reflectance UV-visible, 13C CPMAS and 29Si CPMAS NMR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area analysis, energy dispersive X-ray fluorescence (ED-XRF), Fourier-transform infrared (FT-IR) and atomic absorption spectroscopy (AAS) techniques, which demonstrates the covalent grafting of the complex onto functionalized silica gel. The catalytic performance of the novel inorganic-organic hybrid catalyst was evaluated in the direct oxidative esterification of aldehydes with alcohols, at ambient temperature, using hydrogen peroxide as an environment friendly oxidant. The hybrid catalyst presented up to 100% of substrate conversion with high turn-over numbers (TONs), up to 100% of selectivity toward the ester product, and can be recovered and reused for multiple cycles without appreciable loss in its catalytic activity.
- Sharma,Gulati, Shikha
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p. 291 - 303
(2012/10/30)
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- Practical, catalytic enantioselective hydrogenation to synthesize N -unprotected β-amino esters
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Practical and simple catalytic enantioselective hydrogenation reactions to synthesize N-unprotected β-amino esters have been developed: (1) asymmetric hydrogenation of N-unprotected β-enamine ester and (2) asymmetric direct reductive amination of β-keto esters using ammonium salts. A Ru-DM-SEGPHOS complex was used as the catalyst in both cases and gave high enantioselectivity, high reactivity, and wide substrate applicability. These protocols greatly reduced reaction time and waste compared to conventional synthetic routes. The direct reductive amination route was demonstrated on a >100 kg scale.
- Matsumura, Kazuhiko,Zhang, Xiaoyong,Hori, Kiyoto,Murayama, Toshiyuki,Ohmiya, Tadamasa,Shimizu, Hideo,Saito, Takao,Sayo, Noboru
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p. 1130 - 1137
(2012/01/03)
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- Gold supported on nanocrystalline β-Ga2O3 as a versatile bifunctional catalyst for facile oxidative transformation of alcohols, aldehydes, and acetals into esters
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Facile oxidative transformation of alcohols, aldehydes, and acetal into esters has been demonstrated using bifunctional catalyst of gold supported nanocrystalline β-Ga2O3. The study used alcoholic gel-precipitation method to prepare nanocrystalline support and X-ray diffraction (XRD) to characterize the diffraction features of synthesized nanocrystalline support. The study observed that the Au/β-Ga 2O3 catalyst can be reused after aerobic oxidation with maintaining catalytic activity and selectivity for oxidative esterification. The study also observed that aromatic and aliphatic primary alcohols can be converted into their methyl, ethyl, or propyl esters with high selectivities. The study also found that the esters produced after esterification were in good yields.
- Su, Fang-Zheng,Ni, Ji,Sun, Hao,Cao, Yong,He, Yong,Fan, Kang-Nian
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supporting information; experimental part
p. 7131 - 7135
(2009/08/07)
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- An efficient and regiospecific biocatalytic esterification of some organic acids using beef pancreas lipase (Bpl)
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Treatment of some aromatic and three dicarboxylic acids with methanol in the presence of beef pancreas lipase (Bpl) results in excellent yields of corresponding esters. The esterification is regiospecific to aromatic ring connected carboxylic functionalities.
- Roy,Sarkar,Paul
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p. 1767 - 1769
(2007/10/03)
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- N,N′-Diiodo-N,N′-1,2-ethanediylbis(p-toluenesulfonamide) as a reagent for conversion of aldehydes to methyl esters
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N,N′-Diiodo-N,N′-1,2-ethanediylbis(p-toluenesulfonamide) (NIBTS) can be used for the oxidation of aldehydes to the corresponding methyl esters with high efficiency in a single step.
- Ghorbani-Vaghei, Ramin,Shahbazee, Elham,Veisi, Hojat
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p. 207 - 208
(2007/10/03)
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- Preparation of methyl methacrylate by carbomethoxylation of the methylacetylene-allene fraction in the presence of a palladium catalyst
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A palladium-phosphine catalytic system modified with nitrogen-containing ligands was examined. The system allows the carbomethoxylation of the methylacetylene-allene fraction yielding methyl methacrylate.
- Makarova,Korneeva,Slivinskii
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p. 190 - 192
(2007/10/03)
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- Kinetics of the Reactions of Crotonoyl Chloride with Phenols
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Unlike bimolecular reaction with alcohols, reactions of crotonoyl chloride with equimolar amounts of phenols in toluene follow the third-order kinetics and are of the second order with respect to the phenol.The effect of substituents in the phenyl ring does not obey the Hammett equation.In competitive reaction of crotonoyl chloride with equimolar amounts of phenol and an alcohol, the reaction with less acidic alcohol prevails.
- Baranovskaya, O. E.,Makitra, R. G.
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p. 1071 - 1074
(2007/10/03)
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- Reactions of β-Lactones with Potassium Alkoxides and Their Complexes with 18-Crown-6 in Aprotic Solvents
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The mechanism of the reaction of β-lactones (2-oxetanones) with potassium alkoxides in aprotic solvents was investigated.Despite previous suggestions, the attack of alkoxide ion occurs on the carbonyl carbon atom of β-lactones, cleaving the acyl-oxygen bond to yield the corresponding potassium alcoholate of the respective β-hydroxycarboxylic acid ester.Next, the unsaturated ester is formed due to potassium hydroxide elimination.The nature of the alkoxide used and complexation of alkali metal cation by crown ether have no significant effect on the reaction course in aprotic solvents.
- Kurcok, Piotr,Jedlinski, Zbigniew,Kowalczuk, Marek
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p. 4219 - 4220
(2007/10/02)
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- Anchimeric Assistance of the CO2CH3 Substituent in the Elimination Kinetics of 3-(Methoxycarbonyl)propyl Methanesulfonate in the Gas Phase
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The elimination kinetics of 3-(methoxycarbonyl)propyl methanesulfonate have been determined in a static system over the temperature range of 289.3-329.8 deg C and pressure range of 43-111 torr.The reaction, in vessels seasoned with allyl bromide and in the presence of at least an equal amount of the free radical suppressor toluene, is homogeneous, unimolecular and first-order kinetically.The rate coefficients follow the Arrhenius equation: log k1 = (13.50 +/- 0.47) - (182.2 +/- 5.3) (2.303 RT)-1.A very high extent of lactone formation suggests an unequivocal participation of the carbonyl oxygen of the CO2CH3 group.The partial rates for the parallel elimination towards the formation of butyrolactone and a small amount of methylbut-3-enoate have been estimated, reported, and discussed.The present results provide further evidence of intimate ion pair mechanisms in the gas phase pyrolyses of special types of organic molecules.
- Chuchani, Gabriel,Dominguez, Rosa M.
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p. 1295 - 1298
(2007/10/02)
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- A facile conversion of halides, alcohols and olefins to esters using iron(III) perchlorate
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A facile method has been developed for the esterification of halides/alcohols/olefins with carboxylic acids using iron(III) perchlorate.
- Kumar,Kumar,Parmar
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p. 1087 - 1094
(2007/10/02)
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- CARBONYLATION OF 1,4-DI(CHLOROMETHYL)BENZENE AND ALLYL CHLORIDE IN METHANOL, CATALYZED BY DICOBALT OCTACARBONYL
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The effects of inorganic base on the yield and selectivity of carbonylation of 1,4-di(chloromethyl)benzene and allyl chloride, catalyzed by dicobalt octacarbonyl, in methanol with carbon monoxide at atmospheric pressure have been examined.The highest yields of products were obtained with K2CO3 and Na2CO3.Addition of MeI results in a considerable increase in yields in the presence of calcium bases, givimg dimethyl 1,4-phenylenediacetate, which in the absence of MeI is formed in appreciable amounts only in the presence of sodium carbonate.
- Terekhova, M. I.,Kron, T. E.,Petrova, N. E.,Petrov, E. S.
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p. 2101 - 2104
(2007/10/02)
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- Destabilized Carbenium Ions: α-Carbomethoxy-α,α-dimethyl-methyl Cations
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Tertiary α-carbomethoxy-α,α-dimethyl-methyl cations a have been generated by electron impact induced fragmentation from the appropriately α-substituted methyl isobutyrates 1-4.The destabilized carbenium ions a can be distinguished from their more stable isomers protonated methyl methacrylate c and protonated methyl crotonate d by MIKE and CA spectra.The loss of I. and Br. from the molecular ions of 1 and 2, respectively, predominantly gives rise to the destabilized ions a, whereas loss of Cl. from +. results in a mixture of ions a and c.The loss of CH3. from +. favours skeletal rearrangement leading to ions d.The characteristic reactions of the destabilized ions a are the loss of CO and elimination of methanol.The loss of CO is associated by a very large KER and non-statistical kinetic energy release (T50 = 920 meV).Specific deuterium labelling experiments indicate that the α-carbomethoxy-α,α-dimethyl-methyl cations a rearrange via a 1,4-H shift into the carbonyl protonated methyl methacrylate c and eventually into the alkyl-O protonated methyl methacrylate before the loss of methanol.The hydrogen rearrangements exhibit a deuterium isotope effect indicating substantial energy barriers between the + isomers.Thus the destabilized carbenium ion a exists as a kinetically stable species within a potential energy well.
- Wolf, Rainer,Gruetzmacher, Hans-Fr.
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p. 398 - 404
(2007/10/02)
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- Maximally Inhibited Pyrolysis Kinetcs of Bromo Esters in the Gas Phase. The Ion Pair Mechanism
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The kinetics of the pyrolyses of two bromo esters have been investigated in a static system over the temperature range 379-419 deg C and pressure range 51-110 Torr.The reactions in seasoned vessels, and under maximum inhibition with the radical chain suppressor propene, are homogeneous, unimolecular, and follow a first-order rate law.The Arrhenius equations for these elimination processes were found to be as follows: for methyl 4-bromobutyrate, log k1 (s-1) = (13.38 +/- 0.59) - (216.7 +/- 7.6)kJ mol-1 (2.303RT)-1; for methyl 5-bromovalerate, log k1 (s-1) = (13.83 +/- 0.17) - (228.9 +/- 2.3) kJ mol-1 (2.303RT)-1.The anchimeric assistante of the carbomethoxy substituent is determinant in the elimination process, where dehydrobromination product and lactone formation result from an intimate ion pair type of mechanism.The partial rates toward each of the primary products have been determined, reported, and discussed.The present work provides further support of the intimate ion pair mechanism in the gas-phase pyrolysis of special types of organic halides.
- Chuchani, Gabriel,Dominguez, Rosa M.
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p. 1883 - 1887
(2007/10/02)
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- Esterification, Etherification, and Aldol Condensation Using Cathodically-Generated Organic Olate Anions
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Cathodic methods for the esterification of carboxylic acids and the etherification of phenol and benzenethiol under mild conditions were developed.The esterification was successfully carried out at room temperature by the reaction of alkylating reagents with cathodically-generated quaternary ammonium carboxylates.The etherification was similarly achieved using electrogenerated quaternary ammonium phenolate and halonitrobenzenes.A hindered phenolate anion cathodically-generated from 2,6-di-t-butyl-p-cresol remarkably promoted aldol condensation of aromatic ketones and aldehydes, and allowed subsequent Michael reaction to provide efficiently symmetrical 1,5-diketones.
- Fuchigami, Toshio,Awata, Takeshi,Nonaka, Tsutomu,Baizer, Manuel M.
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p. 2873 - 2880
(2007/10/02)
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- ESTERIFICATION AT ROOM TEMPERATURE: A MIXING AFFAIR ONLY
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Carboxylic acids in absolute alcohols, on treatment with thionyl chloride at room temperature give good yields of corresponding esters.
- Kumar, Baldev,Verma, Raman
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p. 1359 - 1364
(2007/10/02)
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- On the Regioselectivity of Free Radical Processes; Reactions of Benzoyloxy, Phenyl and t-Butoxy Radicals with Some α,β-Unsaturated Esters
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The reactions of three electrophilic radicals, benzoyloxy, and t-butoxy, have been examined with a series of α,β-unsaturated esters; methyl acrylate, methyl methacrylate, and methyl crotonate.For the three monomers the ratio of hydrogen abstraction to double bond addition was found to increase and the ratio of head against tail addition to decrease in the series: benzoyloxy; phenyl; t-butoxy.Relative rates for these reactions have been determined and the factors influencing the mode of reaction are discussed.
- Moad, Graeme,Rizzardo, Ezio,Solomon, David H.
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p. 1573 - 1588
(2007/10/02)
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- Reactions of Cyclic Anhydrides: Part VI - Transesterification of Maleanilic and Fumaranilic Acids with Phosphorus Pentoxide-Alkanol
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Mixed phosphorus esters obtained from alkanols and phosphorus pentoxide furnish the corresponding esters in 80-90percent yield when refluxed with maleanilic and fumaranilic acids.
- Wagh, S. B.,Balasubramaniyan, P.,Balasubramaniyan, V.
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p. 577 - 578
(2007/10/02)
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