- Ligand-controlled cobalt-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes
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The Co-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes were realized by a ligand-controlled strategy. The remote hydroboration with dcype provided borylethers, while xantphos favored the formation of silyl enol ethers.
- Huang, Jiaxin,Li, Jie,Yang, Wen,Zhang, Kezhuo,Zhao, Pei,Zhao, Wanxiang
-
supporting information
p. 302 - 305
(2022/01/03)
-
- Oxidative esterification of alcohols by a single-side organically decorated Anderson-type chrome-based catalyst
-
The direct esterification of alcohols with non-noble metal-based catalytic systems faces great challenges. Here, we report a new chrome-based catalyst stabilized by a single pentaerythritol decorated Anderson-type polyoxometalate, [N(C4H9)4]3[CrMo6O18(OH)3C{(OCH2)3CH2OH}], which can realize the efficient transformation from alcohols to esters by H2O2oxidation in good yields and high selectivity without extra organic ligands. A variety of alcohols with different functionalities including some natural products and pharmaceutical intermediates are tolerated in this system. The chrome-based catalyst can be recycled several times and still keep the original configuration and catalytic activity. We also propose a reasonable catalytic mechanism and prove the potential for industrial applications.
- Wang, Jingjing,Jiang, Feng,Tao, Chaofu,Yu, Han,Ruhlmann, Laurent,Wei, Yongge
-
supporting information
p. 2652 - 2657
(2021/04/21)
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- Second-Generation meta-Phenolsulfonic Acid-Formaldehyde Resin as a Catalyst for Continuous-Flow Esterification
-
A second-generation m-phenolsulfonic acid-formaldehyde resin (PAFR II) catalyst was prepared by condensation polymerization of sodium m-phenolsulfonate and paraformaldehyde in an aqueous H2SO4 solution. This reusable, robust acid resin catalyst was improved in both catalytic activity and stability, maintaining the characteristics of the previous generation catalyst (p-phenolsulfonic acid-formaldehyde resin). PAFR II was applied in the batchwise and continuous-flow direct esterification without water removal and provided higher product yields in continuous-flow esterification than any other commercial ion-exchanged acid catalyst tested.
- Hu, Hao,Ota, Hajime,Baek, Heeyoel,Shinohara, Kenta,Mase, Toshiaki,Uozumi, Yasuhiro,Yamada, Yoichi M. A.
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supporting information
p. 160 - 163
(2020/01/02)
-
- The role of neutral donor ligands in the isoselective ring-opening polymerization of: Rac -β-butyrolactone
-
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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- Formal synthesis of borrelidin: A highly enantio- and diastereoselective access to the Morken's C2-C12 intermediate
-
In contrast to methyl and isobutyl phenyl sulfone, condensing under basic conditions higher alkyl sulfones and trans-2,3-epoxy-butanol 13c (or its O-benzyl and O-silyl derivatives) proved unfeasible, a difficulty that was overcome by using mono ethers of trans-2,3-epoxy-butane-1,4-diol 35c as the electrophilic reagents. Thus, adding excess BuLi to a mixture of the benzyl ether 35b and sulfone ent-12a, a stereodiad sulfone prepared in pure state from the R-Roche ester, via the O-trityloxy-sulfone ent-12c (X-ray), gave, after elimination by column chromatography of the side-formed regioisomer, a diolsulfone that was next converted to sulfone 20 by means of conventional functional-group modifications. Reacting like-wise this sulfone with the parent O-PMB derivative 35a, and then proceeding to the same purification process and function adjustment, delivered the title fragment in virtually pure state.
- Gembus, Vincent,Karmazin, Lydia,Uguen, Daniel,Zoller, Thomas
-
supporting information
p. 359 - 380
(2019/02/25)
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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
-
supporting information
p. 4550 - 4554
(2019/08/21)
-
- 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
-
supporting information
p. 7589 - 7594
(2017/06/13)
-
- NOVEL SINGLE STEP ESTERIFICATION PROCESS OF ALDEHYDES USING A HETEROGENEOUS CATALYST
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The present invention relates to a novel simple, efficient and single-step process for esterification of aldehydes using a heterogeneous catalyst with high yields. More particularly, the present invention relates to a novel simple, efficient and single-step process for esterification of aldehydes using Titanium superoxide with greater than 80% yields.
- -
-
Page/Page column 16; 19
(2016/06/20)
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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
-
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
-
-
- Ligand-controlled insertion regioselectivity accelerates copolymerisation of ethylene with methyl acrylate by cationic bisphosphine monoxide-palladium catalysts
-
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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- Titanium superoxide-a stable recyclable heterogeneous catalyst for oxidative esterification of aldehydes with alkylarenes or alcohols using TBHP as an oxidant
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Titanium superoxide efficiently catalysed the oxidative esterification of aldehydes with alkylarenes or alcohols, under truly heterogeneous conditions, to afford the corresponding benzyl and alkyl esters in excellent yields. Mechanistic studies have established that this "one pot" direct oxidative esterification process proceeds through a radical pathway, proven by a FTIR spectral study of a titanium superoxide-aldehyde complex as well as spin trapping experiments with TEMPO. The intramolecular version of this protocol has been successfully demonstrated in the concise synthesis of 3-butylphthalide, an anti-convulsant drug.
- Dey, Soumen,Gadakh, Sunita K.,Sudalai
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p. 10631 - 10640
(2015/11/17)
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- Asymmetric cascade reaction to allylic sulfonamides from allylic alcohols by palladium(II)/base-catalyzed rearrangement of allylic carbamates
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A regio- and enantioselective tandem reaction is reported capable of directly transforming readily accessible achiral allylic alcohols into chiral sulfonyl-protected allylic amines. The reaction is catalyzed by the cooperative action of a chiral ferrocene palladacycle and a tertiary amine base and combines high step-economy with operational simplicity (e.g. no need for inert-gas atmosphere or catalyst activation). Mechanistic studies support a Pd II-catalyzed [3,3] rearrangement of allylic carbamates - generated in situ from the allylic alcohol and an isocyanate - as the key step, which is followed by a decarboxylation.
- Bauer, Johannes Moritz,Frey, Wolfgang,Peters, Rene
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supporting information
p. 7634 - 7638
(2014/08/05)
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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)
-
- 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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- Controlled acrylate insertion regioselectivity in diazaphospholidine- sulfonato palladium(II) complexes
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Diazaphospholidine-sulfonato Pd(II) complexes [{κ2-P,O-(N- Ar2C2H4N2P)C6H 4SO3}PdMe(L)] 1-L (L = dmso, pyridine, lutidine, or μ-LiCl(solvent); 1a: Ar = Ph, 1b: Ar = 2-MeC6H4, 1c: Ar = 2-MeOC6H4, 1d: Ar = 2,4,6-Me3C 6H2, 1e: Ar = 2,6-iPr2C6H 3, 1f: Ar = 2,6-(p-tolyl)2C6H3) were prepared and structurally characterized. The regioselectivity of methyl acrylate (MA) insertion into the Pd-Me bond is entirely inverted from >93% 1,2-insertion for bulky substituents (1d-f, yielding the insertion products [(PO)Pd{κ2-C,O-CH2CHMeC(O)OMe], 12) to the usual electronically controlled 2,1-insertion (>95%) for the less bulky Ar = Ph (1a, yielding the insertion product [(PO)Pd{κ2-C,O- CHEtC(O)OMe], 11, and β-H elimination product methyl crotonate). DFT studies underline that this is due to a more favorable insertion transition state (2,1- favored by 12 kJ mol-1 over 1,2- for 1a) vs destabilization of the 2,1-insertion transition state in 1d,e. By contrast, MA insertion into the novel isolated and structurally characterized hydride and deuteride complexes [{κ2-P,O-(N-Ar2C 2H4N2P)C6H4SO 3}PdR(lutidine)] (Ar = 2,6-iPr2C6H3; 9e: R = H, 10e: R = D) occurs 2,1-selectively. This is due to the insertion occurring from the isomer with the P-donor and the olefin in trans arrangement, rather than the insertion into the alkyl from the cis isomer in which the olefin is in proximity to the bulky diazaphospholidine. 1a-f are precursors to active catalysts for ethylene polymerization to highly linear polyethylene with M n up to 35 000 g mol-1. In copolymerization experiments, norbornene was incorporated in up to 6.1 mol % into the polyethylene backbone.
- Wucher, Philipp,Roesle, Philipp,Falivene, Laura,Cavallo, Luigi,Caporaso, Lucia,Goettker-Schnetmann, Inigo,Mecking, Stefan
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p. 8505 - 8515
(2013/02/23)
-
- 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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- The asymmetric aza-claisen rearrangement: development of widely applicable pentaphenylferrocenyl palladacycle catalysts
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Systematic studies have been performed to develop highly efficient catalysts for the asymmetric aza-Claisen rearrangement of trihaloacetimidates. Herein, we describe the stepwise development of these catalyst systems involving four different catalyst generations finally resulting in the development of a planar chiral pentaphenylferrocenyl oxazoline palladacycle. This complex is more reactive and has a broader substrate tolerance than all previously known catalyst systems for asymmetric aza-Claisen rearrange-ments. Our investigations also reveal that subtle changes can have a big impact on the activity. With the enhanced catalyst activity, the asymmetric aza-Claisen rearrangement has a very broad scope: the methodology not only allows the formation of highly enantioenriched primary allylic amines, but also secondary and tertiary amines; al-lylic amines with N-substituted quaternary stereocenters are conveniently accessible as well. The reaction conditions tolerate many important functional groups, thus providing stereoselective access to valuable functionalized building blocks, for example, for the synthesis of unnatural amino acids. Our results suggest that face-selective olefin coordination is the enantioselectivitydetermining step, which is almost exclusively controlled by the element of planar chirality.
- Fischer, Daniel F.,Barakat, Assem,Xin, Zhuo-Qun,Weiss, Matthias E.,Peters, Rene
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supporting information; scheme or table
p. 8722 - 8741
(2010/03/31)
-
- Impact of solvent polarity on n-heterocyclic carbene-catalyzed β-protonations of homoenolate equivalents
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N-Heterocyclic carbenes have been demonstrated to react through divergent pathways under the same conditions. Experimental and computational evidence demonstrates that the ability to favor generation of homoenolate equivalents from α,β-unsaturated aldehyd
- Maki, Brooks E.,Patterson, Eric V.,Cramer, Christopher J.,Scheidt, Karl A.
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supporting information; experimental part
p. 3942 - 3945
(2009/12/06)
-
- The detection of PHIP effects allows new insights into the mechanism of olefin isomerisation during catalytic hydrogenation
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PHIP (parahydrogen-induced polarisation) effects in the 1H NMR spectra of the products of Rh-complex-catalysed alkyne hydrogenation brings to light the fact that the cis-trans isomerisation of the formed olefin occurs through the formation of a σ-bonded intermediate stabilised by the reversible addition of a hydrogen molecule at the metal centre. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Viale, Alessandra,Santelia, Daniela,Napolitano, Roberta,Gobetto, Roberto,Dastru, Walter,Aime, Silvio
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experimental part
p. 4348 - 4351
(2009/02/08)
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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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- Ionic liquids as powerful solvent media for improving catalytic performance of silyl borate catalyst to promote Diels-Alder reactions
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(Chemical Equation Presented) Use of the acidic chloroaluminate ionic liquid, including the recycled ones, can improve the catalytic activity of the toluene-coordinated silyl borate in enhancing rates, stereo-selectivities, and yields of Diels-Alder reactions.
- Kumar, Anil,Pawar, Sanjay S.
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p. 8111 - 8114
(2008/03/11)
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- The first insoluble polymer-bound palladium complexes of 2-pyridyldiphenylphosphine: Highly efficient catalysts for the alkoxycarbonylation of terminal alkynes
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Palladium complexes of 2-pyridyldiphenylphosphine anchored on polystyrene, polymethylmethacrylate and styrene-methylmethacrylate copolymer form highly active heterogeneous catalysts for the alkoxycarbonylation of terminal alkynes with activities approaching those obtained under homogeneous conditions. The Royal Society of Chemistry 2006.
- Doherty, Simon,Knight, Julian G.,Betham, Michael
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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)
-
- Nickel-catalyzed [3+1+1] cycloaddition reactions of alkenyl Fischer carbene complexes with methylenecyclopropanes
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Methylenecyclopentanones were synthesized by the nickel-catalyzed [3+1+1] cycloaddition reactions of alkenyl Fischer carbene complexes with methylenecyclopropanes. The methylenecyclopropane was transformed into the C2-symmetric bis-cyclopentapyridazine derivative by reacting with p-toluenesulfonyl hydrazine.
- Kamikawa, Ken,Shimizu, Yasunori,Takemoto, Shin,Matsuzaka, Hiroyuki
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p. 4011 - 4014
(2007/10/03)
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- Stereoselective debromination and selective reduction of vic-dibromides with nickel boride
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A simple procedure is reported for the stereoselective debromination of vic-dibromides with nickel boride at ambient temperature. Debromination with concomitant reduction of vic-dibromides to give dihydro products in a one-pot reaction is also reported. α,β-Dibromoketones can also be converted to their corresponding alcohols.
- Khurana, Jitender M.,Kandpal, Bhaskar M.,Kukreja, Gagan,Sharma, Purnima
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p. 1019 - 1023
(2007/10/03)
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- Hydrophobic effects in a simple Diels-Alder reaction in water
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The endo/exo ratio for a simple Diels-Alder reaction carried out in water has been used to argue that hydrophobic effects can dominate the geometries of the transition states.
- Sarma, Diganta,Pawar, Sanjay S.,Deshpande, Suvarna S.,Kumar, Anil
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p. 3957 - 3958
(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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- Dichloroindium hydride (Cl2InH): A convenient reagent for stereoselective reduction of vic-dibromides to (E)-alkenes
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Dichloroindium hydride (Cl2InH) generated in situ from the combination of a catalytic amount of indium(III) chloride and sodium borohydride in acetonitrile reduces activated vic-dibromides to the corresponding (E)-alkenes in excellent yields.
- Ranu, Brindaban C.,Das, Arijit,Hajra, Alakananda
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p. 1012 - 1014
(2007/10/03)
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- Peroxovanadium-catalyzed oxidative esterification of aldehydes
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The peroxovanadium species generated from V2O5 and hydrogen peroxide, which is liberated from peroxy salts such as sodium perborate (SPB) or sodium percarbonate (SPC), transform aldehydes directly into esters in an alcoholic medium. Monoesters of diols have been achieved directly in one pot from aldehydes. High catalytic turnover number combined with inexpensive, easily available reagents and innocuous side products from the reaction make it a suitable alternative for the synthesis of esters from aldehydes.
- Gopinath, Rangam,Barkakaty, Balaka,Talukdar, Bandana,Patel, Bhisma K.
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p. 2944 - 2947
(2007/10/03)
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- Selective ring-opening cross-metathesis of cycloolefins
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A catalytic method is provided for a ring-opening cross-metathesis reaction between a cycloolefinic substrate and a second olefinic reactant, wherein the catalyst used is a transition metal alkylidene complex substituted with an N-heterocyclic carbene ligand. The substrates are selected so that the rate of the cross-metathesis reaction of the second olefinic reactant, kCM, is greater than or equal to the rate of the ring-opening metathesis reaction, kRO. In this way, the predominant ROCM product is a monomer, dimer, and/or oligomer, but not a polymer. The invention additionally provides for selective production of an end-differentiated olefinic product, using trisubstituted cycloolefins as substrates and/or a subsequent cross-metathesis reaction following an initial ROCM step. The cycloolefinic substrates include low-strain olefins such as cyclohexene as well as higher strain olefins such as cyclooctene.
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- EXO- and endohormones. XXII1: Synthesis of methyl (2E,4Z)-2,4-decadienoate, the pheromone synergist of the bark beetle Pityogenes chalcographus
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The synthesis of methyl (2E,4Z)-2,4-decadienoate was based on a C 4 + C6 scheme. The coupling reaction took place between the 1-hexanale and phosphonium salt of methyl 1-bromocrotonate in a Wittig condensation. Methyl (2E,4Z)-2,4-decadienoate is a minor component of the sex pheromone of the bark beetle Pityogenes chalcographus.
- Maxim, Sanda,Ganscǎ, Lucia,Oprean, Ioan,Budae, Iuliana
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p. 543 - 544
(2007/10/03)
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- Stereocontrol of the Horner-Wadsworth-Emmons Reaction: Application to the Synthesis of HIV-1 Protease Inhibitors
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A systematic study on the Horner-Wadsworth-Emmons (HWE) reaction has shown that ethyl diphenylphosphonoacetate and methyl diphenylphosphonoacetate give a high excess of (Z)-alkenes. These reaction conditions were then used to prepare (Z)-ethyl-5-phenylpent-2-enoate, the corresponding (E)-isomer being prepared by standard Wittig chemistry. Reduction of each allylic ester, with diisobutylaluminium hydride (DIBAL), gave the allylic alcohols (15) and (19), respectively. Epoxidation of (15) and (19), under Sharpless conditions, gave separate samples of all four stereoisomers of 2,3-epoxy-5-phenylpentan-1-ol. Esterification of each isomer with Cbz-valine, under Mitsunobu conditions, provided (9)-(12) which were assayed against HIV protease. The cis series (9)-(10) proved to be significantly more potent than the trans (11)-12) and, within each of these series, the isomers derived from L-diisopropyltartrate [(9) and (11)] were the most active.
- Martyn, Derek C.,Hoult, Deborah A.,Abell, Andrew D.
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p. 391 - 396
(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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- Microwave enhanced esterification of α,β-unsaturated acids
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A rapid and efficient method for the synthesis of α,β-unsaturated esters by the esterification of the corresponding carboxylic acids using dry methanol in the presence of catalytic amount of concentrated sulphuric acid under microwave irradiation is reported.
- Mitra,De,Karchaudhuri
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p. 311 - 312
(2007/10/03)
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- Esterification in dry media using ferric perchlorate adsorbed on silica gel
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Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic grade silica gel in the presence of alcohol ( to be used for esterification ) produces a supported reagent, Fe(ClO4)3(ROH)6/SiO2. This reagent, has been found effective for the rapid and high yield of esters, on grinding in the presence of carboxylic acids using pestle and mortar in the solid state.
- Parmar, Anupama,Kaur, Jatinder,Goyal, Rita,Kumar, Baldev,Kumar, Harish
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p. 2821 - 2826
(2007/10/03)
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- Thermal isomerization of 1,3-dipolar cycloadducts of 3,4-dihydro-β-carboline 2-oxide
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The thermal isomerization of the 1,3-dipolar cycloadducts of 3,4-dihydro-β-carboline 2-oxide is studied using 1H-NMR spectroscopy. Stereoisomerizations of the cis or syn cycloadducts with dipolarophiles such as methyl crotonate, methyl cinnamate, and methyl methacrylate into the trans or anti cycloadducts are observed. On the other hand, regioisomerization of the 1-substituted cycloadduct with nitroethylene into the 2-substituted cycloadduct is also observed.
- Moriyama, Satoshi,Vallee, Yannick
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p. 1391 - 1395
(2007/10/03)
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- "Green" MMA; an environmentally benign and economically attractive process for the production of methyl methacrylate
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Over the last seven years Shell has developed a novel, economically attractive, and environmentally benign process for the production of methyl methacrylate (MMA). The process is based on the highly efficient Palladium-catalysed methoxycarbonylation of propyne (methylacetylene or MA) under mild, non-corrosive reaction conditions (temperature ca. 50°C, CO pressure ca. 10 bar) according to the equation: MeOH + CO + HC≡C-Me(MA) → H2C=C(Me)-C(O)OMe(MMA) The activity (> 20000 mol-MMA/mol-Pd.h) and selectivity (> 99%mol) of the homogeneous Pd catalyst are very high making a once-through process with minimal waste possible. The MA feedstock for the process, together with propadiene (PD), is separated from a steam-cracker C3 stream by extractive distillation with DMF. Subsequently, PD is removed from this MA + PD/DMF mixture and isomerized over a heterogeneous K2O/Al2O3 catalyst to yield additional MA. Crude MMA obtained from the methoxycarbonylation of MA can easily be purified by a 'topping and tailing' procedure to yield MMA of very high purity (> 99.99 w%). This article describes some of the R&D work carried out at the 'Koninklijke/Shell-Laboratorium, Amsterdam' which has enabled the design of a plant, based on this novel technology.
- Keijsper,Arnoldy,Doyle,Drent
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p. 248 - 255
(2007/10/03)
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- Iron carbonyl-promoted isomerization of olefin esters to their α,β-unsaturated esters: Methyl oleate and other examples
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Ultraviolet photolysis of stoichiometric amounts of methyl oleate and Fe(CO)5 in hexanes solvent at 0°C gives Fe(CO)3(η4-α,β-ester) in which the α,β-unsaturated ester isomer of methyl oleate is stabilized by η4-oxadiene π coordination of the olefin and ester carbonyl groups to the Fe(CO)3 unit. Treatment of the Fe(CO)3(η4-α,β-ester) with pyridine or CO liberates the free α,β-ester, methyl octadec-trans-2-enoate, in 70% yield. The Fe(CO)3 unit both catalyzes the olefin isomerization and stabilizes the α,β-unsaturated ester, which results in the formation of the α,β-ester in a yield far above that (3.5%) observed for simple catalyzed methyl oleate isomerization. The much smaller olefin esters, methyl 3-butenoate and ethyl 4-methyl-4-pentenoate, are isomerized under the same conditions to their α,β-unsaturated esters in 94 and 90% yields, respectively. The effects of reaction conditions on the yield, the use of Fe(CO)3(cis-cyclooctene)2 as a nonphotolytic catalyst, and the mechanism of this useful synthetic process are discussed.
- Shih, Kuo-Chen,Angelici, Robert J.
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p. 7784 - 7792
(2007/10/03)
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- Pyridine derived agents for cardiovascular diseases
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STR1 Compounds of formula (I) or a biolabile ester thereof, or a pharmaceutically acceptable salt of either, wherein Rl, R2, R3 and R4 are each independently selected from H or C1 -C4 alkyl; R5 is (CH2)m SO2 R6, (CH2)m NHSO2 R6 or (CH2)m NHCOR7 ; R6 and R7 are C1 -C6 alkyl, C1 -C3 perfluoroalkyl(CH2)n, C3 -C6 cycloalkyl(CH2)n, aryl(CH2)n or heteroaryl(CH2)n ; or R6 is NR8 R9 ; R8 is H or C1 -C4 alkyl; R9 is C1 -C6 alkyl, C3 -C6 cycloalkyl(CH2)n, aryl(CH2)n or heteroaryl(CH2)n ; or R8 and R9 together with the nitrogen atom to which they are attached form a 5- to 7-membered heterocyclic ring which may optionally incorporate a carbon-carbon double bond or a further hetero atom linkage selected from O, S, NH, N(C1 -C4 alkyl) and N(C1 -C5 alkanoyl), and which may optionally be substituted with one to three substituents each independently selected from C1 -C4 alkyl and C1 -C4 alkoxy, and which may optionally be benzo-fused; X is CH2, CHCH3, C(OH)CH3, C=CH2 or O; m is 0 or 1; n is 0, 1, 2 or 3; and Het is 3- or 4-pyridyl or 1-imidazolyl; with the proviso that when Het is 1-imidazolyl then X is CH2 or CHCH3, are combined thromboxane A2 synthetase inhibitors and thromboxane A2 /endoperoxide antagonists of utility in the treatment of disease conditions in which thromboxane A2 is a causative agent.
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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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- Ruthenium Complex-Catalyzed Carbonylation of Allylic Compounds
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Allylic alkyl carbonates are carbonylated under 40 atm of carbon monoxide at 100-120 deg C in the presence of a catalytic amount of Ru3(CO)12/1,10-phenanthroline to give α,β- or β,γ-unsaturated esters in good to high yields.For example, cinnamyl methyl carbonate afforded the corresponding β,γ-unsaturated esters, methyl trans-4-phenyl-3-butenoate (1) in 93percent yield.The regioselectivity in the carbonylation of crotyl methyl carbonate is unusual and it depends on the carbon monoxide pressure.The more sterically hindered carbon (γ-carbon) is predominantly carbonylated at 20-50 atm.When the reaction of cinnamyl methyl carbonate was performed at elevated temperature (150 deg C) without 1,10-phenanthroline, the dimer of 1, dimethyl 3-benzyl-2-(trans-2-phenylvinyl)glutarate, was obtained in 56percent yield.In the presence of secondary amines, allylic alkyl carbonates were carbonylated mainly at α-carbon to give α,β- or β,γ-unsaturated amides in high yields.
- Mitsudo, Take-aki,Suzuki, Nobuyoshi,Kondo, Teruyuki,Watanabe, Yoshihisa
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p. 7759 - 7765
(2007/10/02)
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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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- Substituted crotonates and fungicides containing them
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Substituted crotonates of the formula STR1 where R1 is alkyl, R2 is hydrogen, alkyl or alkoxy, X is halogen, cyano, trifluoromethyl, nitro, alkyl, alkoxy, phenyl, phenoxy, benzyloxy or hydrogen, m is from 1 to 5, and Y is methylenoxy, oxymethylene, ethylene, ethenylene, ethynylene or oxygen, and fungicides containing them.
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- Reactivity of Alkenes at a Diruthenium Centre: Combination with Methylen and Oxidative Activation
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The complex undergoes methylene-ethylene combiation on heating to give propene, and ethylene activation upon oxidation with Ag+ to give the μ-vinyl cation +; treatment of the latter with H- affords , which evolves propene more efficiently on heating.
- Doherty, Nancy M.,Howard, Judith A. K.,Knox, Selby A. R.,Terrill, Nicholas J.,Yates, Michael I.
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p. 638 - 640
(2007/10/02)
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