18707-60-3Relevant articles and documents
The role of neutral donor ligands in the isoselective ring-opening polymerization of: Rac -β-butyrolactone
Dong, Xiang,Robinson, Jerome R.
, p. 8184 - 8195 (2020/09/07)
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
Aldehydes as potential acylating reagents for oxidative esterification by inorganic ligand-supported iron catalysis
Yu, Han,Wang, Jingjing,Wu, Zhikang,Zhao, Qixin,Dan, Demin,Han, Sheng,Tang, Jiangjiang,Wei, Yongge
supporting information, p. 4550 - 4554 (2019/08/21)
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.
Chain Multiplication of Fatty Acids to Precise Telechelic Polyethylene
Witt, Timo,H?u?ler, Manuel,Kulpa, Stefanie,Mecking, Stefan
supporting information, p. 7589 - 7594 (2017/06/13)
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.
Ligand-controlled insertion regioselectivity accelerates copolymerisation of ethylene with methyl acrylate by cationic bisphosphine monoxide-palladium catalysts
Mitsushige, Yusuke,Carrow, Brad P.,Ito, Shingo,Nozaki, Kyoko
, p. 737 - 744 (2015/12/26)
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.
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
Wessjohann, Ludger A.,Wild, Harry,Ferreira, Leonildo A.,Schrekker, Henri S.
, p. 674 - 679 (2016/07/19)
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.
Versatile PdTe/C catalyst for liquid-phase oxidations of 1,3-butadiene
Kuznetsova,Zudin,Kuznetsova,Zaikovskii,Kajitani,Utsunomiya,Takahashi
, p. 30 - 38 (2016/01/12)
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%).
Multimetallic Ir-Sn3-catalyzed substitution reaction of π-activated alcohols with carbon and heteroatom nucleophiles
Maity, Arnab Kumar,Chatterjee, Paresh Nath,Roy, Sujit
, p. 942 - 956 (2013/07/25)
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.
Liberation of methyl acrylate from metallalactone complexes via M-O ring opening (M = Ni, Pd) with methylation agents
Lee, S. Y. Tina,Ghani, Amylia Abdul,D'Elia, Valerio,Cokoja, Mirza,Herrmann, Wolfgang A.,Basset, Jean-Marie,Kuehn, Fritz E.
supporting information, p. 3512 - 3517 (2013/11/06)
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.
Manganese phthalocyanine immobilized on silica gel: Efficient and recyclable catalyst for single-step oxidative esterification of aldehydes with alcohols
Sharma,Gulati, Shikha
, p. 291 - 303 (2012/10/30)
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.
Practical, catalytic enantioselective hydrogenation to synthesize N -unprotected β-amino esters
Matsumura, Kazuhiko,Zhang, Xiaoyong,Hori, Kiyoto,Murayama, Toshiyuki,Ohmiya, Tadamasa,Shimizu, Hideo,Saito, Takao,Sayo, Noboru
experimental part, p. 1130 - 1137 (2012/01/03)
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.
