- Copolymerization of carbon dioxide and propylene oxide by several metallosalen-based bifunctional catalysts
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A series of new metallosalen-based bifunctional catalysts with Co(III), Cr(III), Fe(III), Mn(III), and Ni(III) were synthesized for the first time, and a detailed study on the mechanism of the copolymerization of CO2 and propylene oxide (PO) was performed. Meanwhile, the impact factors of the reaction conditions (metal cations, temperature, CO2 pressure, and reaction time) on catalytic activity and selectivity were investigated. The results indicated that, with the increase of temperature, both the catalyst efficiency and the molecular weight of the copolymer decrease for all the five complexes. The salen-Co(III) complex demonstrated higher activity under mild conditions: reaction temperature at 30 °C, copolymerization time of 24 hr, and 2 MPa of CO2 pressure. The DSC curve indicated that the PPC by the salen-Co(III) complex has the highest Tg of 46.19 °C. DTGA curves demonstrated that there were two thermal degradation peaks: the first is for the ester bond, and the second is for the C?C bond.
- Zhu, Wenkai,Du, Longchao,Qian, Siyu,Yang, Qingsong,Song, Wanjie
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Read Online
- The salen based chemosensors for highly selective recognition of Zn2+ ion
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Two novel salen based chemosensors have been successfully synthesized. UV–vis absorption, fluorescence emission spectroscopy and cyclic voltammetry (CV) were exploited to investigate their recognition toward various metal ions, including Na+, K+, Mg2+, Al3+, Zn2+, Ag+, Pb2+, Co2+, Li+, Ba2+, Ca2+, Cd2+, La3+, Cu2+ and Mn2+ ions. The results indicated that the sensor L1 and L2 exhibited highly selective and sensitive recognition for Zn2+ ions. The binding stoichiometry ratio of L1-Zn2+/L2-Zn2+ were recognized as 4:1 by the method of Job's plot. Meanwhile, this investigation is confirmed by 1H NMR. These results indicated that L1 and L2 can be applied as chemosensor for the detection of Zn2+ ion.
- Zhu, Wenkai,Du, LongChao,Li, Wensheng,Zuo, Jinyan,Shan, Jingrui
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p. 501 - 509
(2018/06/14)
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- Oxidative 1,2-Difunctionalization of Ethylene via Gold-Catalyzed Oxyarylation
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Under the conditions of oxidative gold catalysis, exposure of ethylene to aryl silanes and alcohols generates products of 1,2-oxyarylation. This provides a rare example of a process that allows catalytic differential 1,2-difunctionalization of this feedstock chemical.
- Harper, Matthew J.,Emmett, Edward J.,Bower, John F.,Russell, Christopher A.
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p. 12386 - 12389
(2017/09/22)
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- Easy eco-friendly phenonium ion production from phenethyl alcohols in dimethyl carbonate
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An efficient and simple one-pot procedure for selective etherification of 2-aryl-ethylalcohols has been achieved through Amberlyst 15-catalyzed reaction in dimethyl carbonate (DMC). Moreover, the polymer catalyst could be recovered and reused with no effect on its activity. The reaction mechanism involves the formation of phenonium ion which has been demonstrated by a C-C bond forming reaction. Theoretical studies are in agreement with and thus explain experimental results.
- Barontini,Proietti Silvestri,Nardi,Bovicelli,Pari,Gallucci,Spezia,Righi
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supporting information
p. 5004 - 5006
(2013/08/28)
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- Cross-coupling of alkyl halides with aryl or alkyl Grignards catalyzed by dinuclear Ni(ii) complexes containing functionalized tripodal amine-pyrazolyl ligands
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Structurally distinctive dinuclear Ni(ii) complexes with furan or thiophene tethered amine-pyrazolyl tripodal hybrid ligands have been synthesized and crystallographically characterized. All complexes are catalytically active towards cross-coupling of aryl/alkyl Grignard reagents with β-H containing alkyl halides at room temperature in the presence of N,N,N',N'- tetramethylethylenediamine (TMEDA). The catalytic efficacy of the complexes is dependent on the tether substituent at the central amine. Two species, Ni(ii) TMEDA and Mg(ii) TMEDA complexes, have been isolated from the catalytic reaction mixtures under different conditions. Some ligand-stabilized Ni(ii) and Mg(ii) bimetallic species have also been identified in the ESI-MS spectra.
- Xue, Fei,Zhao, Jin,Hor, T. S. Andy
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p. 5150 - 5158
(2013/04/10)
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- Synthesis of ethers from esters via Fe-catalyzed hydrosilylation
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Triiron dodecacarbonyl allows for the selective reduction of esters into the corresponding ethers. This protocol has a wide substrate scope. In addition, cholesteryl pelarogonate has been reduced under the reaction conditions with an excellent yield.
- Das, Shoubhik,Li, Yuehui,Junge, Kathrin,Beller, Matthias
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supporting information
p. 10742 - 10744
(2013/01/15)
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- Suzuki-Miyaura cross-coupling of potassium alkoxyethyltrifluoroborates: Access to aryl/heteroarylethyloxy motifs
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The introduction of an alkoxyethyl moiety onto aromatic substructures has remained a long-standing challenge for synthetic organic chemists. The main reasons are the inherent instability of alkoxyethylmetallic species and the lack of general procedures to access them. A new method utilizing a cross-coupling strategy based on the exceptional properties of organotrifluoroborates has been developed, and the method allows an easy and efficient installation of this unit on a broad range of aryl and heteroaryl bromides.
- Fleury-Bregeot, Nicolas,Presset, Marc,Beaumard, Floriane,Colombel, Virginie,Oehlrich, Daniel,Rombouts, Frederik,Molander, Gary A.
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p. 10399 - 10408
(2013/01/15)
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- RENIN INHIBITORS
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Renin inhibitors, which are spirocyclic piperidine amides, of structural formula (I) and pharmaceutical compositions thereof useful in the treatment of cardiovascular diseases and renal insufficiency, wherein n, for each instance in which it occurs, is independently 0, 1, or 2; R1 is hydrogen, C1-6 -alkyl or C3-6 -cycloalkyl, wherein said C1-6 -alkyl or C3-6 -cycloalkyl group can be independently substituted with 1-3 halogens; A is (i) a five- or six-membered saturated or unsaturated heterocyclic or carbocyclic monocyclic ring or (ii) a five- or six-membered saturated or unsaturated heterocyclic or carbocyclic ring which is fused to another five- or six-membered saturated or unsaturated heterocyclic or carbocyclic ring, V is a bond or -(C=O)-, -CH(OH)-, -CH2- or =CH-; U is a bond or -CH2-, or for the case when V is =CH-, U is -CH=; X is =CH-, =CF-, =C(OR3)-, or -C=O-; and Y is =CH-, =CF-, =N-, or for the case when X is -C=O-, Y is -N(R3)-.
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- Indium(i)-catalyzed alkyl-allyl coupling between ethers and an allylborane
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An efficient method for alkyl-allyl cross-coupling between ethers and a 9-BBN-derived allylborane catalyzed by indium(i) triflate has been developed. The allylborane proved to be essential to obtain the desired products in high yields. The reaction displayed good substrate scope including high functional group tolerance. The Royal Society of Chemistry 2011.
- Dao, Hai Thanh,Schneider, Uwe,Kobayashi, Shu
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supporting information; experimental part
p. 692 - 694
(2011/03/22)
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- Functional group tolerant Kumada-Corriu-Tamao coupling of nonactivated alkyl halides with aryl and heteroaryl nucleophiles: Catalysis by a nickel pincer complex permits the coupling of functionalized Grignard reagents
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A nickel(II) pincer complex [(MeNN2)NiCl] (1) catalyzes Kumada-Corriu-Tamao cross coupling of nonactivated alkyl halides with aryl and heteroaryl Grignard reagents. The coupling of octyl bromide with phenylmagnesium chloride was used as a test reaction. Using 3 mol % of 1 as the precatalyst and THF as the solvent, and in the presence of a catalytic amount of TMEDA, the coupling product was obtained in a high yield. The reaction conditions could be applied to cross coupling of other primary and secondary alkyl bromides and iodides. The coupling is tolerant to a wide range of functional groups. Therefore, alkyl halides containing ester, amide, ether, thioether, alcohol, pyrrole, indole, furan, nitrile, conjugated enone, and aryl halide moieties were coupled to give high isolated yields of products in which these units stay intact. For the coupling of ester-containing substrates, O-TMEDA is a better additive than TMEDA. The reaction protocol proves to be efficient for the coupling of Knochel-type functionalized Grignard reagents. Thus aryl Grignard reagents containing electron-deficient and/or sensitive ester, nitrile, amide, and CF3 substituents could be successfully coupled to nonactivated and functionalized alkyl iodides. The catalysis is also efficient for the coupling of alkyl iodides with functionalized heteroaryl Grignard reagents, giving rise to pyridine-, thiophene-, pyrazole-, furan-containing molecules with additional functionalities. Concerning the mechanism of the catalysis, [(MeNN2)Ni-(hetero)Ar] was identified as an intermediate, and the activation of alkyl halides was found to take place through a radical-rebound process.
- Vechorkin, Oleg,Proust, Valerie,Hu, Xile
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supporting information; experimental part
p. 9756 - 9766
(2011/03/19)
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- A new type of abnormal reimer-tiemann reaction
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The treatment of l, 2, 3, 4, 4a, 9b-hexahydro-3, 8-dihydroxy-7-methoxy-9b-(2'-methoxyethyl)dibenzofuran with chloroform and aqueous potassium hydroxide under conventional Reimer-Tiemann reaction conditions resulted in the replacement of the 7-methoxyl group by a carbaldehyde one. A choice between alternative pathways for this novel displacement has been facilitated by examination of the behaviour of the corresponding 7-trideuteromethoxy compound. Dichlorocarbene attack at position 7 rather than at the unsubstituted position 9 is shown to be due to steric encumbrance at the latter site.
- Bird,Bronw,Chan
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p. 4685 - 4690
(2007/10/02)
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- Chemistry of the Coccoidea. X Synthesis of the Xantholaccaic Acid B System and of Related Compounds
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Xantholaccaic acid B dimethyl ester pentamethyl ether (6) and some related anthraquinones have been synthesized by regiospecific Diels-Alder addition of the highly functionalized dienes (12) and (27) successively to 2,6-dichloro-1,4-benzoquinone.This is the first synthesis of the β-arylanthraquinone skeleton characteristic of the water-soluble dyestuffs from lac insects.
- Cameron, Donald W.,Feutrill, Geoffrey I.,Perlmutter, Patrick
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p. 1469 - 1480
(2007/10/02)
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