- Production of renewable lubricants: Via self-condensation of methyl ketones
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Self-condensation of biomass-derived methyl ketones catalyzed by solid bases or acids produces corresponding cyclic trimers exclusively in excellent yields. Condensates containing 24-45 carbon atoms are shown to be suitable lubricant base-oils after the removal of residual unsaturation and oxygen. Properties of cycloalkanes produced from biomass are very similar to those of conventional lubricant base-oils. The process reported here offers an environmentally benign alternative to the current non-selective production of lubricant base-oils from α-olefins, and avoids the production of corrosive waste products.
- Balakrishnan, Madhesan,Arab, George E.,Kunbargi, Omar B.,Gokhale, Amit A.,Grippo, Adam M.,Toste, F. Dean,Bell, Alexis T.
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Read Online
- H-BPin/KOtBu Promoted Activation of Cobalt Salt to a Heterotopic Catalyst for Highly Selective Cyclotrimerization of Alkynes
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A mixture of HBPin with KOtBu was found to activate cobalt salt to form a heterotopic cobalt species that is highly active for catalytic intermolecular trimerization of alkynes. This protocol affords 1,2,4-regioisomers in good yields with high regioselectivities under mild conditions. These salient features, together with the operational simplicity and high efficiency, as well as obviating the use of any costly and/or air sensitive ligands, renders the protocol promising for practical applications.
- Song, Shuo,Li, Chuhan,Liu, Tianfen,Zhang, Panke,Wang, Xiaoming
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supporting information
p. 6925 - 6930
(2021/09/14)
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- Synthesis, characterization and catalytic application of some novel PNP-Ni(II) complexes: Regio-selective [2+2+2] cycloaddition reaction of alkyne
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Some novel Ni(II) complexes of PN(H)PPh, PN(Me)PiPr and PN(Me)PtBu ligands have been synthesized and characterized using standard analytical and spectroscopic methods such as 1H NMR, 31P NMR, elemental analysis, ESI-MS, UV-Visible spectroscopy and single-crystal X-ray crystallography. In the presence of silver triflate, complex [PN(H)PPhNiBr]2NiBr4 (5) activated the C?Cl bond of dichloromethane at room temperature and afford complex [PN(H)PPhNiCl]OTf (6). We have also performed alkyne [2+2+2] cycloaddition reaction using Ni(II) complexes and observed high regioselectivity of the products. The observed selectivity is well correlating with the electronic feature of alkynes. The [2+2+2] cycloaddition of electron rich alkynes produced 1,3,5-substituted benzene derivatives as a major product whereas the electron deficient alkynes produced 1,2,4-substituted benzene derivatives as a major product.
- Tamizmani, Masilamani,Sivasankar, Chinnappan
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- Silica-supported tungsten carbynes (≡SiO)xW(≡CH)(Me)y (x = 1, y = 2; X = 2, y = 1): New efficient catalysts for alkyne cyclotrimerization
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The activity of silica-supported tungsten carbyne complexes (≡SiO)xW(≡CH)(Me)y (x = 1, y = 2; x = 2, y = 1) toward alkynes is reported. We found that they are efficient precatalysts for terminal alkyne cyclotrimerization with high TONs. We also demonstrate that this catalyst species is active for alkyne cyclotrimerization without the formation of significant alkyne metathesis products. Additional DFT calculations highlight the importance of the W coordination sphere in supporting this experimental behavior.
- Riache, Nassima,Dery, Alexandre,Callens, Emmanuel,Poater, Albert,Samantaray, Manoja,Dey, Raju,Cavallo, Luigi,Basset, Jean-Marie,Hong, Jinhua,Li, Kun
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p. 690 - 695
(2015/06/01)
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- Short synthesis of methylenecyclopentenones by intermolecular Pauson-Khand reaction of allyl thiourea
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N,N,N′-Trimethylallylthiourea promotes the intermolecular Pauson-Khand reaction with alkynes in the presence of Co2(CO)8 and moderate pressure of CO followed by thiourea elimination allowing the formation of methylenecyclopentenone d
- Petrovski, ?eljko,Martins, Bruno M.R.,Afonso, Carlos A.M.
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supporting information; experimental part
p. 3356 - 3359
(2010/08/19)
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- Highly regioselective [2+2+2] cycloaddition of terminal alkynes catalyzed by titanium complexes of p-tert-butylthiacalix[4]arene
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Mono- and dinuclear titanium complexes of p-tert-butylthiacalix[4]arene were applied as a catalyst for [2+2+2] cycloaddition of terminal alkynes. They showed high catalytic activity and regioselectivity toward 1,3,5-trisubstituted benzenes over 1,2,4-trisubstituted isomers. The regioselectivity was rationalized in terms of the steric effect of the thiacalixarene skeleton and the coordination of the bridging sulfur atom to the titanium center.
- Morohashi, Naoya,Yokomakura, Katsuya,Hattori, Tetsutaro,Miyano, Sotaro
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p. 1157 - 1161
(2007/10/03)
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- 1,3,5-Trialkyl-2,4,6-triiodobenzenes: Novel x-ray contrast agents for gastrointestinal imaging
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Examination of the gastrointestinal (GI) tract has been performed for decades using barium sulfate. Although this agent has many recognized limitations including extreme radiopacity, poor intrinsic affinity for the GI mucosa, and very high density, no alternative contrast agents have emerged which produce comparable or better contrast visualization. In fact, the various techniques of the GI radiologic examination (i.e., single contrast, double contrast, biphasic) were developed to compensate for its limitations. Each of these techniques requires complex patient manipulation to achieve adequate mucosal coating or compression to overcome the marked radiopacity of barium sulfate in order to obtain a diagnostically useful examination. A series of novel radiopaque oils, the 1,3,5-trialkyl-2,4,6-triiodobenzenes, was designed to improve the efficacy, stability, and safety of barium formulations. These substances were prepared in two steps from 1,3,5- trichlorobenzene. Compound 17 (1,3,5-tri-n-hexyl-2,4,6-triiodobenzene), formulated as an oil-in-water emulsion, was found to be well-tolerated in rodents (mice, hamsters, rats) following acute oral and/or intraperitoneal administrations at 4 times the anticipated human clinical dose. No metabolism of 17 was detected in rat, hamster, dog, monkey, or human hepatic microsomes, suggesting the lack of oral toxicity was a consequence of poor absorption. In imaging experiments in dogs, emulsions of 17 have demonstrated excellent mucosal coating and improved radiodensity relative to barium sulfate suspensions. On the basis of the preliminary imaging and toxicity data, compound 17 was selected as a potential development candidate.
- Estep, Kimberly G.,Josef, Kurt A.,Bacon, Edward R.,Illig, Carl R.,Toner, John L.,Mishra, Dinesh,Blazak, William F.,Miller, Dennis M.,Johnson, David K.,Allen, Jack M.,Spencer, Andy,Wilson, Susan A.
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p. 1940 - 1948
(2007/10/03)
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- Regiospecific Synthesis of Aromatic Compounds via Organometallic Intermediates. 3. n-Alkyl-Substituted Benzene
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High molecular weight tri- and tetra-n-alkylbenzenes have been synthesized by the cross-coupling of the appropriate chlorinated benzenes with long-chain n-alkylmagnesium bromides using (1,2-bis(diphenylphosphino)ethane)nickel(II)chloride as catalyst.The reactions proceeded without any positional scrambling or alkyl group isomerization.A new method is described for the preferential substitution of one chlorine atom by an n-alkyl group in 1,3,5-trichlorobenzene.The reaction between an n-alkylmagnesium bromide and 1,3,5-trichlorobenzene catalyzed by Nickelacetylacetonate at low temperature and in tetrahydrofuran solvent favors monosubstitution.The cross-coupling reactions of these n-alkyldichlorobenzenes with other n-alkylmagnesium bromides, in the presence of NiCl2(dppe), proceeded at a much slower rate than those of 1,3,5-trichlorobenzene to yield the asymmetric 1,3,5-tri-n-alkylbenzenes.
- Eapen, Kalathil C.,Dua, Sujan S.,Tamborski, Christ
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p. 478 - 482
(2007/10/02)
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- Synthesis of 1,3,5-Trialkylbenzenes from Anils of Methyl Alkyl Ketones
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Besides the previously observed 2,2,4-trialkyl-1,2-dihydroquinolines, a mixture of 1,3,5-trialkylbenzenes and 1-methyl-2,3,5-trialkylbenzenes was obtained in up to 50percent yields when methyl alkyl ketones, aniline, and an acidic catalyst, such as hydrogen chloride, were heated to 180 deg C and the water was removed as formed.The reaction is thought to proceed through an α,β,γ,δ-unsaturated anil intermediate, but the corresponding α,β,γ,δ-unsaturated imines and aliphatic amines did not give trialkylbenzenes.
- Layer, Robert W.
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p. 4552 - 4555
(2007/10/02)
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