- Deacylative transformations of ketones via aromatization-promoted C–C bond activation
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Carbon–hydrogen (C–H) and carbon–carbon (C–C) bonds are the main constituents of organic matter. Recent advances in C–H functionalization technology have vastly expanded our toolbox for organic synthesis1. By contrast, C–C activation methods that enable editing of the molecular skeleton remain limited2–7. Several methods have been proposed for catalytic C–C activation, particularly with ketone substrates, that are typically promoted by using either ring-strain release as a thermodynamic driving force4,6 or directing groups5,7 to control the reaction outcome. Although effective, these strategies require substrates that contain highly strained ketones or a preinstalled directing group, or are limited to more specialist substrate classes5. Here we report a general C–C activation mode driven by aromatization of a pre-aromatic intermediate formed in situ. This reaction is suitable for various ketone substrates, is catalysed by an iridium/phosphine combination and is promoted by a hydrazine reagent and 1,3-dienes. Specifically, the acyl group is removed from the ketone and transformed to a pyrazole, and the resulting alkyl fragment undergoes various transformations. These include the deacetylation of methyl ketones, carbenoid-free formal homologation of aliphatic linear ketones and deconstructive pyrazole synthesis from cyclic ketones. Given that ketones are prevalent in feedstock chemicals, natural products and pharmaceuticals, these transformations could offer strategic bond disconnections in the synthesis of complex bioactive molecules.
- Xu, Yan,Qi, Xiaotian,Zheng, Pengfei,Berti, Carlo C.,Liu, Peng,Dong, Guangbin
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p. 373 - 378
(2019/05/22)
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- The Use of Ureates as Activators for Samarium Diiodide
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A novel mode of SmI2 activation has been developed using ureates as reaction promoters. Several ureates formed by treatment of the corresponding ureas with n-BuLi have been shown to activate SmI2 to a substantial extent toward the reduction of 1-chlorodecane. Complexes formed from SmI2 and various ureates have been shown to be useful for the reduction of a variety of organohalides, including substrates of low reactivity such as aryl fluorides. Because of ease of synthesis and low molecular weight, the conjugate base of triethylurea (TEU-) was of primary focus. Visible spectroscopy and reactivity data are consistent with the hypothesis that the same complex is being formed when SmI2 is combined with either 2 or 4 equiv of TEU-, in spite of the greater reactivity of SmI2/4 TEU- with some alkyl halides. We propose that the active reductant is an N,O chelate formed between SmI2 and 2 equiv of TEU-.
- McDonald, Chriss E.,Ramsey, Jeremy D.,McAtee, Christopher C.,Mauck, Joseph R.,Hale, Erin M.,Cumens, Justin A.
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p. 5903 - 5914
(2016/07/23)
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- From insertion to multicomponent coupling: Temperature dependent reactions of arynes with aliphatic alcohols
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The temperature dependent selectivity switch in the reaction of arynes with aliphatic alcohols in THF has been reported. At -20°C, arynes smoothly insert into the O-H bond of alcohols to form alkyl aryl ethers. Interestingly, at 60°C, a highly selective multicomponent coupling occurs with the solvent THF acting as the nucleophilic trigger affording (4-(alkoxy)butoxy)arenes.
- Thangaraj, Manikandan,Bhojgude, Sachin Suresh,Mane, Manoj V.,Biju, Akkattu T.
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supporting information
p. 1665 - 1668
(2016/01/30)
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- Recyclable heterogeneous copper oxide on alumina catalyzed coupling of phenols and alcohols with aryl halides under ligand-free conditions
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An efficient alumina-supported CuO-catalyzed O-arylation of phenols and aliphatic alcohols with various aryl as well as heteroaryl halides under ligand-free conditions are reported. This protocol provides a variety of diaryl ether and bis-diaryl ether motifs by reacting different aryl/aliphatic halides with differently substituted phenols and saturated alcohols in the presence of a catalytic amount of CuO on alumina and KOH as a base at moderate temperature under nitrogen atmosphere. The described methodology is simple, straightforward and efficient to afford the cross-coupled products in high yields under ligand-free conditions. The explored catalyst is inexpensive, air-stable and recyclable up to three cycles.
- Swapna, Kokkirala,Murthy, Sabbavarapu Narayana,Jyothi, Mocharla Tarani,Nageswar, Yadavalli Venkata Durga
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supporting information; experimental part
p. 5978 - 5988
(2011/10/05)
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- CuO nanoparticles catalyzed C-N, C-O, and C-S cross-coupling reactions: Scope and mechanism
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CuO nanoparticles have been studied for C-N, C-O, and C-S bond formations via cross-coupling reactions of nitrogen, oxygen, and sulfur nucleophiles with aryl halides. Amides, amines, imidazoles, phenols, alcohols and thiols undergo reactions with aryl iodides in the presence of a base such as KOH, Cs 2CO3, and K2CO3 at moderate temperature. The procedure is simple, general, ligand-free, and efficient to afford the cross-coupled products in high yield.
- Jammi, Suribabu,Sakthivel, Sekarpandi,Rout, Laxmidhar,Mukherjee, Tathagata,Mandai, Santu,Mitra, Raja,Saha, Prasenjit,Punniyamurthy, Tharmalingam
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supporting information; experimental part
p. 1971 - 1976
(2009/07/01)
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- Water insoluble composition of an aldoxime extractant and an equilibrium modifier
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Alternative equilibrium modifiers for use with aldoxime extractants, such as hydroxyl aryl aldoxime extractants, employed in the process for extraction of metal values, particularly copper values, in the extraction from aqueous solutions, in which the extractant and modifiers are employed in an organic solvent phase, the solvent being a water insoluble, water immiscible hydrocarbon solvent, such as a kerosene.
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- The Effect of Two Terminal Alkoxy Groups on the Mesomorphic Properties of 4,4'-Disubstituted Phenylthiobenzoates
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A select variety of homologs of the dialkoxyphenylthiobenzoates were prepared.Their mesomorphic properties were determined by hot-stage polarizing microscopy and compared with those for the analogous RO-R' and R-OR' thioesters and esters.Unlike
- Neubert, Mary E.,Ziemnicka-Merchant, Barbara,Jirousek, Michael R.,Laskos, Stanley J.,Leonhardt, Darrin,Sharma, Ram B.
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p. 209 - 240
(2007/10/02)
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- SYNTHETIC APPLICATION OF MICELLAR CATALYSIS. WILLIAMSON'S SYNTHESIS OF ETHERS
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A simple, rapid and efficient procedure for the preparation of di-alkyl, simple phenyl-alkyl and hindered phenyl-alkyl ethers has been developed.Based on the principle of micellar catalysis the method involves alkylation of the alkoxide or the phenoxide ion with an alkyl chloride at 80 deg C in the presence of cationic micelles.For the preparation of phenyl-alkyl ethers normal micelles were used, while for the di-alkyl ethers reverse micelles were more effective.By increasing the ionic strength of the solution the rate of formation of phenyl-alkyl ethers could be increased.
- Jursic, Branko
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p. 6677 - 6680
(2007/10/02)
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- ARENE COMPLEXES OF TRANSITION METALS IN REACTIONS WITH NUCLEOPHILIC REAGENTS. XVII. NUCLEOPHILIC SUBSTITUTION OF THE FLUORINE ATOM BY ALKOXY GROUPS, CATALYZED BY THE (η-BENZENE)(η-ETHYLTETRAMETHYLCYCLOPENTADIENYL)RHODIUM(III) DICATION, IN THE REACTION OF FLUOROARENES WITH ALCOHOLS
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Effective catalysis by the (2+)2 complex, discovered earlier in the case of methoxydefluorination, occurs during the nucleophilic substitution of a fluorine atom by a alkoxy groups in the reactions of fluoroarenes with a wide range of alcohols in the absence of alkalis.By means of fluorobenzene it was established that the accumulation rate of the ethers depends substantially on the structure of the nucleophile and increases in the following order: PhCH2OH -CH2OH ClCH2CH2OH = sec-C3H7OH, sec-C4H9OH, cyclo-C6H11OH HO)CH2)nOH (n = 3-5) iso-C4H9OH = AlkOH (Alk = Me, Et, Pr, Bu, Am).For the case of the production of the compounds C10H21OC6H5 and C16H33O-2,4,6-Me3C6H2 it was shown that higher alkyl aryl ethers can be synthesized with yields of 65-70percent, calculated on the fluoroarene, and up to 900percent calculated on the catalyst.By the synthesis of benzodioxane in the reaction of o-fluorophenol with 2-chloroethanol it was demonstrated that heterocyclic compounds can be obtained if bifunctional substrates and reagents are used.
- Goryunov, L. I.,Litvak, V. V.,Shteingarts, V. D.
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p. 354 - 358
(2007/10/02)
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- Synthesis and Liquid Crystalline Properties of 1-(trans-4-Alkylcyclohexylethyl)-4-Alkyl- and -4-Alkoxy-Benzenes, Their Ketone Precursors, and Some Lateral Fluoro-Derivatives
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The preparation of some 1-(trans-4-alkylcyclohexylethyl)-4-alkyl- and -4-alkoxy-benzenes, their methylenecarbonyl linked analogues and their laterally fluoro- and bromo-substituted derivatives is reported.Twenty-four inter-related compounds have been prepared and the trends in their transition temperatures are discussed.Both the melting points and clearing points for these compounds are relatively low and, in general, SB and SA phases predominate.The suitability of these compounds as additives to SC materials has been assessed using two SC hosts.Keywords: Mesogenic cyclohexylethanes, mesogenic ketones, fuoro-substitution of mesogens
- Gray, George W.,Lacey, David,Scrowston, Richard M.,Shenouda, Ibrahim G.,Toyne, Kenneth J.
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p. 101 - 116
(2007/10/02)
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- The Use of Silica Gel-Supported Ionenes as Reagents and Catalysts for Several Substitution Reactions in Toluene
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Several ionene bromides were used as reagents for the displacement of decyl methanesulfonate into 1-bromodecane.They were reactive when adsorbed by silica gel.The enhanced activities of the ionenes were hardly dependent on their structures and molecular weights but decreased gradually with increasing the amount of ionene adsorbed by silica gel.Ionene chlorides exhibited a similar enhancement of reactivity when adsorbed by silica gel.However, unlike the ionenes, a large increase in activity due to adsorption was not observed with pendant-type polycations such as poly(4-vinylpyridinium bromide) and poly.The silica gel-supported ionenes also exhibited excellent catalytic activities for solid-liquid-solid triphase substitution reactions, particularly for the reactions between 1-bromodecane and such inorganic salts as consisted of relatively hard-basic nucleophilic anions.
- Ohtani, Noritaka,Chida, Kosaku,Serita, Hajime,Matsunaga, Toshiaki,Kimura, Chikai
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p. 4371 - 4378
(2007/10/02)
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