- Ring Substituent Effects on Acetophenone Dimethyl Acetal Formation. 1. Dual-Parameter Treatment of Equilibrium Data in Methanol, Water, and Dodecane
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For substituted acetophenones, the ketone to acetal equilibrium constants, Kx, measured by a water concentration jump method, are reported.Ketone and acetal partition coefficients, P, for the water-dodecane and methanol-dodecane solvent systems provide Gibbs free energies of transfer from methanol to dodecane and from methanol to water.Both sets of results make it possible to calculate Kx values in water and dodecane; these values are compared with those directly measured in methanol and with equilibrium constants reported for other reactions involving the trigonal to tetrahedral conversion of the carbonyl carbon atom.Substituent effects tor the three solvents are examined by means of the usual dual-parameter Gibbs free energy relationships.The Young-Jencks modified Yukawa-Tsuno equation, log Kx = ρn?n + ρr(?+-?n) + i, gives ρn = 1.73, 1.81, and 0.99 for methanol, dodecane, and water, respectively, but ρr ca. 1 whatever the solvent.It is concluded that the through-ring conjugation effects are solvent independent.In contrast, the Taft-Lewis equation, log Kx = ρI?I + ρ+R?+R + i, gives ρI and ρ+R values that are both solvent dependent.The substituent effects on relative solubilities in methanol, dodecane, and water are examined by means of the equation ΠX(Y) = log PX(Y) - log PH(Y) where Y is the carbonyl or the acetal group and X is the substituent.It is shown that log PX(Y) deviates from additivity (ΠX(Y) ΠX(H) and is Y dependent) because of the effects of X on carbonyl and acetal solvation.These effects are particularly large for solvation of acetals by water molecules.Therefore, substituent effects on Kx are interpreted as being mainly due to (a) an inductive effects of the sustituted ring on ketone stability, (b) a solvent-independent through-ring conjugation effect within the ketone, and (c) a specific inhibition of acetal solvation by water molecules.
- Toullec, Jean,El-Alaoui, Mohiedine,Kleffert, Pascal
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Read Online
- Synthesis and thermal properties of salts comprising cationic bis(oxazoline)-AuIII complexes and fluorinated anions
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Salts comprising cationic bis(oxazoline) (box)-AuIII complexes and fluorinated anions were synthesized and their thermal properties were investigated. Cations that contain box ligands with butyl substituents (butyl-box) were used with either achiral-(R,S) ([1]+) or chiral-(S,S) ([2]+) configurations. [1][Tf2N] (Tf2N- = bis(trifluoromethanesulfonyl)amide) is a solid that can also be classified as an ionic liquid (Tm = 62 °C, Tg = -11 °C). [1]X and [2]X (X = SbF6- and BF4-) exhibit melting points higher than 100 °C, where [1]X exhibits a higher melting point than [2]X. A salt with an ethyl-box ligand ([3][SbF6]) exhibits no melting up to its decomposition temperature of 267 °C. Crystal structure determination revealed that the achiral cation in [1][BF4] has a bent structure. The potential utility of [1][Tf2N] for catalysis was demonstrated by the catalytic formation of an acetal from an alkyne.
- Miura, Yuji,Mochida, Tomoyuki,Motodate, Satoshi,Kato, Keisuke
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Read Online
- Conjugate addition of acetal-derived benzyl radicals generated from low-valent titanium-mediated CO bond cleavage
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A new method for the generation of benzyl radicals from acetals via low-valent titanium-mediated homolytic CO bond cleavage is presented. The low cost and availability of the developed titanium reagent enable efficient access to α-alkoxy carbon radical species via the developed reaction.
- Suga, Takuya,Nakamura, Masaharu,Takada, Ryusei,Ukaji, Yutaka
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supporting information
p. 1258 - 1260
(2021/05/17)
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- P-Anisaldehyde-Photosensitized Sulfonylcyanation of Chiral Cyclobutenes: Enantioselective Access to Cyclic and Acyclic Systems Bearing All-Carbon Quaternary Stereocenters
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The photosensitized p-Anisaldehyde-mediated addition of sulfonylcyanides onto the I -system of cyclobutenes is shown to afford highly functionalized cyclobutanes in high yields and diastereocontrol. The homochiral cyclobutene precursors are accessible on multigram scale in two steps through an asymmetric [2 + 2] cycloaddition/vinyl thioether reduction sequence. The enantiopure cyclobutylnitriles can be elaborated further through SmI2-mediated ring opening or converted into new enantiopure cyclobutenes through base-mediated sulfone elimination.
- Pirenne, Vincent,Traboulsi, Iman,Rouvière, Lisa,Lusseau, Jonathan,Massip, Stéphane,Bassani, Dario M.,Robert, Frédéric,Landais, Yannick
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supporting information
p. 575 - 579
(2020/01/09)
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- Photocatalytic Reductive Formation of α-Tertiary Ethers from Ketals
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A general photocatalytic reductive strategy for the construction of unsymmetrical α-tertiary dialkyl ethers is reported. By merging Lewis acid-mediated ketal activation and visible-light photocatalytic reduction, in situ-generated α-alkoxy radicals were found to engage in addition reactions with a variety of olefinic partners. Good reaction efficiency is demonstrated with a range of ketals of aromatic and aliphatic ketones. Extension to acetal substrates is also described, demonstrating the overall synthetic utility of this methodology for complex ether synthesis.
- Rossolini, Thomas,Ferko, Branislav,Dixon, Darren J.
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supporting information
p. 6668 - 6673
(2019/09/03)
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- Formation of Acetals and Ketals from Carbonyl Compounds: A New and Highly Efficient Method Inspired by Cationic Palladium
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The development of a new, highly efficient, and simple method for masking carbonyl groups as acetals and ketals is described. This methodology relies on the nature of the palladium catalyst to direct the acetalization/ketalization reaction. This new protocol is mild and proceed with a very low catalyst loading at ambient temperatures. The method has been extended to a wide variety of different carbonyl compounds with various steric encumbrances to form the corresponding acetals and ketals in excellent yields.
- Green, Shawn D.,Kindoll, Tyler,Lazaro-Martinez, Brenda,Mensah, Enoch A.,West, Jesse
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p. 1810 - 1814
(2019/09/09)
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- Utilization of hexabromoacetone for protection of alcohols and aldehydes and deprotection of acetals, ketals, and oximes under UV irradiation
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Hexabromoacetone (HBA) was efficiently used for the protection of alcohols and aldehydes and deprotection of benzaldehyde dimethyl acetal, solketal, and other acetals and ketals. In only 10?min, the protection of glycerol yielded 90% of solketal and protection of benzaldehyde gave 95% of benzaldehyde dimethyl acetal. The deprotection of benzaldehyde dimethyl acetal under UV irradiation gave over 90% yield of benzaldehyde within 15?s using only 2.5?mol% of HBA. HBA was also successfully used for deoximation. Solvent was found to play an important role in the efficiency of HBA for these reactions.
- Chaiseeda, Kittichai,Chantharadet, Ladawan,Chavasiri, Warinthorn
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p. 1305 - 1323
(2017/10/30)
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- Hierarchical porous organic polymer as an efficient metal-free catalyst for acetalization of carbonyl compounds with alcohols
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An efficient melamine-porous organic polymer (M-POP) as N-functionalized organic polymer catalyst was synthesized with melamine and terephthalaldehyde by a facile microwave-assisted method. The synthesized M-POP exhibited a high specific surface area with hierarchical pore structure of both mesoporosity and microporosity. The rich N-moieties namely, C[dbnd]N and N–H from the melamine precursor were found to show hydrogen-bonding ability with various organic molecules such as carbonyl compounds. This was illustrated in the acetalization of aldehydes and ketones with methanol or ethylene glycol under mild conditions as a metal-free H-bonding catalyst with high product selectivity. The superior catalytic performance of M-POP was attributed to the availability of a large number of H-bonding sites both as H-donor and H-acceptor between the reactants and the catalyst.
- Kim, Joong-Jo,Lim, Cheang-Rae,Reddy, Benjaram M.,Park, Sang-Eon
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- Silver-Catalyzed Olefination of Acetals and Ketals with Diazoesters to β-Alkoxyacrylates
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The first silver-catalyzed reaction of acetals or ketals with diazoesters leading to trisubstituted or tetrasubstituted β-alkoxyacrylates is now reported. A broad range of acetals and ketals bearing different substituents is compatible with this protocol and thus provides an attractive approach for the synthesis of complex β-alkoxyacrylates. The power of this method was further demonstrated by the successful synthesis of picoxystrobin, which is one of the most popular agricultural fungicides commercialized by Dupont.
- Li, Jiawen,Qian, Bo,Huang, Hanmin
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supporting information
p. 7090 - 7094
(2018/11/23)
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- A fluorinated cobalt(III) porphyrin complex for hydroalkoxylation of alkynes
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A fluorinated cobalt(III) porphyrin complex [Co(TPFPP)-NTf2·2C2H5OH, where TPFPP=5,10,15,20-tetrakis(penta-fluorophenyl)porphyrin, Tf=CF3SO2] promotes hydroalkoxylation of alkynes to give acetals in good to excellent yields. The acetals can be directly functionalized with nucleophiles in a one-pot procedure.
- Ushimaru, Richiro,Nishimura, Takuho,Iwatsuki, Toshiki,Naka, Hiroshi
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p. 1000 - 1003
(2017/11/17)
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- In situ formed acetals facilitated direct Michael addition of unactivated ketones
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TfOH-promoted synthesis of 1,5-diketones by the Michael reaction of unactivated ketones with chalcones has been described. Acetals formed under HC(OMe)3/TfOH conditions generate the required enol-equivalents for a smooth Michael reaction. A wide array of symmetrical and unsymmetrical 1,5-diketones has been synthesised.
- Koppolu, Srinivasa Rao,Balamurugan, Rengarajan
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supporting information
p. 1186 - 1192
(2017/02/10)
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- Dual-gold(I)-generated trifluoromethylation of terminal alkynes with Togni's reagent
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The interaction of a Au(I) catalyst (JohnPhosAu(I)-MeCN/SbF6) and the Togni's reagent 1, as a source of electrophilic trifluoromethyl group, has been studied in order to develop gold-catalysed alkyne trifluoromethylation reactions. Alkyne-CF3products were prepared in moderate yields (up to 46%) by electrophilic trifluoromethylation of terminal arylalkynes with Togni's reagent 1 in the presence of sub-stoichiometric amounts of gold catalyst (25%). The proposed addition-elimination reaction mechanism proceeds through a Au-Togni Reagent complex with a linear Togni Reagent-O-Au(I)-P-(phosphane) coordination mode (X-ray analysis). Alkyne deprotonation gives rapid formation of protonated Togni Reagent and a σ,π-acetylide dual-Au complex, confirmed by X-ray analysis. It was shown that the σ,π-dual-Au complex activates for trifluoromethylation, most likely by transfer of a [LAu]+fragment to the alkyne substrate. The resulting reactive π-Au+-alkyne intermediate probably undergoes O-/CF3-addition of Togni Reagent, and final elimination of Togni alcohol gives the alkyne-CF3product.
- Siah, Huey-San Melanie,Fiksdahl, Anne
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supporting information
p. 24 - 33
(2017/03/10)
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- Graphitic carbon nitride catalysed photoacetalization of aldehydes/ketones under ambient conditions
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Graphitic-C3N4 is shown for the first time to catalyse photoacetalization of aldehydes/ketones with alcohols to acetals in high yields using visible light under ambient conditions; transient charge separation over the material is effective to catalyse the reaction in the absence of Lewis or Br?nsted acids, giving a new green alternative catalyst.
- Abdullah Khan,Teixeira, Ivo F.,Li, Molly M. J.,Koito, Yusuke,Tsang, Shik Chi Edman
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supporting information
p. 2772 - 2775
(2016/02/18)
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- Convergent synthesis and cytotoxicity of novel trifluoromethyl-substituted (1H-pyrazol-1-yl)(quinolin-4-yl) methanones
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A convergent synthesis of a series of 16 new polysubstituted (5-hydroxy-5-(trifluoromethyl)-4,5-dihydro-1H-pyrazol-1-yl)(quinolin-4-yl)methanones, starting from isatin and alky(aryl/heteroaryl) ketones, is described. The diheteroaryl methanones were achieved at yields of up to 95% by a [3?+?2] cyclocondensation reaction involving 4-alkyl(aryl/heteroaryl)-4-methoxy-1,1,1-trifluorobut-3-en-2-ones (by two-step reaction) and 2-alkyl(aryl/heteroaryl)-4-carbohydrazides (by three-step reaction). Subsequently, representative dehydrated heterocyclic derivatives were obtained from the respective 5-hydroxy-2-pyrazoline moieties by classical dehydration reactions, which resulted in the corresponding (5-(trifluoromethyl)-1H-pyrazol-1-yl)(quinolin-4-yl)methanones (three examples) at yields of 69–82%. The subsequent cytotoxicity evaluation showed that compounds with aromatic groups at the 2-position of the quinoline and a methyl moiety at the 3-position of the pyrazole have significant cytotoxicity in human leukocytes at high concentrations (200?μM).
- Bonacorso, Helio G.,Nogara, Pablo A.,Silva, Fernanda D'A.,Rosa, Wilian C.,Wiethan, Carson W.,Zanatta, Nilo,Martins, Marcos A.P.,Rocha, Jo?o B.T.
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- Eco-friendly synthesis and antioxidant activity of new trifluoromethyl-substituted N-(pyrimidin-2-yl)benzo[d]thiazol-2-amines and some N-derivatives
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Abstract: A convenient and environmentally benign procedure for the synthesis of a new series of trifluoromethyl-substituted N-(pyrimidin-2-yl)benzo[d]thiazol-2-amines by the cyclocondensation reaction of (benzo[d]thiazolyl)guanidine with either 4-alkoxy-4-alkyl(aryl/heteroaryl)-1,1,1-trifluoroalk-3-en-2-ones or 2,2,2-trifluoro-1-(2-methoxycyclohexen-1-en-1-yl)ethanone is described. The main reactions were performed in refluxing water as the solvent (8–24?h), without catalysts, and the corresponding new N-(pyrimidinyl)-1H-(benzo[d]thiazolyl)amines were obtained at a 60–88?% yield. Subsequently, some di(hetero)arylamines were derivatized to the respective tertiary amines via easy N-alkylation and N-alkenylation reactions at 55–82?% yields. Finally, the Lipinski parameters and the total antioxidant activity of the new series of secondary arylamines were also evaluated. Graphical abstract: [Figure not available: see fulltext.]
- Bonacorso, Helio G.,Calheiro, Tainara P.,Rodrigues, Melissa B.,Stefanello, Sílvio T.,Soares, Félix A. A.,Zanatta, Nilo,Martins, Marcos A. P.
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p. 2185 - 2194
(2016/11/17)
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- A structure/catalytic activity study of gold(i)-NHC complexes, as well as their recyclability and reusability, in the hydration of alkynes in aqueous medium
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We conducted a structure/catalytic activity study of water-soluble gold(i) complexes-supporting sulfonated NHC ligands-in the hydration of alkynes in pure water or water nsp;:nsp;methanol (1nsp;:nsp;1), as well as their recyclability. Comparative studies were carried out with the addition of different silver salts. Our results indicate that the bulkier complex is the most effective and that the addition of methanol as co-solvent not only shortens reaction times but also stabilizes the less bulky complexes.
- Fernández, Gabriela A.,Chopa, Alicia B.,Silbestri, Gustavo F.
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p. 1921 - 1929
(2016/04/05)
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- Highly efficient acetalization of carbonyl compounds catalyzed by anilin-aldehyde resin salts
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A mild procedures for the syntheses of ethylene acetals and dimethyl acetals from the corresponding aldehydes and ketones catalyzed by 1mol% of anilinealdehyde resin salts are described. This method is also useful for the synthesis of dimethyl acetals of diaryl ketones.
- Tanemura, Kiyoshi,Suzuki, Tsuneo
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supporting information
p. 797 - 799
(2015/06/22)
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- Efficient syntheses of ethyl 2-methylthio-and ethyl 2-benzylthio-6-methyl(aryl)pyrimidine-4-carboxylates and their carboxylic acid derivatives
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A simple and efficient procedure for the synthesis of ethyl 2-methylthio-and ethyl 2-benzylthio-6-methyl(aryl)-pyrimidine-4-carboxylates and their corresponding acid derivatives is reported. The products are obtained in good yields via the cyclocondensation reaction of ethyl 4-alkoxy-2-oxo-4-methyl(aryl)-but-3-enoates with 2-methylisothiourea sulfate or 2-benzylisothiourea hydrochloride, under mild, basic, aqueous conditions.
- Zanatta, Nilo,Fortes, Andressa S.,Bencke, Carlos E.,Marangoni, Mário A.,Camargo, Adriano F.,Fantinel, Cassio A.,Bonacorso, Helio G.,Martins, Marcos A. P.
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p. 827 - 835
(2015/03/14)
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- Hydration of terminal alkynes catalyzed by water-soluble cobalt porphyrin complexes
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Water-soluble cobalt(III) porphyrin complexes were found to promote the hydration of terminal alkynes to give methyl ketones. The alkyne hydration proceeded in good to excellent yield with 0.1 to 2 mol % cobalt catalyst 1 and was compatible with the presence of acid/base- or redox-sensitive functional groups such as alkyl silyl ethers; allyl ethers; trityl ethers; benzyl ethers; carboxylic esters; boronic esters; carboxamides; nitriles; and nitro, iodo, and acetal groups. Some of the alkyne substrates tested here are otherwise difficult to hydrate. The alkyne hydration can be performed on a gram scale, and the catalyst can be recovered by aqueous workup.
- Tachinami, Tadashi,Nishimura, Takuho,Ushimaru, Richiro,Noyori, Ryoji,Naka, Hiroshi
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supporting information
p. 50 - 53
(2013/02/23)
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- Divergent Diels-Alder methodology from methyl coumalate toward functionalized aromatics
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An inverse electron-demand Diels-Alder reaction between methyl coumalate and electron-rich dienophiles produces substituted benzoates. A high-yielding, single-pot procedure transforms readily accessible vinyl ether, ketal, or orthoester dienophiles into functionalized aromatic systems in a versatile route.
- Lee, Jennifer J.,Kraus, George A.
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supporting information
p. 2366 - 2368
(2013/06/26)
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- Anodic cleavage of several ketone N-phenylsemicarbazones into methyl N-phenylcarbamate and the corresponding dimethyl acetals
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Several ketone N-phenylsemicarbazones were electrooxidized in the presence of potassium iodide and a base using methanol as the solvent to give nearly commensurate amounts of methyl N-phenylcarbamate and the corresponding dimethyl acetals. Continuous evolution of gaseous nitrogen was observed from the anolyte during the electrooxidation. The reactions were carried out under very mild reaction conditions and are presumed to proceed through a four-electron oxidation process, in which the iodide ion plays an important role as an electron carrier.
- Nishikawa, Shinnosuke,Yamamori, Haruki,Ohashi, Kousuke,Okimoto, Mitsuhiro,Hoshi, Masayuki,Yoshida, Takashi
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p. 1766 - 1771
(2013/05/21)
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- Copper(II) cubane complexes built from electro- and photosensitive β-aminovinyl trifluoromethyl ketone ligands
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A new family of [Cu4L4] cubane complexes have been synthesized by the self-assembly of CuII salts and β-aminovinyl trifluoromethyl ketone ligands. The resulting polynuclear architectures were especially designed to exhibit magnetic properties arising from the metallic cubane architecture as well as electro- or photosensitive properties arising from the ligands. The optical and electrochemical behaviours of the compounds were measured in solution to confirm that the properties of the free ligands were retained within the elaborated complexes. DFT investigations of the organic moieties were conducted with the aim of assigning the observed electronic processes to the different redox steps and absorption bands. The crystal structures of the polynuclear complexes were solved and refined by single-crystal X-ray diffraction analysis and correlated to variable-temperature magnetic susceptibility data. The overall expected ferromagnetic behaviour of the [Cu4L4] complexes is weakly influenced by the ligand substitutions. Ab initio configuration interaction calculations helped us to detail the variations of the various magnetic exchange pathways.
- Chopin, Nicolas,Medebielle, Maurice,Chastanet, Guillaume,Le Guennic, Boris,Pilet, Guillaume
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p. 5058 - 5070,13
(2020/09/16)
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- Bis(perfluorooctanesulfonyl)imide supported on fluorous silica gel: Application to protection of carbonyls
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The immobilization of bis(perfluorooctanesulfonyl)imide (HNPf2) on fluorous silica gel (FSG) and its utilization in protection of carbonyls have been investigated. This system is reasonably general and can be applied to converting several carbonyls to the corresponding acetals and ketals in good to excellent yields. There is no need for the use of anhydrous solvents or inert atmosphere. Recycling studies have shown that the FSG-supported HNPf2 catalyst can be readily recovered and reused several times without significant loss of activity.
- Hong, Mei,Xiao, Guomin
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experimental part
p. 121 - 126
(2012/08/28)
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- Conjugation chemistry through acetals toward a dextran-based delivery system for controlled release of siRNA
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New conjugation chemistry for polysaccharides, exemplified by dextran, was developed to enable the attachment of therapeutic or other functional moieties to the polysaccharide through cleavable acetal linkages. The acid-lability of the acetal groups allows the release of therapeutics under acidic conditions, such as that of the endocytic compartments of cells, regenerating the original free polysaccharide in the end. The physical and chemical behavior of these acetal groups can be adjusted by modifying their stereoelectronic and steric properties, thereby providing materials with tunable degradation and release rates. We have applied this conjugation chemistry in the development of water-soluble siRNA carriers, namely acetal-linked amino-dextrans, with various amine structures attached through either slow- or fast-degrading acetal linker. The carriers with the best combination of amine moieties and structural composition of acetals showed high in vitro transfection efficiency and low cytotoxicity in the delivery of siRNA.
- Cui, Lina,Cohen, Jessica L.,Chu, Crystal K.,Wich, Peter R.,Kierstead, Paul H.,Frechet, Jean M. J.
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p. 15840 - 15848,9
(2020/08/24)
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- An efficient photoinduced deprotection of aromatic acetals and ketals
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A novel type of photodeprotection reaction of simple aromatic acetals and ketals is described. The deprotection is highly efficient under optimized conditions. The aromatic ring confers the photoreactivity to the compounds. The efficiency of the process depends on the structure of the acetal moiety. The common minor side reaction, the photooxidation, becomes the major reaction pathway in the cases of cyclic acetals. The use of photon as only reagent makes this procedure especially attractive for acetal deprotection.
- Thevenet, Damien,Neier, Reinhard
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experimental part
p. 331 - 346
(2011/04/22)
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- ClickEnam. 1. Synthesis of novel 1,4-disubsituted-[1,2,3]-triazole-derived β-aminovinyl trifluoromethylated ketones and their copper(II) complexes
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The copper(I) catalyzed cycloaddition reaction of N-Boc propargyl amine (dipolarophile) 1 with benzyl azide (1,3-dipole) 2 was found to proceed smoothly in t-BuOH/H2O at room temperature, to furnish the corresponding 1,4-disubstituted-[1,2,3]-triazole-derived N-Boc amine 3 in good yield. Deprotection of 3 with trifluoroacetic acid and addition of the trifluoroacetate salt 4 in the presence of triethylamine, with a series of methoxyvinyl(trifluoromethyl)ketones 10-14, gave the corresponding β-aminovinyl trifluoromethylated ketones 15-19 in moderate to good yields. Two copper(II) complexes, one monomer and one dimer with chlorine double bridge, 20 and 21, respectively, were also prepared and their crystal structure determined. β-Aminovinyl trifluoromethylated ketones 15-17 and complexes 20 and 21 have been screened as potential antifungal agents and the antimalarial activity of 15 and 16 were tested against two Plasmodium falciparum strains (3D7 and W2).
- Chopin, Nicolas,Decamps, Sophie,Gouger, Aude,Médebielle, Maurice,Picot, Stéphane,Bienvenu, Anne-Lise,Pilet, Guillaume
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experimental part
p. 850 - 857
(2011/10/04)
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- Mesoporous sulfated zirconia mediated acetalization reactions
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A novel, convenient, one step synthetic procedure for the synthesis of mesoporous sulfated zirconia (m-SZ) using zirconium carbonate complex and its use as solid acid catalyst for the acetalization of different carbonyl compound is reported. The high specific BET surface area (234 m2 g -1) of m-SZ is achieved after the removal of the surfactant (cetyltrymethylammonium bromide, CTAB) through calcination at 550 °C for 6 h. Microscopic analysis indicated the presence of spherical particles with worm like pores. DRIFT (diffuse reflectance FTIR) of pyridine adsorbed m-SZ and NH3-TPD (temperature programmed desorption) analysis suggested the presence of appreciable amount of Bro?nsted acid sites. The synthesized m-SZ showed high catalytic activity towards protection of carbonyl compounds through acetal/ketal formation. For the open ketal (from cyclohexanone and methanol) 97% conversion with 100% selectivity was obtained in 1 h at room temperature under solvent free condition. The catalyst can be easily recycled after separation from the reaction system without considerable loss in catalytic activity.
- Sinhamahapatra, Apurba,Sutradhar, Narottom,Ghosh, Malay,Bajaj, Hari C.,Panda, Asit B.
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experimental part
p. 87 - 93
(2012/04/10)
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- Metal organic frameworks as solid acid catalysts for acetalization of aldehydes with methanol
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Room temperature acetalization of aldehydes with methanol has been carried out using metal organic frameworks (MOFs) as solid heterogeneous catalysts. Of the MOFs tested, a copper-containing MOF [Cu3(BTC)2] (BTC=1,3,5-benzenetricarboxylate) showed better catalytic activity than an iron-containing MOF [Fe(BTC)] and an aluminium containing MOF [Al 2(BDC)3] (BDC=1,4-benzenedicarboxylate). The protocol was validated for a series of aromatic and aliphatic aldehydes and used to protect various aldehydes into commercially important acetals in good yields without the need of water removal. In addition, the reusability and heterogeneity of this catalytic system was demonstrated. The structural stability of MOF was further studied by characterization with powder X-ray diffraction, Brunauer-Emmett- Teller surface area measurements and Fourier-transformed infrared spectroscopic analysis of a deactivated catalyst used to convert a large amount of benzaldehyde. The performance of copper MOF as acetalization catalyst compares favourably with those of other conventional homogeneous and heterogeneous catalysts such as zinc chloride, zeolite and clay. Copyright
- Dhakshinamoorthy, Amarajothi,Alvaro, Mercedes,Garcia, Hermenegildo
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scheme or table
p. 3022 - 3030
(2011/02/24)
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- The use of anhydrous CeCl3 as a recyclable and selective catalyst for the acetalization of aldehydes and ketones
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An efficient, clean, chemoselective and solvent-free method for the synthesis of ketone and aldehyde dimethyl acetals was developed using trimethyl orthoformate and commercially available anhydrous CeCl3 as a recyclable catalyst. The method is general and affords the protected carbonyl compounds in good yields and under mild conditions, including aryl and alkyl ketones and activated aldehydes. The catalyst could be utilised directly for 3 cycles, without significant loss of activity.
- Silveira, Claudio C.,Mendes, Samuel R.,Ziembowicz, Francieli I.,Lenarda?o, Eder J.,Perin, Gelson
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scheme or table
p. 371 - 374
(2010/09/07)
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- A facile procedure for acetalization of aldehydes and ketones catalyzed by cerium(III) trifluoromethanesulfonate
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Aldehydes and ketones are readily protected in the presence of trialkyl orthoformate and a catalytic amount of cerium(III) trifluoromethanesulfonate under mild conditions to give the corresponding acetals in good to excellent yields. Due to the mild reaction conditions, this method is compatible with acid-sensitive substrates. Copyright
- Ono, Fumiaki,Inatomi, Yoshiko,Tada, Yuusuke,Mori, Masaki,Sato, Tsuneo
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experimental part
p. 96 - 97
(2009/11/30)
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- A novel approach to the practical synthesis of sulfides: An InBr 3-Et3SiH catalytic system promoted the direct reductive sulfidation of acetais with disulfides
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We have demonstrated a facile and direct synthesis of sulfide derivatives using acetais and ketals, derived, from aromatic/ conjugated, aldehydes and aromatic ketones, with disulfides and the InBr3-Et3SiH reducing system., We also succeeded in developing an unprecedented one-pot preparation of an aliphatic sulfide from a disulfide and an aliphatic acetal. (Wiley-VCH Verlag GmbH & Co. KGaA.
- Sakai, Norio,Moritaka, Kohei,Konakahara, Takeo
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supporting information; experimental part
p. 4123 - 4127
(2009/12/09)
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- Zinc chloride as an efficient catalyst for chemoselective dimethyl acetalization
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Commercially available anhydrous zinc chloride has been found to be a highly efficient catalyst for dimethyl acetalization in high yields by treatment of aldehydes and ketones with trimethyl orthoformate in methanol-cyclohexane at reflux temperature. Copyright Taylor & Francis Group, LLC.
- Roy, Anupam,Rahman, Matiur,Das, Sudarshan,Kundu, Dhiman,Kundu, Shrishnu Kumar,Majee, Adinath,Hajra, Alakananda
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experimental part
p. 590 - 595
(2009/07/04)
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- Iron(III) tosylate in the preparation of dimethyl and diethyl acetals from ketones and β-keto enol ethers from cyclic β-diketones
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An efficient method for conversion of ketones to their corresponding dimethyl and diethyl acetals and of cyclic β-diketones into β-keto enol ethers using Fe(OTs)3 as a catalyst is described. Copyright Taylor & Francis Group, LLC.
- Mansilla, Horacio,Afonso, Maria M.
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p. 2607 - 2618
(2008/12/22)
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- Indium(III)trifluoromethanesulfonate as a mild, efficient catalyst for the formation of acetals and ketals in the presence of acid sensitive functional groups
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Aldehydes and ketones, including acetophenone and benzophenone, are readily protected under mild, neutral conditions in the presence of various alcohols or orthoformates and catalytic amounts of indium(III) trifluoromethanesulfonate (0.8 mol %) under either room temperature or mild heating conditions to give the corresponding cyclic and acyclic acetals and ketals in good to excellent yields. Acid sensitive functional groups, N-Boc, THP, and TBDMS do not undergo competitive deprotection under the reported conditions.
- Gregg, Brian T.,Golden, Kathryn C.,Quinn, John F.
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p. 3287 - 3295
(2008/09/21)
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- Tetrafluoroboric acid adsorbed on silica gel as a reusable heterogeneous dual-purpose catalyst for conversion of aldehydes/ketones into acetals/ketals and back again
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Aldehydes and ketones can be protected as acetals and ketals by treatment with trimethyl orthoformate (TMOF) or triethyl orthoformate (TEOF) under the catalytic influence of tetrafluoroboric acid adsorbed on silica gel (HBF 4-SiO2). In the case of aldehydes or ketones with highly electrophilic carbonyl group, the reactions are carried out under solvent-free conditions. Aryl alkyl ketones, aryl styryl ketones, aldehydes with weakly electrophilic carbonyl groups, and aldehydes with substituents that can coordinate with the catalyst require the presence of the corresponding alcohol as solvent. For substrates that can be converted into acetals under neat conditions, the acetal formation takes place at a faster rate when the alcohol is used as the solvent. The catalyst can be recovered and reused/recycled four times (after reactivation after each use) without any significant decrease in its catalytic efficiency. The parent aldehydes/ketones are regenerated from the corresponding acetals/ketals in high yields by the treatment with water-alcohol in the presence of HBF4-SiO2 at room temperature for short times. Excellent selectivity was observed during inter- and intramolecular competition studies involving carbonyl substrates with varying electronic and steric environments. Selective acetal formation of benzaldehyde takes place in the presence of 4-(dimethylamino)benzaldehyde, thiophene-2-carboxaldehyde, 1-naphthaldehyde, 9-anthraldehyde, or acetophenone, but 3-nitrobenzaldehyde undergoes selective acetal formation in preference to benzaldehyde. In the case of 4-acetylbenzaldehyde, exclusive acetal formation of the aldehyde carbonyl group occurs. Georg Thieme Verlag Stuttgart.
- Kumar, Dinesh,Kumar, Raj,Chakraborti, Asit K.
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p. 1249 - 1256
(2008/12/22)
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- A marcus treatment of rate constants for protonation of ring-substituted α-methoxystyrenes: Intrinsic reaction barriers and the shape of the reaction coordinate
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Rate and equilibrium constants were determined for protonation of ring-substituted α-methoxystyrenes by hydronium ion and by carboxylic acids to form the corresponding ring-substituted α-methyl α-methoxybenzyl carbocations at 25°C and I = 1.0 (KCl). The thermodynamic barrier to carbocation formation increases by 14.5 kcal/mol as the phenyl ring substituent(s) is changed from 4-MeO- to 3,5-di-NO2-, and as the carboxylic acid is changed from dichloroacetic to acetic acid. The Bronsted coefficient a for protonation by carboxylic acids increases from 0.67 to 0.77 over this range of phenyl ring substituents, and the Bronsted coefficient β for proton transfer increases from 0.63 to 0.69 as the carboxylic acid is changed from dichloroacetic to acetic acid. The change in these Bronsted coefficients with changing reaction driving force, ?α/?ΔG°av = ?β/ ?ΔG°av = 1/8Λ = 0.011, is used to calculate a Marcus intrinsic reaction barrier of Λ = 11 kcal/mol which is close to the barrier of 13 kcal/mol for thermoneutral proton transfer between this series of acids and bases. The value of α = 0.66 for thermoneutral proton transfer is greater than α = 0.50 required by a reaction that follows the Marcus equation. This elevated value of β may be due to an asymmetry in the reaction coordinate that arises from the difference in the intrinsic barriers for proton transfer at the oxygen acid reactant and resonance-stabilized carbon acid product.
- Richard, John P.,Williams, Kathleen B.
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p. 6952 - 6961
(2008/02/09)
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- Perchloric acid adsorbed on silica gel (HClO4-SiO2) as an inexpensive, extremely efficient, and reusable dual catalyst system for acetal/ketal formation and their deprotection to aldehydes/ketones
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Perchloric acid adsorbed on silica gel (HClO4-SiO2) is reported as extremely efficient, inexpensive, and reusable catalyst for dual role for protection of aldehydes/ketones (with trialkyl orthoformates) as acetals/ketals and deprotection (with water-alcohol) to regenerate the carbonyl compounds in high yields at room temperature and in short times. Acetalization/ketalization of electrophilic aldehydes/ketones was carried out under solvent-free conditions. Weakly electrophilic aldehydes/ketones and aldehydes having a substituent that can coordinate with the catalyst, required the corresponding alcohol as solvent. Georg Thieme Verlag Stuttgart.
- Kumar, Raj,Kumar, Dinesh,Chakraborti, Asit K.
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p. 299 - 303
(2007/10/03)
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- Reductive coupling of aromatic dialkyl acetals using the combination of zinc and chlorotrimethylsilane in the presence of potassium carbonate
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The treatment of aromatic acetals with zinc and chlorosilane in the presence of potassium carbonate in toluene brought about facile and effective reductive coupling to give the corresponding coupling products. Copyright
- Hatano, Bunpei,Nagahashi, Keita,Habaue, Shigeki
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p. 1418 - 1419
(2008/03/14)
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- Iridium complex-catalyzed addition of water and alcohols to non-activated terminal alkynes
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The addition of water and alcohols to non-activated terminal alkynes was found to be promoted by an iridium complex combined with Lewis acid and phosphite. Thus, terminal alkynes reacted with water or alcohols to give ketones or ketals, respectively, in good to excellent yields. α,ω-Diyne like 1,7-octadiyne was converted into 1-(2-methyl-cyclopent-1-enyl)ethanone through the intramoleculer aldol condensation of the resulting 2,7-octanedione induced by Lewis acid.
- Hirabayashi, Tomotaka,Okimoto, Yoshio,Saito, Akiyo,Morita, Masao,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 2231 - 2234
(2007/10/03)
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- Simple method for the preparation of dimethyl acetals from ketones with montmorillonite K 10 and p-toluenesulfonic acid
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A simple method for conversion of ketones to their corresponding dimethyl acetals using montmorillonite K 10 and p-toluenesulfonic acid as acidic cocatalysts under very mild reaction conditions is described. Copyright Taylor & Francis Group, LLC.
- Mansilla, Horacio,Regas, David
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p. 2195 - 2201
(2007/10/03)
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- Reductive cleavage of acetals and ketals with 9-borabicyclo[3.3.1]nonane
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The reductive cleavage of benzaldehyde acetals and acetophenone ketals with the air-stable crystalline 9-borabicyclo[3.3.1]-nonane dimer provides monobenzylated ether derivatives of diols and 1,2-oxygen-transposed β-phenethyl alcohols, respectively. The boron moiety is effectively recovered through simple procedures which involve convenient air-stable reagents and boron byproducts. The process is particularly selective for 1,3-diols giving the more substituted monobenzyl ether derivatives exclusively. With acetophenone ketals both reduction and elimination occur, permitting 9-BBN-H to hydroborate the resulting styrene to produce 1,2-oxygen-transposed β-phenethyl alcohols cleanly. Potential applications of this new process were illustrated with the synthesis of the hallucinogen, mescaline, and the analgesic, ibufenac.
- Soderquist, John A.,Kock, Iveliz,Estrella, Maria E.
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supporting information
p. 1076 - 1079
(2012/12/23)
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- Antimalarial activity of 4-(5-trifluoromethyl-1H-pyrazol-1-yl)-chloroquine analogues
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The antimalarial activity of chloroquine-pyrazole analogues, synthesized from the reaction of 1,1,1-trifluoro-4-methoxy-3-alken-2-ones with 4-hydrazino-7-chloroquinoline, has been evaluated in vitro against a chloroquine resistant Plasmodium falciparum clone. Parasite growth in the presence of the test drugs was measured by incorporation of [3H]hypoxanthine in comparison to controls with no drugs. All but one of the eight (4,5-dihydropyrazol-1-yl) chloroquine 2 derivatives tested showed a significant activity in vitro, thus, are a promising new class of antimalarials. The three most active ones were also tested in vivo against Plasmodium berghei in mice. However, the (pyrazol-1-yl) chloroquine 3 derivatives were mostly inactive, suggesting that the aromatic functionality of the pyrazole ring was critical.
- Cunico, Wilson,Cechinel, Cleber A.,Bonacorso, Helio G.,Martins, Marcos A. P.,Zanatta, Nilo,De Souza, Marcus V.N.,Freitas, Isabela O.,Soares, Rodrigo P. P.,Krettli, Antoniana U.
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p. 649 - 653
(2007/10/03)
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- Pd(II)-catalyzed conversion of styrene derivatives to acetals: Impact of (-)-sparteine on regioselectivity
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Pd[(-)-sparteine]Cl2 catalyzes the formation of dialkyl acetals from styrene derivatives with Markovnikov regioselectivity. The substrate scope of this reaction has been investigated, and initial mechanistic studies indicate that the reaction proceeds through an enol ether intermediate and a Pd-hydride.
- Balija, Amy M.,Stowers, Kara J.,Schultz, Mitchell J.,Sigman, Matthew S.
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p. 1121 - 1124
(2007/10/03)
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- High-pressure-promoted uncatalyzed ketalization of ketones and oxy-Michael/ketalization of conjugated enones
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A new practical method for ketalization or oxy-Michael/ketalization was developed using the high-pressure-promoted condensation of ketones or α,β-unsaturated ketones with alcohols in the presence of trialkyl orthoformates as water scavengers. Georg Thieme Verlag Stuttgart.
- Kumamoto, Koji,Ichikawa, Yoshiyasu,Kotsuki, Hiyoshizo
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p. 2254 - 2256
(2007/10/03)
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- Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for acetal formation
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Commercially available copper(II) tetrafluoroborate hydrate has been found to be a highly efficient catalyst for dimethyl/diethyl acetal formation in high yields from aldehydes and ketones by reaction with trimethyl/triethyl orthoformate at room temperature and in short period. Acetalisation was carried out under solvent-free conditions with electrophilic aldehydes/ketones. For weakly electrophilic aldehydes/ketones (e.g., benzaldehyde, cinnamaldehyde and acetophenone) and for aldehydes having a substituent that can coordinate with the catalyst, the corresponding alcohol was used as solvent.
- Kumar, Raj,Chakraborti, Asit K.
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p. 8319 - 8323
(2007/10/03)
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- Cobalt(II)-catalyzed chemoselective synthesis of acetals from aldehydes
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The acetalization of aldehydes has been studied with methanol, ethanol, and 2-propanol using CoCl2 in high yields under reflux conditions. The reaction is simple, efficient, chemoselective and does not involve any other additive.
- Velusamy, Subbarayan,Punniyamurthy
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p. 4917 - 4920
(2007/10/03)
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- An efficient and versatile procedure for the synthesis of acetals from aldehydes and ketones catalyzed by lithium tetrafluoroborate
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Acetals are obtained in good to excellent yields by treatment of aldehydes and ketones with trialkyl orthoformate and the corresponding alcohol in the presence of a catalytic amount of lithium tetrafluoroborate. Due to the mild reaction conditions, this method is compatible with acid-sensitive substrates.
- Hamada, Nao,Kazahaya, Kiyoshi,Shimizu, Hisashi,Sato, Tsuneo
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p. 1074 - 1076
(2015/10/07)
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- Organometallic gold(III) compounds as catalysts for the addition of water and methanol to terminal alkynes
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Different inorganic and organometallic gold(III) and gold(I) complexes have been tested in the addition of water and methanol to terminal alkynes. Anionic and neutral organometallic gold(III) compounds can efficiently mediate these reactions in neutral media in refluxing methanol. The compounds are added in catalytic amounts (1.6-4.5 mol% with respect to the alkyne), Thus, compounds of the general formula Q[AuRCl3], Q[AuR2Cl2], [AuRCl2]2, and [AuR2Cl]2, (Q = BzPPh3+, PPN: N(PPh3)2+ or N(Bu)4+; R = C6F5 or 2,4,6-(CH3)3C6H2) seem to behave as Lewis acids in nucleophilic additions to triple bonds. Some intermediates could be detected in the stoichiometric reaction between [Au(C6F 5)2Cl]2 and phenylacetylene that was followed by variable temperature 1H, 19F{1H}, COSY 19F{1H}-19F{1H}, and 2H{1H} NMR experiments. Compound [Au(C6F 5)2Cl]2 is also able to catalyze the hydration of phenylacetylene at room temperature. A plausible mechanism for the hydration reaction has been proposed.
- Casado, Raquel,Contel, Maria,Laguna, Mariano,Romero, Pilar,Sanz, Sergio
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p. 11925 - 11935
(2007/10/03)
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- An efficient protection of carbonyls and deprotection of acetals using decaborane
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Carbonyls were efficiently converted to the corresponding dimethyl acetals at room temperature using trimethyl orthoformate and 1 mol% of decaborane under a nitrogen atmosphere. In turn, acetals were deprotected to the corresponding carbonyls using 1 mol% of decaborane in aqueous THF chemoselectively.
- Lee, Seung Hwan,Lee, Ji Hee,Yoon, Cheol Min
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p. 2699 - 2703
(2015/10/07)
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- Tetrabutylammonium tribromide (TBATB) as an efficient generator of HBr for an efficient chemoselective reagent for acetalization of carbonyl compounds
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Acyclic and cyclic acetals of various carbonyl compounds were obtained in excellent yields under a mild reaction condition in the presence of trialkyl orthoformate and a catalytic amount of tetrabutylammonium tribromide (TBATB) in absolute alcohol. Chemoselective acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, shorter reaction times, mild reaction conditions, the stability of acid-sensitive protecting groups, high efficiencies, facile isolation of the desired products, and the catalytic nature of the reagent make the present methodology a practical alternative.
- Gopinath, Rangam,Haque, Sk. Jiaul,Patel, Bhisma K.
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p. 5842 - 5845
(2007/10/03)
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