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Very Short Reaction Times (very + short_reaction_time)
Selected AbstractsHighly efficient and chemoselective acetalization of carbonyl compounds catalyzed by new and reusable zirconyl triflate, ZrO(OTf)2HETEROATOM CHEMISTRY, Issue 3 2009Majid Moghadam Various types of aromatic aldehydes were efficiently converted to their corresponding 1,3-dioxanes and 1,3-dioxolane with 1,3-propanediol and ethylene glycol, respectively, in the presence of catalytic amount of ZrO(OTf)2 in acetonitrile at room temperature. The catalyst can be reused several times without loss of its catalytic activity. Very short reaction times, selective acetalization of aromatic aldehydes in the presence of aliphatic aldehydes and ketones, very mild reaction conditions, reusability of the catalyst, and easy workup are noteworthy advantages of this method. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:131,135, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20523 [source] Organocatalytic synthesis of cyanohydrin trimethylsilyl ethers by potassium 4-benzylpiperidinedithiocarbamate under solvent-free conditionsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010Mohammad G. Dekamin Abstract Potassium 4-benzylpiperidinedithiocarbamate was found to be an efficient organocatalyst for facile addition of trimethylsilyl cyanide to a wide variety of aldehydes and ketones to afford corresponding cyanohydrin trimethylsilyl ethers in high to quantitative yields. The reaction proceeded smoothly by employing 2.0 mol% PBPDC loading under mild conditions at room temperature within a very short reaction time. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fast and Eco-friendly Synthesis of Dipyrromethanes by H2SO4·SiO2 Catalysis under Solvent-free ConditionsCHINESE JOURNAL OF CHEMISTRY, Issue 2 2010Yan Zhang Abstract For the first time, sillica-supported sulfuric acid has been used as a heterogeneous, reusable and efficient catalyst at room temperature to give the corresponding dipyrromethanes in a very short reaction time. The new reaction procedure is simple and solvent is not required. [source] Convenient Microwave-Assisted Synthesis of 5-Functionalized 1,2,4-Triazolium Ylides Starting from N,,N, -Disubstituted CarbohydrazonamidesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2008Mehdi Khankischpur Abstract 5-Functionalized 1,2,4-triazolium ylides have been prepared in good yields and in very short reaction times by reacting N,,N, -disubstituted carbohydrazonamides with 1,1,-carbonylbis(1,2,4-triazole), 1,1,-thiocarbonyldiimidazole or diphenyl N -cyanimidocarbonate under microwave irradiation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Novel 4-Aminoquinolines through Microwave-Assisted SNAr Reactions: a Practical Route to Antimalarial AgentsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 36 2007Sergio Melato Abstract 4-Aminoquinolines have recently been indicated to be an important class of chemotherapeutic agents for artemisinin-based antimalarial combination therapy. A rapid, cheap, possibly clean and scalable route to 4-aminoquinolines endowed with multiple diversity is therefore badly needed. Classically, they have been prepared by means of SNAr reactions, requiring hazardous or costly reagents and conditions and complex purification procedures. In this paper, microwave flash-heating chemistry is shown to allow the efficient conversion of the available 4,7-dichloroquinoline into a library of aminoquinolines in high yields and purities, with no need for further purification steps and requiring very short reaction times. Some of the compounds in this library were active against chloroquine-sensitive and chloroquine-resistant parasite strains.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Highly Efficient Synthesis of New ,-Arylamino-,,-chloropropan-2-ones via Oxidative Hydrolysis of Vinyl Chlorides Promoted by Calcium HypochloriteADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Vittorio Pace Abstract The oxidative hydrolysis of different trifluoroacetyl-protected N -(2-chloroallyl)anilines, promoted by calcium hypochlorite, is able to yield several not previously described ,-arylamino-,,-chloropropan-2-ones, very valuable building blocks that are useful as precursors of several drugs, in excellent yields and short reaction times. The main requirement of the reaction for avoiding the undesired aromatic chlorination (N -protection) is effectively solved by the use of the easily formed and removed N -trifluoroacetyl group. Thus, it is possible to perform the oxidative hydrolysis-deprotection step using a one-pot strategy, obtaining quantitative yields in very short reaction times. [source] Diethylzinc: A Simple and Efficient Catalyst for the Swift Hydroamination at Room TemperatureADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Jens-Wolfgang Pissarek Abstract Diethylzinc and dimethylanilinium tetrakis(pentafluorophenyl)borate were found to catalyze hydroaminations at room temperature in high efficiency and very short reaction times. The reactivity of the proposed cationic zinc species, which is assumed to catalyze the reaction, strongly depends on the coordinative abilities of the counterion. [source] Highly Convenient, Clean, Fast, and Reliable Sonogashira Coupling Reactions Promoted by Aminophosphine-Based Pincer Complexes of Palladium Performed under Additive- and Amine-Free Reaction ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2009Jeanne Abstract Sequential addition of 1,1,,1,,-phosphinetriyltripiperidine and 1,3-diaminobenzene or resorcinol to toluene solutions of (cyclooctadiene)palladium dichloride [Pd(cod)(Cl)2] under nitrogen in "one pot" almost quantitatively yielded the aminophosphine-based pincer complexes {[C6H3 -2,6-(XP{piperidinyl}2)2]Pd(Cl)} (X=NH 1; X=O 2). Complex 1 (and to a minor extent 2) proved to be efficient Sonogashira catalysts, which allow the quantitative coupling of various electronically deactivated and/or sterically hindered and functionalized aryl iodides and aryl bromides with several alkynes as coupling partners within very short reaction times and low catalyst loadings. Importantly, in contrast to most of the Sonogashira catalysts, which either are both air- and moisture-sensitive and/or require the addition of co-catalysts, such as copper(I) iodide [CuI], for example, or a large excess of an amine, the coupling reactions were carried out without the use of amines, co-catalysts or other aditives and without exclusion of air and moisture. Moreover, the desired products were exclusively formed (no side-products were detected) without employing an excess of one of the substrates. Ethylene glycol and potassium phosphate (K3PO4) were found to be the ideal solvent and base for this transformation. Experimental observations strongly indicate that palladium nanoparticles are not the catalytically active form of 1 and 2. On the other hand, their transformation into another homogeneous catalytically active species cannot be excluded. [source] Synthesis of N-Heteroaryl(trifluoromethyl)hydroxyalkanoic Acid Esters by Highly Efficient Solid Acid-Catalyzed Hydroxyalkylation of Indoles and Pyrroles with Activated Trifluoromethyl KetonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14 2005Mohammed Abid Abstract The synthesis of N-heteroaryl(trifluoromethyl)hydroxyalkanoic acid esters by solid acid-catalyzed Friedel,Crafts hydroxyalkylation of indoles and pyrroles with ethyl 3,3,3-trifluoropyruvate and ethyl 4,4,4-trifluoroacetoacetate is described. The inexpensive and readily available K-10 montmorillonite is found to be an efficient catalyst for the synthesis of a wide variety of trifluoromethylated indol-3-yl- and pyrrol-2-yl-hydroxypropionic and -butanoic acid esters. Using a series of substituted indoles and pyrroles the corresponding products were isolated in excellent yield (up to 98%) and 100% selectivity under mild experimental conditions, during very short reaction times. Beyond these, the ease of product isolation, catalyst stability and handling make this process an attractive, environmentally benign alternative for the synthesis of the target compounds. [source] | ||||||||||