- Pyrazoles: 'one-pot' synthesis from arenes and carboxylic acids
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A rapid and efficient method for 'one-pot' synthesis of pyrazoles from (hetero)arenes and carboxylic acids via successive formation of ketones and β-diketones followed by heterocyclization with hydrazine has been developed. The utility of the RCOOH/TfOH/TFAA acylation system for intermediate production of ketones and 1,3-diketones is a key feature of this approach. The preliminary evaluation of the anticancer activity of the synthesized pyrazoles is performed.
- Gong, Ming,Kim, Jung Keun,Kovalev, Vladimir V.,Kovaleva, Olga V.,Shokova, Elvira A.,Tafeenko, Viktor A.,Wu, Yangjie
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p. 5625 - 5638
(2020/08/21)
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- Sodium carbonate as a solid-phase reagent for the generation of acetylketene
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Reaction of a toluene solution of 3-oxobutanoyl chloride (14) with Na2CO3 in the presence of a catalytic amount of triethylamine at -78 °C generates a solution of acetylketene (2), the dimer of which was isolated. Acetylketene (2) was trapped with 2-propanone, 2-propanol, and ethyl vinyl ether.
- Bell, Kelcey,Sadasivam, Dhandapani V.,Gudipati, Indra Reddy,Ji, Hua,Birney, David
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body text
p. 1295 - 1297
(2009/09/06)
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- Studies on the stereochemistry of 1,2,6-trimethyl-4-piperidone
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In the effort to create new derivatives of analgesically active spiropiperidines intermediate 1,2,6-trimethyl-4-piperidone was synthesized. The substitution of the skeleton gives rise to configurational as well as conformational isomerism. Despite the symmetry of 1,2,6-trimethyl-4-piperidone two different sets of signals were present in the 1H and 13C NMR spectra. They were supposed to arise from a cis/trans mixture of 1,2,6-trimethyl-4-piperidone. In contrast to this explanation only two signals of the methyl groups and hydrogens at carbon atoms 2 and 6 were observed in the 1H and 13C NMR spectra, normally expecting one for the cis- and two for the trans-isomer. To solve this discrepancy, the kind of isomeric mixture of 1,2,6-trimethyl-4-piperidone leading to the 1H and 13C NMR spectra was examined. Energy differences between chair conformations of both the cis- and the trans-isomer of 1,2,6-trimethyl-4- piperidone and the potential energy surface of the equilibration process of the trans-isomer of 1,2,6-trimethyl-4-piperidone between its chair conformers were determined by quantum chemical calculations. The barrier height of the equilibration process was measured by high and low temperature NMR measurements to confirm the theoretical outcome. The results of all investigations agree nicely and proved a cis-/trans-mixture of 1,2,6-trimethyl-4-piperidone being present at room temperature.
- Diwischek, Florian,Arnone, Mario,Engels, Bernd,Holzgrabe, Ulrike
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p. 6993 - 7001
(2007/10/03)
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- Gas-Phase Kinetics of Elimination Reactions of Pentane-2,4-Dione Derivatives
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Gas-phase elimination reactions of pentane-2,4-dione, methyl acetoacetate, ethyl acetoacetate, 3-phenylhydroazopentane-2,4-dione, and ethyl 3-oxo-2-phenylhydrazonobutyrate have been measured in the temperature ranges of 744-783, 662-695, 614-663, 604-664, and 503-555 K, respectively, using a flow-thermolysis technique.These compounds undergo unimolecular first-order elimination reactions, for which log A = 11.9, 11.2, 11.7, 11.5, and 11.7 s-1 and Ea = 198.3, 167.1, 141.7, 165.6, and 141.7 kJ mol-1, respectively.The kinetic data and product analysis shows that the reactions are highly affected by the electronic nature of the substituents at the carbonyl and methylene carbon atoms of the substrates investigated.
- Al-Awadi, Nouria A.,El-Nagdi, Mohamed H.,Mathew, Tommy
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p. 517 - 524
(2007/10/02)
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- Direct Observation of α-Oxo Ketenes Formed from 1,3-Dioxin-4-ones and the Enols of β-Keto Esters
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The enol forms of β-keto esters thermolyze to alcohols and α-oxo ketenes, which are characterized by low-temperature IR spectroscopy and on warming regenerate the β-hydroxy-α,β-unsaturated esters. The matrix isolated s-Z and s-E forms of α-oxo ketenes are characterized and photochemically converted into other conformers or sites.Matrix photolysis of 2,2,6-trimethyl-1,3-dioxin-4-one gives the s-Z acetylketene initially. α-Oxo ketenes polymerize in the cold and dimerize only at elevated temperatures.
- Freiermuth, Beat,Wentrup, Curt
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p. 2286 - 2289
(2007/10/02)
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- Two Unusual Trimers of Diketene
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Formation of two unknown, tricyclic trimers of diketene, 3 and 4, was observed in diketene solutions containing (CH3)3SiCl/NaI or TsOH.
- Ernest, Ivan,Fritz, Hans,Rihs, Grety
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p. 203 - 209
(2007/10/02)
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- 1,3-Oxazines and Related Compounds. IX. Alkylation, Acylation, and Cleavage Reaction of 6-Methyl-4-oxo-2-thioxo-3,4-dihydro-2H-1,3-oxazine
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Alkylation of the title compound (2) with alkyl halides in the presence of Et3N proceeded exclusively on the sulfur atom to give the alkyl-1,3-oxazine derivatives.Acylation with acyl chlorides took place regioselectively on the nitrogen atom, giving the N-acyl derivatives. 1,3-Oxazine 2 was found to undergo cleavage of the ring into acetylketene and thiocyanic acid.Hence, treatment of 2 with alkyl halides in the presence of K2CO3 gave alkyl thiocyanates; treatment with active methylene compounds afforded γ-pyrone derivatives.N-Acyl derivatives of 2 also underwent thermal cleavage of the ring, leading to the corresponding acyl isothiocyanates.Keywords - 2-thioxo-4-oxo-1,3-oxazine; acetylketene; thiocyanic acid; acyl isothiocyanate; alkyl thiocyanate; acylation; alkylation; substituted γ-pyrone.
- Yamamoto, Yutaka,Morita, Yasuo
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p. 2957 - 2962
(2007/10/02)
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- Thermal Decomposition of 2,2,6-Trimethyl-4H-1,3-dioxin-4-one and 1-Ethoxybutyn-3-one. Acetylketene
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Acetylketene was first mentioned in the literature in 1907, but only in recent years has evidence for the existence of this species appeared.Previous work has indicated that acetylketene may be generated by pyrolysis of the title dioxinone, and we now present further chemical evidence in support of its presence.In particular, ethoxyacetylenes are known to generate ketenes upon pyrolysis.When the title alkyne was heated, it provided an intermediate that in six different trapping experiments gave the same products as those obtained via pyrolysis of the dioxinone.Acetylketene chemistry is predominated by -cycloaddition reactions; no evidence for conversion to β-crotonolactone or diketene was seen.
- Hyatt, John A.,Feldman, Paul L.,Clemens, Robert J.
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p. 5105 - 5108
(2007/10/02)
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- Formation of Cyclic Carbonates in the Reaction of 1,2-Ditertiary Diols with Acetic Anhydride and 4-(Dimethylamino)pyridine
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The reaction of 1,2-ditertiary diol 1a with acetic anhydride and 4-(dimethylamino)pyridine (DMAP) at high concentrations in the absence of solvent has been found to give rise to cyclic carbonate 2a.The reaction has been generalized with a few other 1,2-ditertiary diols (1b-d).Based on the different products isolated in these reactions, apart from a small amount of normal acetylation products, various mechanisms have been proposed and examined.Tertiary alcohols have been found to give monoacetoacetates in addition to the acetates, under the same conditions.Detailedinvestigations have prompted us to suggest the intermediacy of ketene and diketene in these reactions.
- Bhushan, Vidya,Chakraborty, Thushar K.,Chandrasekaran, Srinivasan
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p. 3974 - 3978
(2007/10/02)
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- ACYLATION OF 2-AMINO-5-PHENYL-4-OXAZOLINONE AND 2-AMINO-4-IMIDAZOLINONES
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The acylation of 2-amino-5-phenyl-4-oxazolinone and 2-amino-1-methyl-4-imidazolinone with acetyl chloride in benzene in the presence of triethylamine leads to the formation of 2-acetamido-5-phenyl-4-oxazolinone and 2-acetamido-1-methyl-4-imidazolinone.The acylation of 2-amino-4-imidazolinone under the indicated conditions, as well as acetic anhydride, gives 1-acetylimidazolidine-2,4-dione. 3-Acetyl-6-methyl-2H-pyran-2,4(3H)-dione (dehydroacetic acid) is formed as a side product in the acylation of 2-amino-4-azolinones with acetyl chloride in benzene in the presence of triethylamine.The IR and PMR spectra of the compounds obtained are presented.
- Ramsh, S. M.,Zheltonog, N. G.,Shamina, L. P.,Basova, Yu. G.,Ginak, A. I.
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p. 481 - 484
(2007/10/02)
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- Reaction of Diketene-Acetone Adduct with Enamines, Ketene Acetals, Vinyl Ethers, and β-Diketones
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Diketene-acetone adduct (1) generates acetylketene (2) under heating.In order to compare the reactivity of 2 with that of diketene, the reaction of 1 with electron-rich olefins was investigated.On heating with 1 primary enamines (3a-d) produced the corresponding 3-substituted 2,6-dimethyl-4(1H)-pyridones (4a-d), while the tertiary enamine 3e gave the 4-pyrone derivative (7).The reaction of 1 with ketene acetals (8) gave the 2,2-diethoxy-2,3-dihydro-4-pyrone derivatives (9).The vinyl ether derivatives 13 similarly reacted with 1 to give the 4-pyrone derivative 15 or 16 as the major product.The result shows that both diketene and 2 react with electron-rich olefins in a similar manner.Keywords -- diketene; acetylketene; diketene-acetone adduct; enamine; ketene acetal; vinyl ether; 1,3-dioxin-4-one; 4-pyridone; 4-pyrone; cycloaddition
- Sato, Masayuki,Ogasawara, Hiromischi,Kato, Keiko,Sakai, Masako,Kato, Tetsuzo
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p. 4300 - 4305
(2007/10/02)
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