- Methyl Group Effect on the Proton Affinity of Methylated Acetophenones Studied by Two Mass Spectrometric Techniques
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The proton affinities (PA) of all isomeric dimethylacetophenones were determined using the "kinetic method" with a tandem mass spectrometer and by measurements of the proton transfer equilibrium in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry.For both methods acetophenone and p-methylacetophenone, with well known PA values, were used as reference bases.Both methods yielded identical PA values for all dimethylacetophenones.The PA of the dimethylacetophenones were in a narrow range between 872 and 880 kJ mol-1 except for 2,6-dimethylacetophenone, for which a PA of 856 kJ mol-1 was found.The results are discussed in terms of possible mesomeric structures stabilizing the positive charge with regard to the substitution pattern in the phenyl ring.Obviously, the significant smaller PA of 2,6-dimethylacetophenone compared with the other isomers is due to the distortion of the conjugation of the C-O double bond with the aromatic ? system.
- Kukol, A.,Strehle, F.,Thielking, G.,Gruetzmacher, H.-Fr.
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- METHOD FOR PRODUCING 2',3'-DIMETHYL AROMATIC KETONE
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PROBLEM TO BE SOLVED: To provide a method for producing 2',3'-dimethyl aromatic ketone in which an inexpensive and easily available raw material is used and that can industrially manufacture 2',3'-dimethyl aromatic ketone that is inexpensive. SOLUTION: A 2',3'-Dimethyl aromatic ketone is produced by reacting 2,3-dimethylchlorobenzene with magnesium metal in the presence of lithium chloride of 0.2 mole times or more with respect to 2,3-dimethylchlorobenzene to convert into a Grignard reagent, and reacting the Grignard reagent with an acid anhydride at a reaction temperature of 10°C or lower, followed by subjecting to hydrolysis treatment. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPOandINPIT
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Paragraph 0031-0038
(2021/04/09)
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- Polystyrene supported Al(OTf)3: An environmentally friendly heterogeneous catalyst for Friedel-Crafts acylation of aromatic compounds
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Stable and non-hygroscopic polystyrene supported aluminium triflate (Ps-Al(OTf)3), which is prepared easily from cheap and commercially available compounds was found to be an environmentally friendly heterogeneous catalyst for Friedel-Crafts acylation of arenes using acid chlorides in the absence of solvent under mild reaction conditions. The catalyst can be reused up to five times after simple washing with dichloromethane.
- Boroujeni, Kaveh Parvanak
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experimental part
p. 3156 - 3158
(2012/05/20)
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- Hydrogen-bonding-promoted oxidative addition and regioselective arylation of olefins with aryl chlorides
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The first, general, and highly efficient catalytic system that allows a wide range of activated and unactivated aryl chlorides to couple regioselectively with olefins has been developed. The Heck arylation reaction is likely to be controlled by the oxidative addition of ArCl to Pd(0). Hence, an electron-rich diphosphine, 4-MeO-dppp, was introduced to facilitate the catalysis. Solvent choice is critical, however; only sluggish arylation is observed in DMF or DMSO, whereas the reaction proceeds well in ethylene glycol at 0.1-1 mol % catalyst loadings, displaying excellent regioselectivity. Mechanistic evidence supports that the arylation is turnover-limited by the oxidative addition step and, most importantly, that the oxidative addition is accelerated by ethylene glycol, most likely via hydrogen bonding to the chloride at the transition state as shown by DFT calculations. Ethylene glycol thus plays a double role in the arylation, facilitating oxidative addition and promoting the subsequent dissociation of chloride from Pd(II) to give a cationic Pd(II)-olefin species, which is key to the regioselectivity observed.
- Ruan, Jiwu,Iggo, Jonathan A.,Berry, Neil G.,Xiao, Jianliang
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supporting information; experimental part
p. 16689 - 16699
(2011/02/23)
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- 188. Addition of Carbon Nucleophiles to Tricarbonylchromium Complexes of 1,2-Dihydrocyclobutabenzene, Indane, 1,2,3,4-Tetrahydronaphthalene and ortho-Xylene
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3-Substituted 1,2-dihydrocyclobutabenzenes (bicycloocta-1,3,5-triene) are readily accessible from (1) via a two-step sequence which involves addition of a nucleophile and oxidation of the intermediate anionic
- Kuendig, E. Peter,Grivet, Chantal,Wenger, Eric,Bernardinelli, Gerald,Williams, Alan F.
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p. 2009 - 2023
(2007/10/02)
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- THE PHENYLCARBENE REARRANGEMENT REVISITED
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The evolution of mechanistic ideas about the phenylcarbene rearrangement has been reviewed, and three closely linked problems have been identified toward whose solution this research has been aimed: 1.Why do the ratios of the stable end products from the rearrangements of o-, m- and p-tolylmethylene differ when all three reactions have been thought to pass through a common intermediate? 2.Why does the rearrangement of 2-methylcycloheptatrienylidene lead to exclusive formation of styrene? 3.What is the mechanism of styrene formation from o-tolylmethylene? New mechanisms have been proposed in which m- and p-tolylmethylene can rearrange to styrene without necessarily being converted to o-tolylmethylene.The formation of a small amount of 2,6-dimethylstyrene from the rearrangement of 3,4,5-trimethylphenylmethylene is viewed as evidence for such a mechanism, and a set of interconverting norcaradienylidenes are believed to be the crucial intermediates.Other alternatives are considered and rejected on the basis of the rearrangement products of 3,5-dimethyl- and 3,4,5-trimethylphenylmethylene.
- Gaspar, Peter P.,Hsu, Jong-Pyng,Chari, Sarangan,Jones, Maitland Jr.
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p. 1479 - 1508
(2007/10/02)
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