2142-71-4Relevant articles and documents
Methyl Group Effect on the Proton Affinity of Methylated Acetophenones Studied by Two Mass Spectrometric Techniques
Kukol, A.,Strehle, F.,Thielking, G.,Gruetzmacher, H.-Fr.
, p. 1107 - 1110 (1993)
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.
Polystyrene supported Al(OTf)3: An environmentally friendly heterogeneous catalyst for Friedel-Crafts acylation of aromatic compounds
Boroujeni, Kaveh Parvanak
experimental part, p. 3156 - 3158 (2012/05/20)
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.
Hydrogen-bonding-promoted oxidative addition and regioselective arylation of olefins with aryl chlorides
Ruan, Jiwu,Iggo, Jonathan A.,Berry, Neil G.,Xiao, Jianliang
supporting information; experimental part, p. 16689 - 16699 (2011/02/23)
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.
