Aromatic carboxylic acids are obtained in good to excellent yield essentially free of diaryl ketones by carboxylation of aromatics with a carbon dioxide-Al(2)Cl(6)/Al system at moderate temperatures (20-80 degrees C). To optimize reaction conditions and study the reaction mechanism, experimental variables including temperature, amount of Al(2)Cl(6)/Al, various Lewis acids, role of metal additive, carbon dioxide pressure, etc. were studied. The carboxylation reaction was found to be stoichiometric rather than catalytic, with aluminum chloride forming a dichloroaluminate of carboxylic acids. Although the carboxylation takes place using AlCl(3) itself, the presence of metal additives, especially Al, increased the yield and selectivity of carboxylic acids. Because it was not possible to distinguish between two possible mechanistic pathways of the reaction on the basis of the experimental results, theoretical calculations using density functional theory (DFT) were also carried out. One possible pathway involves an initial complex between benzene and Al(2)Cl(6), with subsequent formation of organoaluminum intermediates (PhAlCl(2) and PhAl(2)Cl(5)). The other proceeds through the formation of various complexes of CO(2) with aluminum chloride (AlCl(3))(n), n = 1-4. The calculations have shown that the organometallic pathway, leading eventually through the formation of phenylaluminum dichloride, is endothermic by 33 kcal/mol. In contrast, the preferred CO(2)-AlCl(3) complex forms in an exothermic reaction (-6.0 kcal/mol) as does CO(2)AlCl(2)(+). On the basis of both experimental and calculational findings, the most feasible reaction mechanism proposed involves superelectrophilic aluminum chloride activated carbon dioxide reacting with the aromatics in a typical electrophilic substitution.

γ‐C−H agostic stabilization of the 14‐electron metal center by a saturated hydrocarbon group characterizes the structure of the first neutral, three‐coordinate alkylrhodium(I) complex [(κ2‐dtbpm)RhNp] (1; dtbpm = bis(di‐tert‐butylphosphanyl)methane, Np=neopentyl). Some of its reactions, for example, N2 complexation and C−H bond activation, are reported.

For Abstract see ChemInform Abstract in Full Text.

The one-pot synthesis of 1,1,1-trifluoro- and 1,1-difluoro-2,2-diarylethanes from arenes and fluorinated hemiacetals in the BF(3)-H(2)O system is described. The reaction is simple, clean, and convenient, eliminating the use of organic solvents and other expensive acid systems. BF(3)-H(2)O is economic, is easy to prepare, and offers ample acidity required for this reaction.

Selective activation and functionalization of alkanes by transition metals is a highly attractive goal [1] which has led to considerable efforts to understand hydrocarbon interactions

Mitte November vergangenen Jahres fand in Leverkusen das 1. Internationale Katalyse‐Symposium statt. Zu dieser Veranstaltung der Bayer Chemicals fanden sich über 200 Forscher aus Industrie und Hochschule ein.

diarylethanes. -The reaction substrate (I) with various arenes is mediated by BF3·Et2O or TFA with comparable yields. In the latter case, the reaction time is reduced. Nitrobenzene affords only the intermediate carbinol (V). Monosubstituted arenes mostly afford inseparable mixtures. The reaction with hemiacetal (VI) proceeds under mild conditions and with high regioselectivity. -(PRAKASH*, G. K. S.; PAKNIA, F.; MATHEW, T.; MLOSTON, G.; JOSCHEK, J. P.; OLAH, G. A.; Org. Lett. 13 (2011) 15, 4128-4131, http://dx.