- Solvent and structural effects on the activation parameters of the reaction of carboxylic acids with diazodiphenylmethane
-
The kinetics of the reaction of benzoic, 2-methylbenzoic, phenylacetic, cyclohex-1-enecarboxylic, 2-methylcyclohex-1-enecarboxylic, and cyclohex-1-eneacetic acids with diazodiphenylmethane was studied at 30, 33, 37, 40, and 45°C in a set of 12 protic and aprotic solvents. The reactions were found to follow the second-order kinetics. The activation energy as well as the activation parameters, such as the standard entropy, the standard enthalpy, and the standard Gibbs energy of the activation, was calculated from the second-order rate constants. The solvent and structural effects on the activation energy and the standard Gibbs energy of activation, for each examined compound, were analyzed. The results of Kamlet-Taft multiple correlation analysis show that the specific solvent-solute interactions play a dominant role in the governing of the reaction. The signs of the equation coefficients support the proposed reaction mechanism.
- Nikolic,Uscumlic
-
-
Read Online
- Catalytic enantioselective nazarov cyclization: Construction of vicinal all-carbon-atom quaternary stereocenters
-
The diastereoselective asymmetric synthesis of vicinal all-carbon-atom quaternary stereocenters is a challenging problem in organic synthesis for which only few solutions have been described. A catalytic asymmetric Nazarov cyclization of fully substituted dienones that provides cyclopentenone derivatives with vicinal quaternary stereocenters in high optical purity and as single diastereoisomers is now reported.
- Jolit, Anais,Walleser, Patrick M.,Yap, Glenn P. A.,Tius, Marcus A.
-
supporting information
p. 6180 - 6183
(2014/06/23)
-
- Diastereospecific nazarov cyclization of fully substituted dienones: Generation of vicinal all-carbon-atom quaternary stereocenters
-
No vacancy: Fully substituted dienones that are highly polarized by a vinylogous carbonate group were found to undergo a remarkably rapid and diastereospecific Nazarov cyclization that led to cyclopentenones with vicinal all-carbon-atom quaternary centers (see example; SEM=2-(trimethylsilyl) ethoxymethyl, Tf=trifluoromethanesulfonyl). Copyright
- Jolit, Anais,Vazquez-Rodriguez, Saleta,Yap, Glenn P. A.,Tius, Marcus A.
-
supporting information
p. 11102 - 11105
(2013/10/22)
-
- Asymmetric synthesis of 2-methyl cyclohexane carboxylic acids by heterogeneous catalysis: Mechanistic aspects
-
The catalytic hydrogenation of (S)-alkyl-N-(2-methylbenzoyl)pyroglutamates was studied over supported rhodium and ruthenium catalysts at room temperature and a pressure of 5 MPa. The reaction was diastereoselective with the predominant formation of (1S,2R)-2-methylcyclohexane carboxylic acid with a diastereomeric excess (de) of up to 96%. The most stable conformation was determined by means of a combination of modelling calculations, NMR spectroscopy and X-ray structural determination. In this conformation, the carbonyl group of the pyroglutamate auxiliary shields one face of the aromatic ring. The observed selectivity may thus be explained by a preferential adsorption at the unshielded face which avoids steric repulsion by the C=O group to result in a cis hydrogenation. The addition of an amine, the nature of the support (alumina or active carbon) or of the metal (Rh or Ru) were shown to give additional stabilisation of the adsorption at the unshielded face to increase the diastereoisomeric excess.
- Besson, Michele,Delbecq, Francoise,Gallezot, Pierre,Neto, Samuel,Pinel, Catherine
-
p. 949 - 958
(2007/10/03)
-
- Preferential Oxygenation of 4-Cycloalkylideneoxazol-5(4H)-ones: Synthesis of N-Acylcycloalk-1-enecarboxamides
-
The addition of oxygen, in the presence of base, to 4-cycloalkylideneoxazol-5(4H)-ones led to new substituted N-acylcycloalkenecarboxamides in high yiedl, via base-catalysed isomerisation, oxygenation and subsequent fragmentation of a hydro- or endo-peroxide intermediate.
- Lalitha, Nagabundi,Bhalerao, Uday Triamakraj,Iyengar, Divi Sarangapani
-
p. 737 - 738
(2007/10/02)
-
- The Reactivity of 2-Substituted Cyclohex-1-enecarboxylic Acid With Diazodiphenylmethane in Various Alcohols
-
The reactivities of 2-substituted cyclohex-1-enecarboxylic acids with diazodiphenylmethane in several alcohols were investigated.The rate data for these acids were correlated with a simple Hammett equation by means of the ?p constants.The transmission of polar effects through the double bond, in terms of polar susceptibility constant ρ, has been discussed.For the reactions of a given acid in the various alcohols, the log k and ρ values were correlated through multiple regression on appropriate solvent parameters.The results obtained for 2-substituted cyclohex-1-enecarboxylic acids were compared with the results for ortho-substituted benzoic acids under the same experimental conditions.
- Uscumlic, Gordana S.,Krstic, Vera V.,Muskatirovic, Milan D.
-
p. 999 - 1002
(2007/10/02)
-