Esterifications of carboxylic acids and alcohols catalyzed by Al 2(SO4)3 · 18H2O under solvent-free condition
Esterifications of equimolar mixture of carboxylic acids and alcohols can be effectively catalyzed by Al2(SO4)3 · 18H2O under solvent-free condition. The esterification catalyzed by Al2(SO4)3 · 18H2O is a promising green method thanks to no need of organic solvent, no pollution, no causticity and ease to handle after reaction. This catalyst is of a low toxicity (usually it is used as purifying agent for drinking water), low-cost compound and is easily separated from the reaction mixture by simple filtration. Moreover, the catalyst can be recycled for the further esterification and the conversion does not evidently decrease.
Gang, Li,Wenhui, Pang
experimental part
p. 559 - 565
(2011/01/07)
A mild and efficient method for esterification and transesterification catalyzed by iodine
Iodine, was found to be a practical and useful Lewis acid catalyst for the esterification of carboxylic acids with alcohols. The high catalytic activity of iodine can be used for the transesterification of esters by different alcohols including tertiary alcohols and sterically hindered primary and secondary alcohols. The method presented is especially effective for simultaneous esterification and transesterification reactions.
Ramalinga,Vijayalakshmi,Kaimal
p. 879 - 882
(2007/10/03)
The synthesis of esters under microwave irradiation using dry-media conditions
Practical and simple techniques are described for using nonmodified domestic microwave ovens as safe and convenient laboratory devices to obtain numerous esters.High pressures are avoided by conducting reactions with reactants impregnated on solid mineral supports in "dry media" or by phase transfer catalysis (PTC) in the absence of organic solvents.Two kinds of microwave effects are involved: (1) displacement of the equilibrium by evaporation of volatile polar molecules (water or alcohols) in esterfications and transesterfications; (2) acceleration of ionic reactions in carboxylate alkylations.As solvents are avoided, there is no need for sealed vessels and water separators.
LACTONISIERUNG VON MAKROLID-SECOSAEUREN MIT "PUSH-PULL ACETYLENEN"
A highly efficient method for the macrolactonization of seco-acids is described.Seco-acids are converted into stable enolesters 3 by the acetylene 1, which are cyclized under proton or Lewis acid catalysis.This new method has been successfully applied to the lactonization of the 7-epi-brefeldin A seco-acids 8a, b.