Diphenylammonium triflate (DPAT): efficient catalyst for esterification of carboxylic acids and for transesterification of carboxylic esters with nearly equimolar amounts of alcohols

Zr(IV)Fe(III), Ga(III), and Sn(IV) Binary Metal Complexes as Synergistic and Reusable Esterification Catalysts

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Abstract: Synergism in catalytic activity with the combined use of Hf(O-i-Pr) 4 or Zr(O-i-Pr) 4 and Fe(O-i-Pr) 3 for direct esterification and a very simple method for their extraction with ionic liquids for their recovery and reuse are described. This Zr(IV) À Fe(III) complex is an environmentally benign catalyst due to its high turnover number, extremely mild Lewis acidity, low toxicity, reusability, and commercial availability at low cost.

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Direct ester condensation catalyzed by bulky diarylammonium pentafluorobenzenesulfonates

“…Among these 'green' catalytic condensations, metalfree organocatalytic methods are particularly desirable, especially for industrial processes. In 2000, Tanabe and co-workers 2 [OTf] À is the salt of a superacid (trifluoromethansulfonic acid (TfOH)) and a weak base (Ph 2 NH), it is a strong Brønsted acid, and as such is difficult to use in the reaction of sterically demanding and acid-sensitive alcohols.…”

“…For example, the condensation between cis-1,2-cyclohexanediol and 4-phenylbutyric acid with 4 gave the corresponding diester in 90% yield, while no esterification product was obtained by heating a mixture of 1,2-butanediol and 1-adamantanecarboxylic acid in toluene in the presence of HfCl 4 . (THF) 2 . In addition, we have been able to recover and reuse the bulky diarylammonium pentafluorobenzenesulfonate catalyst immobilized on a polystyrene support without any loss of catalytic activity more than 10 times 7,8 .…”

“…However, these have lower catalytic activities and the reactants that can be used are rather limited. With regard to green chemistry, in particular with respect to atom economy and E-factor, several catalytic methods for the ester condensation reaction between equimolar amounts of carboxylic acids and alcohols have been developed [2][3][4][5][6] . Conventionally, in fact, esterifications are conducted with an excess of carboxylic acids or alcohols against its reaction counterpart in the presence of an acid catalyst, or with a stoichiometric dehydrating reagent or activated carboxylic acid derivative in the presence of a stoichiometric amount of base.…”

ZrOCl2·8H2O: An Efficient, Cheap and Reusable Catalyst for the Esterification of Acrylic Acid and Other Carboxylic Acids with Equimolar Amounts of Alcohols

“…Esters are the important class of organic compounds, which are usually prepared by the esterification of carboxylic acids with alcohols catalyzed by H 2 SO 4 , TsOH [1,2] and other catalysts [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Because the esterification is a reversible reaction, in order to obtain a high yield of ester, an excess amount of one of the reactants is normally required, and/or removal of H 2 O by azeotropic distillation during the reaction is usually performed.…”