Preparation of Esters from the Reaction of Alkyl Orthosilicates with Organic Acids

On the Interactions of Alkyl 2‐Hydroxycarboxylic Acids with Alkoxysilanes: Selective Esterification of Simple 2‐Hydroxycarboxylic Acids

“…The reaction of carboxylic acids with alkoxysilanes has been studied since at least 1928 [9] and been suggested as a method for the preparation of esters since 1956, [10] but the mechanism was for a long time unclear. Mechanisms involving acid-siloxane complexes as intermediates, such as that outlined in the introduction (steps 1 a-1 c), originate with Andrianov et al who, in the 1950s, proposed that during the reaction of Et 2 SiA C H T U N G T R E N N U N G (OEt) 2 with AcOH (or other acids) in toluene, [29] the acid displaced an alkoxy ligand giving Et 2 Si- 2 , which was the final product if EtOH was removed by distillation, but otherwise might react with EtOH to give EtOAc, and, by condensation, polydiethylsiloxanes.…”

“…The mechanism has implications for the use of 2HOAs as templates in sol-gel silica preparation. Keywords: homogeneous catalysis · mass spectrometry · NMR spectroscopy · silicates · siloxanes Although the reaction of carboxylic acids with alkoxysilanes has been known to produce carboxylate esters, as well as causing siloxane oligomerisation, dependent on the conditions, for many years, [9,10] there has been no report of the selectivity of this reaction for 2HOAs. In fact the production of carboxylate esters has been observed not only in this reaction, but also in those of carboxylic anhydrides with alkoxysilanes, [11] alcohols with acyloxysilanes [12,13] and ternary reactions of carboxylic acids with chlorosilanes and alcohols; [14] however, in each case, the literature is divided over the actual mechanisms.…”

Preparation of organoalkoxysiloxanes by partial acidolysis of organoalkoxysilanes

“…Branched organosilsesquioxanes can also include the fragments of the ladder, three-dimensional, and polycyclic structures [11][12][13][14][15][16][17].…”

“…Based on the kinetic data, on the composition, properties, and the 29 Si NMR spectroscopy data of the products the conclusion is made that the obtained compounds have polycyclic structure with branched fragments. Using the GLC method the reaction was shown to have an induction period, whose duration can be substantially shortened by addition of HCl or methanol.Reactions of organoacetoxysilanes with alcohols [1, 2] and organoalkoxysilanes with organic acids [3][4][5][6][7][8][9][10][11][12][13] are an efficient method of synthesis of organosiloxanes of various composition and structure. A specific feature of these processes is the formation of the siloxane bond upon hydrolytic polycondensation in homogeneous environment due to the presence of water produced in the reaction of an acid with an alcohol.…”

“…Reactions of organoacetoxysilanes with alcohols [1,2] and organoalkoxysilanes with organic acids [3][4][5][6][7][8][9][10][11][12][13] are an efficient method of synthesis of organosiloxanes of various composition and structure. A specific feature of these processes is the formation of the siloxane bond upon hydrolytic polycondensation in homogeneous environment due to the presence of water produced in the reaction of an acid with an alcohol.…”