Etherification transesterification

The most important examples of reactive separation processes (RSPs) are reactive distillation (RD), reactive absorption (RA), and reactive extraction (RE). In RD, reaction and distillation take place within the same zone of a distillation column. Reactants are converted to products, with simultaneous separation of the products and recycling of unused reactants. The RD process can be efficient in both size and cost of capital equipment and in energy used to achieve a complete conversion of reactants. Since reactor costs are often less than 10% of the capital investment, the combination of a relatively cheap reactor with a distillation column offers great potential for overall savings. Among suitable RD processes are etherifications, nitrations, esterifications, transesterifications, condensations, and alcylations (2). 

The proper stereochemistry was achieved by enzyme catalyzed desymmetrization of the prochiral 1,3-diol 30. Candida antarctica lipase (CAL)-catalyzed transesterification yielded the monoacetate 31, which gave rise to the methyl with the proper stereochemistry 32. The generation of the desired chiral epoxide 35 was achieved by asymmetric dihydroxylation employing AD-mix-a,42 followed by epoxide formation. Base-catalyzed etherification yielded the mixture of the enantiopure (+)-heliannuol A and (-)-heliannuol D. Unfortunately these compounds correspond to the opposite d/l series and correspond to the enantiomers of the natural products (-)-heliannuol A and (+)-heliannuol D (Fig. 5.6.A). 

Glycerol etherification is carried out at 260°C in a batch reactor at atmospheric pressure under N2 in the presence of 2 wt% of catalyst, water being eliminated and collected using a Dean-Stark system. Reagents and products are analysed with a GPC after silylation [5]. Batch processes are generally used in lipochemistry, especially for the esterification and transesterification reactions (except for the preparation of methyl esters). 

Examples. Either or both microwave reactors have been useful for processes such as esterification, amidation, transesterification, rearrangement, acetalization, nucleophilic substitution, hydrolysis of esters and amides, isomerization, decarboxylation, oxidation, elimination, etherification, and formation of aminoreductones. Examples of such reactions have been tabulated (2,3). 

Alcohols and derivatives. YbfOTf) serves as a catalyst for etherification of alcohols with 4-methoxybenzyl alcohols. Deacetylation of esters (particularly ArOAc) by transesterification to isopropanol is observed. A preparation of alkyl glycosides involves reaction of glycosyl esters with trialkyl borates in the presence of Yb(OTf)i. 

Reactive rectifications without a separate reactor, in which the reaction takes place in the distillation column, are increasingly being used in industry. Typical classes of reactions are esterification, transesterification, acetal formation and cleavage, etherification, oxidation, and hydrogenation. With regard to the design of such processes, three cases can be distinguished ... 

It was quickly realized that the SCF reactor was not restricted to hydrogenation reactions and could, in principle, be adapted to any type of solid or supported catalyst Successful reactions included Friedel-Crafts alkylation [36], etherification [37], hydroformylation [38], and base-catalyzed transesterification [39],... 

Some of the typical reactions that take place during an alkyd resin preparation and curing are (1) esterification, (2) alcoholysis, (3) ester interchange or transesterification, (4) etherification, (5) free radical addition reactions, (6) Diels-Alder reactions, (7) decarboxylations, and (8) polymerization via free radical initiation during curing (air-drying alkyds). 

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