Esterification s. Carboxylic

Esterification s. Carboxylic acid esters from carboxylic acids, Redoxesterification Esters, active s. Carboxylic acid esters, active Etherates s. Alane etherates Ethers (s. a. Alkoxy...,... 

Ester enolates 27, 843 suppl. 29 Esterification s. Carboxylic acid esters from carboxylic acids... 

In this definition ko is the rate constant for CH3COOR and k is the constant for RCOOR thus = 0 for R = CH3. Table 7-11 lists some values. Taft s Es steric constants are in some instances based on averages of several different reactions, so MacPhee et al. have defined a steric constant Es by Eq. (7-52) for a single reaction, namely, the acid-catalyzed esterification of carboxylic acids in methanol at 40°C. Es values are also given in Table 7-11. Additional Es and Es values are available. 

Shieh, W. and Dell, S. and Repic, 0. (2002). Large scale microwave-accelerated esterification of carboxylic acids with dimethyl carbonate. Tetrahedron Letters, 43, 5607-5609. 

Price and Hammett s rule has found confirmation in the reaction of benzaldehyde with acetone and ethyl methyl ketone (Gettler and Hammett, 1943), in the acid-catalyzed hydration of olefins (Taft, 1956a), in the hydrolysis of esters catalyzed by ion-exchange resins (Samelson and Hammett, 1956), in acid-catalyzed deoxymercuration (Kreevoy et al., 1962), and in the esterification of carboxylic acids in methanol (Smith, 1939). Taft (1956b) has noted that the rule seems to require the following modifications. The entropy-bearing substituent... 

Shieh, W.-C. Dell, S. Repic, O. Nucleophilic catalysis with DBU for the esterification of carboxylic acids with dimethyl carbonate. J. Org. Chem. 2002, 67, 2188-2191. 

Table V summarizes several reactions that have been demonstrated on a laboratory scale 1 know of no industrialized chemical process using Nafion as a superacid catalyst. Although many of the reactions were carried out with stirring a mixture of reactants and Nafion-H, several alkylation, disproportionation, rearrangement, and esterification reactions were performed by means of the flow-reaction method in the liquid or gas phase. For instance, in the esterification of carboxylic acids with alcohols, when a mixture of the acid and alcohol was allowed to flow over a Nafion-H catalyst at 95-125°C with a contact time 5 s, high yields, usually S90%, of the corresponding ester were obtained (82). It had been found that no reactivation of the catalyst was needed because the catalytic activity of the Nafion remained unchanged for prolonged periods of operation.

O-and S-Akylation. This base facilitates esterification of carboxylic acids1 and S-alkylation of p-toluenesulfinic acids.2... 

The Dubois steric constant E s is a revised Taft steric constant defined using the acid-catalyzed esterification of carboxylic acids (at 40 °C) as reference reaction [MacPhee, Panaye et al, 1978a, 1978b]. 

A differently anchored Mukaiyama reagent is the N-methylpyridinium iodide salt 57 [71], which has been obtained by reaction of the Merrifield resin with N-Boc-aminocaproic acid in the presence of cesium carbonate to give the supported ester 55 (Scheme 7.19). Further Boc-deprotection and reaction with 6-chloronicoti-noyl chloride in the presence of Hxinig s base furnished the anchored 2-chloro-pyridine 56, which was transformed into the final N-methylpyridinium salt 57 after N-methylation in neat methyl iodide. This supported reagent has been used in the rapid microwave-assisted esterification of carboxylic acids and alcohols in the presence of triethylamine as base, with dichloromethane as solvent at 80 °C, the products being obtained in high purity after simple resin filtration [72],... 

H. Kita, S. Sasaki, K. Tanaka, K. Okamoto and M. Yamamoto, Esterification of carboxylic acid with ethanol accompanied by pervaporation, Chem. Lett., 1988, 2025. 

STEGLICH HASSNER Dirad esterification Direct room temperature esterification of carboxylic acids with alcohols, Including ten alcohols with the help of dfcydohexytcartxxSimide (DCC) and S-dtekylamnopyridlne catalysts 3. 

Alkylative esterification of carboxylic acids with alkyl halides are effected by action with TMG (1) [65]. An ester is given by the TMG (1) mediated reaction of y-hydroxy-a,p-unsaturated carboxylic acid with methyl iodide without lactone formation after isomerization [65a]. Barton s base effectively works in the alkylation of sterically hindered carboxylic acid [3]. Ethanolysis of the acetate of tertiary alcohol occurred easily in 86% yield in the presence of BTMG (2) [66] (Scheme 4.24). 

Chakraborti, A.K., Singh, B., Chankeshwara, S.V., Patel, A.R. 2009. Protic acid immobilized on solid support as an extremely efficient recyclable catalyst system for a direct and atom economical esterification of carboxylic acids with alcohols. Journal of Organic Chemistry 74 5967-5974. 

The mechanism for acid-catalyzed esterification of carboxylic acids is completely reversible, but is driven to the right (toward the ester product) but application of Le Chatelier s principle and removal of water (also see Chapter 18, Section 18.6.3). Another application of Le Chatelier s principle uses a large excess of the alcohol (butanol for the formation of 70) to shift the equilibrium toward the ester by increasing the probability that it will react with alcohol rather than with water. Note that if ester 70 is treated with an acid catalyst and water rather than butanol, the mechanism shown will convert the ester back to the acid. In other words, if water replaces butanol, the mechanism from 70 to 21 is that for acid-catalyzed hydrolysis of an ester to a carboxylic acid (Section 20.2). 

Esterification of carboxylic acid 7 followed by ring closure metathesis (RCM) of h/s-olefin 16 to unsaturated azathilone 2 (Scheme 16.5) [26-28]. 

In contrast to carbodiimides, trichloroacetonitrile reacts neither with phosphoric acid diesters nor with carboxylic acids. F. esterification s. F. D. Gramer and G. Weimann, Ghem. Ind. 1960, 46. 

Polymeric amines can be proton acceptors, acyl transfer agents, or ligands for metal ions. The 2- and 4-isomers of poly(vinylpyridine) (11) and (12) and the weakly basic ion exchange resins, p-dimethylaminomethylated PS (2) and poly(2-dimethylaminoethyl acrylate), are commercial. The ion exchange resins are catalysts for aldol condensations, Knoevenagel condensations, Perkin reactions, cyanohydrin formation and redistributions of chlorosilanes. " The poly(vinylpyridine)s have been used in stoichiometric amounts for preparation of esters from acid chlorides and alcohols, and for preparation of trimethylsilyl ethers and trimethylsilylamines from chlorotrimethylsilane and alcohols or amines. Polymer-suppored DBU (l,8-diazabicyclo[5.4.0]undec-7-ene) (52) in stoichiometric amounts promotes dehydrohalogenation of alkyl bromides and esterification of carboxylic acids with alkyl halides. The protonated tertiary amine resins are converted to free base form by treatment with aqueous sodium hydroxide. 

List [86] and Jorgensen [87] have recently independently described a novel application of L-proline (107) for catalysis of enantioselective hydrazidation of aldehydes [88]. For example, when aldehyde 106 is allowed to react with di-tert-butyl azodicarboxylate (95) in the presence of 10 mol% 107, adduct 108 is isolated in > 90% yield and 93% ee (Scheme 10.18) [87]. The product hydra-zides can be transformed into protected amino acid derivatives through a sequence that involves oxidation of the aldehyde to the corresponding carboxylic acid, esterification, deprotection, and N-N bond cleavage with Raney-Ni [86, 87]. The observed selectivity has been attributed to the intervention of transition state 111 [86]. This structure incorporates a hydrogen bond between proline s carboxyl group and the azodicarboxylate as a key organizing feature. The transition state structure has parallels to that proposed for the proline-cata-lyzed aldol addition reactions and is supported by quantum mechanical studies by Houk [89]. 

Esterification with poly(carboxyhc anhydride)s can be controUed to minimize diesterification and cross-linking to produce carboxylated ceUulosic... 

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