Hydroxycarboxylic acid esters carboxylic

This procedure offers a convenient method for the esterification of carboxylic acids with alcohols2 and thiols2 under mild conditions. Its success depends on the high efficiency of 4-dialkylaminopyridines as nucleophilic catalysts 1n group transfer reactions. The esterification proceeds without the need of a preformed, activated carboxylic acid derivative, at room temperature, under nonacidic, mildly basic conditions. In addition to dichloromethane other aprotic solvents of comparable polarity such as diethyl ether, tetrahydrofuran, and acetonitrile can be used. The reaction can be applied to a wide variety of acids and alcohols, including polyols,2 6 a-hydroxycarboxylic acid esters,7 and even very acid labile... 

Startg. cyanophosphonic ester treated slowly with satd. KCN-soln. so that the temp, does not rise while the pH reaches 12 -> phosphoric ester (Y 94%) refluxed 12 hrs. in coned. HCl -> a-hydroxyundecanoic acid (Y 93%). - This is part of a synthesis of a-hydroxycarboxylic acids from carboxylic acid chlorides with addition of 1 C-atom. F. e. s. Y. Okamoto, T. Nitta, and H. Sakurai, Kogyo Kagaku Zasshi 71, 187 (1968) C. A. 69, 35342. 

Alkoxycarboxylic acids from hydroxycarboxylic acid esters via alkoxy-carboxylic acid esters—a,hydroxyl groups of aminophenols s. 11, 41... 

Figure 3.53 shows an addition of a carboxybc acid to isobutene, which takes place via the tert-butyl cation. This reaction is a method for forming ferf-butyl esters. Because the acid shown in Figure 3.53 is a /i-hydroxycarboxylic acid whose alcohol group adds to an additional isobutene molecule, this also shows an addition of a primary alcohol to isobutene, which takes place via the ferf-butyl cation. Because neither an ordinary carboxylic acid nor, of course, an alcohol is sufficiently acidic to protonate the alkene to give a carbenium ion, catalytic amounts of a mineral or sulfonic acid are also required here. 

Fig. 13.40. Alkylation of an ester enolate for the preparation of an a-hydroxycarboxylic acid (for the preparation of enantiomerically pure a-hydroxy carboxylic acid through alkylation of an enantiomerically pure ester enolate cf. Figure 13.41). The initially formed benzyl ester B contains two benzylic C—0 bonds, which can be cleaved by means of hydrogenolysis.

An aldol addition involves the addition of the a-C atom of a carbonyl compound, a carboxylic acid, a carboxylic ester, or a carboxylic amide to the C=0 double bond of an aldehyde or a ketone. The products of aldol additions are /3-hydroxylcarbonyl compounds (aldols), /i-hydroxycarboxylic acids, /Thydroxycarboxylic esters, or j3-hydroxycarboxylic amides. 

Titanium chelates are formed from tetraalkyl titanates or halides and bi- or polydentate ligands. One of the functional groups is usually alcoholic or enolic hydroxyl, which interchanges with an alkoxy group, RO, on titanium to liberate ROH. If the second function is hydroxyl or carboxyl, it may react similarly. Diols and polyols, CC-hydroxycarboxylic acids and oxalic acid are all examples of this type. P-Keto esters, P-diketones, and alkanolamines are also excellent chelating ligands for titanium. 

Mesocyclic lactones. Cyclization of w-hydroxycarboxylic acids via the 0,0 -disilyl intermediates is applicable to medium-sized rings (7-membered, 35% 8- to 13-membered, 79-88%). An initial silyl carboxylate formation step is catalyzed by (Ph3P)3RhCl at room temperature which is followed by an intramolecular 0-silylation at 80°. Elimination of l,l,3,3-tetramethylbenzo-2,l,3-oxadisilazole occurs when the cyclic silylether/esters are exposed to MejSiiOTf). ... 

Synthesis of carboxylic acids from ketones via y -hydroxycarboxylic acid fcrf-butyl esters Modified Reformatskii synthesis... 

As far as the volumetric properties are concerned, values at 25°C have been reported for alcohols(31,55-59a), ethers(11b,34, 58,60,61), amines(34,57,62-64), esters(11b,58), ketones(llb,36,58), amides(36,37,63,65), carboxylic acids(62a,b,67), hydroxycarboxylic acids(66c), polycarboxylic acids(66d), polyols(31,42 56,59b), pyri-dines and others unsaturated heterocyclic compounds containing ni-trogen(38), ethylene glycol derivatives(11a,61,68-70), carbohydra-tes(72-74), urea and derivatives(44,74,75) polyamines(76,77a) amino-alcohols and aminoethers(77b), polyethers(6°,61,77c), alkylhalides (61), benzene and derivatives(llc,26c), Moreover the behaviour of the functions = f(T) has been studied for alcohols(10,12,55,56) and polyols(12,55,56,68,78), ethers(12) and polyethers(llb,12,68), ketones and esters(11b), ethylene glycol derivatives(11a,68,71,78). Compressibility data at 25°C have been calculated from ultrasonic velocity measurements for ethers(79), amines(62), alcohols(79-82), polyols(79), ethylene glycol derivatives(68,71), polyethers(68,74, 79) urea and derivatives(74), carbohydrates(72,74). Finally some investigations about the influence of various types of non-electrolytes on the temperature of maximum density(82b,83) and the adiabatic compressibility minimum(84) of water are to be remembered. 

Mukaiyama developed l-alkyl-2-halopyridinium salts, which are useful reagents for the preparation of carboxylic esters and lactones in the presence of tertiary amines [22]. After generation of activated onium salts from the corresponding co-hydroxycarboxylic acids, spontaneous lactonization smoothly proceeds to produce various macrolactones. Bartlett first used this lactonization method for the... 

A mixture of phenylacetic acid, benzyl alcohol, and tri-n-butylamine in methylene chloride added under argon to a mixture of l-methyl-2-bromopyridinium iodide and methylene chloride, and refluxed 3 hrs. benzyl phenylacetate. Y 97%. F. e., also with l-methyl-2-chloropyridinium iodide, s. T. Mukaiyama et al., Chem. Lett. 1975, 1045 Bull. Chem. Soc. Japan 50, 1863 (1977) carboxylic acid amides from amines (cf. Synth. Meth. 26, 367) s. ibid. 1975, 1163 3,4-dihydro-2H-pyrido-[1,2-a]pyrimid-2-one as acid scavenger cf. ibid. 1976, 13, 57 lactones from hydroxycarboxylic acids (cf. Synth. Meth. 17, 320) with 2-chloropyridine methio-dide and triethylamine s. ibid. 1976, 49 esters with 2 halogeno-3-ethylbenzothia-zolium salts of ibid. 1976, 267 2-chloro-N-methylbenzothiazolium triflate as condensing agent s. F. Souto-Bachiller, G. S. Bates, and S. Masamune, Chem. Com-mun. 1976, 719. 

Diols from lactones via hydroxycarboxylic acids s. 11, 113 Alcohols from carboxylic acid esters GOOR GH2OH... 

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