Esters hydrogenation

Phosphated and Polyphosphated Alcohols In most cases aliphatic alcohols with a chain length in the range of 10-20 carbon atoms are converted with phosphorus pentoxide. A mixture of alkyl dihydrogen esters (primary) and dialkyl hydrogen esters (secondary) are yielded. 

The 2 proton difference was assumed to be the result of one less double b nd in lib. GC/MS of the methylated mixture produced peaks having M ions of m/e 320 and m/e 322 corresponding to the esters o Ila and lib. GC/MS of the hydrogenated methyl esters produced one M of m/e 326 showing Ila and lib were converted to the same hydrogenated ester. The assumption of a double bond difference in Ila... 

The Ion m/e 171, C.H.,.0, (2 R+D) and those corresponding to the methyl esters ana hydrogenated ester derivatives and the unbroken chain of dloxy Ions to C H O. establish the positions of the hydroxyl group and the double bond. The other half of the compounds, corresponding to m/e 135 and m/e 137, had emperlcal formulas... 

Keto esters are the best functionalized ketone substrates for enan-tioselective hydrogenation. Esters of methyl, primary, secondary, and tertiary alcohols can be used to produce hydroxy esters in high yields, with up to 100% enantioselectivity (Scheme 49) (95). The fact that methyl 2, 2-dimethyl-3-oxobutanoate is hydrogenated in high chemical and optical yields with normal asymmetric orientation implies that the reaction does not necessarily involve the enol. 

Hydroformylation of norbomene proceeds slowly in spite of the expected reactivity of the strained double bond. Racemization of the product aldehyde does not occur under the reaction conditions. The hydroformylation of methyl methacrylate gives only one isomer, which is a useful chiral synthon. Dimethyl itaconate also can be hydroformylated using (12) as the chiral ligand to give aldehyde product in 82% ee accompanied by hydrogenated ester.64... 

The use of a strong base in the palladium-catalyzed amination of aryl halides precludes the use of many substrates, such as those with aromatic nitro groups or enolizable hydrogens, esters other than tert-butyl esters, and many substrates with base-sensitive stereochemistry such as some protected amino acids and heterocyclic substrates [191]. Thus, conditions that employ milder bases are required. A solution that involves reaction temperatures as low as those used for reactions conducted with sodium tert-butoxide has not been developed. However, carbonate and phosphate bases can be used with certain catalysts at reaction temperatures comparable to those of reactions involving the first- and second-generation catalysts. 

The acid-catalyzed equilibrium of a dibasic acid with its mono- and di-esters furnishes a means of preparation of alkyl hydrogen esters of most aliphatic a,o)-dibasic acids. A mixture of the acid and its dialkyl ester is refluxed with concentrated hydrochloric acid and dibutyl ether, and the add ester is isolated by fractional distillation or extraction techniques. Excellent directions are given for the acid esters of adipic, sebacic, and azelaic acids. 

Because they lack the phenolic hydrogen, esters are more stable than free vitamers, but they are not antioxidants in vitro. Tocopheryl esters hydrolyze slowly under, eg., acidic aqueous systems, thus providing antioxidant activity for emulsions, soft drinks and some dairy products (Schuler, 1990). 

Resin acids and Rosin acids, hydrogenated, esters with... 

An important application of hydrogenating ester cleavage is involved in Bergmann s benzyloxycarbonyl method of synthesizing peptides.79 In this an amino acid is treated with benzyl chloroformate and then coupled with another amino acid molecule the benzyl group of the resulting benzyl carbamate residue produced is finally removed as toluene, the carbamic acid derivative that results decomposing immediately to carbon dioxide and the desired peptide ... 

CAS 65997-13-9 EINECS/ELINCS 266-042-9 Synonyms Resin acids and rosin acids, hydrogenated, esters with glycerol Rosin, hydrogenated, glycerol ester Definition Monoester of glycerin and hydrogenated mixed long chain acids derived from rosin... 

Synonyms Glycerides, cottonseed-oil mono, hydrogenated, ester with sulfobutanedioc acid, disodium salt Sulfobutanedioic acid, hydrogenated cottonseed glyceride, disodium salt... 

Although the yield of the dialkyl hydrogen esters can be influenced by the ratio of alcohol to P4O10, in practice, mixtures of primary and secondary esters are obtained always, e.g. changing the molecular ratio of alcohol to P4O10 from 2 1 to 4 1 results in an increase of the secondary ester in the mixture from 35 to 65%. 

Wolfrum L, Pinnow J (1918) Ethyl hydrogen ester citrates. J Praktische Chemie (Leipzig) 97 23-50... 

---