- Nucleophilic acyl substitutions of esters with protic nucleophiles mediated by amphoteric, oxotitanium, and vanadyl species
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(Chemical Equation Presented) A diverse array of oxometallic species were examined as catalysts in nucleophilic acyl substitution (NAS) reactions of methyl (or ethyl) esters with protic nucleophiles. Among them, oxotitanium acetylacetonate (TiO(acac)2) and vanadyl chloride (VOCl 2-(THF)x) served as the most efficient and water-tolerant catalysts. Transesterifications of methyl and/or ethyl esters with functionalized (including acid- or base-sensitive) 1° and 2° alcohols can be carried out chemoselectively in refluxed toluene or xylene in a 1:1 substrate stoichiometry using 1 mol % catalyst loading. The resultant products were furnished in 85-100% yields by simple aqueous workup to remove water-soluble catalysts. The new NAS protocol is also amenable to amines and thiols in 74-91% yields, albeit with higher loading (2.5 equiv) of protic nucleophiles. Representative examples of commercial interests such as Padimate O and antioxidant additives for plastics were also examined to demonstrate their practical applications. A 1:1 adduct between TiO(acac)2 and a given 1-octadecanol was identified as (C18H37O) 2Ti(acac)2 and was responsible for its subsequent NAS of methyl esters.
- Chen, Chien-Tien,Kuo, Jen-Huang,Ku, Cheng-Hsiu,Weng, Shiue-Shien,Liu, Cheng-Yuan
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p. 1328 - 1339
(2007/10/03)
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- 4-Hydroxy-3,5-di-alkyl-phenyl-propionic acid composition suitable as lipid lowering and anti-diabetic agents
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Pharmaceutical compositions acting on the metabolism which contain as active derivatives of the 4-hydroxy-3,5-di-akylphenyl-propionic acid corresponding to the formula I and II EQU1 wherein R1 and R2 which may be identical or different, each stands for an alkylradical having 1 to 8 carbon atoms, R3 stands for an alkylene radical having 2 to 12 carbon atoms, X stands for hydroxy, alkoxy having 1 to 18 carbon atoms, phenalkoxy having 1 to 4 alkyl carbon atoms, cycloalkoxy having 5 to 8 carbon atoms, --NR4 R5 in which R4 stands for an alkyl group having 1 to 18 carbon atoms, R5 stands for a hydrogen atom or R4 and R5 may form with the nitrogen atom a heterocyclic six-membered ring which may carry another hetero atom and n is an integer from 2 to 4 and process for preparing them.
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