Document Detail

Lanthanum(iii) catalysts for highly efficient and chemoselective transesterification.
MedLine Citation:
PMID:  23325290     Owner:  NLM     Status:  Publisher    
A facile, atom-economical, and chemoselective esterification is crucial in modern organic synthesis, particularly in the areas of pharmaceutical, polymer, and material science. However, a truly practical catalytic transesterification of carboxylic esters with various alcohols has not yet been well established, since, with many conventional catalysts, the substrates are limited to 1°- and cyclic 2°-alcohols. In sharp contrast, if we take advantage of the high catalytic activities of La(Oi-Pr)(3), La(OTf)(3), and La(NO(3))(3) as ligand-free catalysts, ligand-assisted or additive-enhanced lanthanum(iii) catalysts can be highly effective acid-base combined catalysts in transesterification. A highly active dinuclear La(iii) catalyst, which is prepared in situ from lanthanum(iii) isopropoxide and 2-(2-methoxyethoxy)ethanol, is effective for the practical transesterification of methyl carboxylates, ethyl acetate, weakly reactive dimethyl carbonate, and much less-reactive methyl carbamates with 1°-, 2°-, and 3°-alcohols. As the second generation, nearly neutral "lanthanum(iii) nitrate alkoxide", namely La(OR)(m)(NO(3))(3-m), has been developed. This catalyst is prepared in situ from inexpensive, stable, low-toxic lanthanum(iii) nitrate hydrate and methyltrioctylphosphonium methyl carbonate, and is highly useful in the non-epimerized transesterification of α-substituted chiral carboxylic esters, even under azeotropic reflux conditions. In these practical La(iii)-catalyzed transesterifications, colorless esters can be obtained in small- to large-scale synthesis without the need for inconvenient work-up or careful purification procedures.
Manabu Hatano; Kazuaki Ishihara
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-17
Journal Detail:
Title:  Chemical communications (Cambridge, England)     Volume:  -     ISSN:  1364-548X     ISO Abbreviation:  Chem. Commun. (Camb.)     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-17     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9610838     Medline TA:  Chem Commun (Camb)     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan.
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