Source:http://linkedlifedata.com/resource/pubmed/id/16468795
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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
4
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| pubmed:dateCreated |
2006-2-10
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| pubmed:abstractText |
In the presence of NaY faujasite, the reactions of dimethyl carbonate (DMC) with several ambident nucleophiles such as o- and p-mercaptophenols (1a,b), o- and p-mercaptobenzoic acids (2a,b), o- and p-hydroxybenzoic acids (3a,b), mandelic and phenyllactic acids (4, 5), have been explored under batch conditions. Highly chemoselective reactions can be performed: at 150 degrees C, compounds 1 and 2 undergo only a S-methylation reaction, without affecting OH and CO2H groups; at 165 degrees C, acids 3-5 form the corresponding methyl esters, while both their aromatic and aliphatic OH substituents are fully preserved from methylation and/or transesterification processes. Typical selectivities are of 90-98% and isolated yields of products (S-methyl derivatives and methyl esters, respectively) are in the range of 85-96%. A comparative study with K2CO3 as a catalyst is also reported. Although the base (K2CO3) turns out to be more active than the zeolite, the chemoselectivity is elusive: compounds 2a,b undergo simultaneous S-methylation and esterification reactions, and acids 3-5 yield complex mixtures of products of O-methylation, O-methoxycarbonylation, and esterification of their OH and CO2H groups, respectively. Overall, the combined use of a nontoxic reagent/solvent (DMC) and a safe promoter (NaY) imparts a genuine ecofriendly nature to the investigated synthesis.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:status |
PubMed-not-MEDLINE
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| pubmed:month |
Feb
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| pubmed:issn |
0022-3263
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| pubmed:author | |
| pubmed:issnType |
Print
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| pubmed:day |
17
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| pubmed:volume |
71
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| pubmed:owner |
NLM
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| pubmed:authorsComplete |
Y
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| pubmed:pagination |
1464-70
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| pubmed:year |
2006
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| pubmed:articleTitle |
Highly chemoselective methylation and esterification reactions with dimethyl carbonate in the presence of NaY faujasite. The case of mercaptophenols, mercaptobenzoic acids, and carboxylic acids bearing OH substituents.
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| pubmed:affiliation |
Dipartimento di Scienze Ambientali dell'Università Ca' Foscari, and Consorzio Interuniversitario La Chimica per l'Ambiente (INCA), UdR di Venezia, Calle Larga S. Marta, 2137-30123 Venezia, Italy. selva@unive.it
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| pubmed:publicationType |
Journal Article
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