Mechanism of esterification of 1,3-dimethylamino alcohols by N-acetylimidazole in acetonitrile and the influence of alkyl and geminal dialkyl substitution upon the rate

Journal of the Chemical Society. Perkin Transactions 2

Volumn , Issue 12, 1997, Pages 2787-2793

  Madder, Annemieke ^a   Sebastian, Sonny ^a   Van Haver, Dirk ^a   De Clercq, Pierre J ^a   Maskill, Howard ^b  

^a GHENT UNIVERSITY   (Belgium)

^b NEWCASTLE UNIVERSITY   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0002621421     PISSN: 03009580     EISSN: None     Source Type: Journal    
DOI: 10.1039/a608488e     Document Type: Article

References (30)

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28. The intramolecular GAC pathway from the zwitterionic tetrahedral intermediate formed from acetylimidazole (which was ruled out by the calculation of strain involved in the proton transfer to N-3 of the imidazole residue) should be much easier for the zwitterionic tetrahedral intermediate formed from acetylpyrazole as this involves intramolecular proton transfer to the more accessible N-2 of the pyrazole residue via a less strained transition structure. Furthermore, since pyrazole is a much weaker base than imidazole, it should be a better nucleofuge, so acetylpyrazole will be more reactive in these reactions if the second step is rate limiting. We have shown, however, that acetylpyrazole is actually less reactive than acetylimidazole with various amino alcohols. We take this as further evidence that the initial intramolecular GBC nucleophilic attack of the amino alcohol is rate limiting.
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30. A. Madder, unpublished results.