| Publication Type |
Journal Article |
| Title |
Reactivity of N-pyridylcarbamates in basic media |
| Authors |
F Norberto M. Soledade C. S. Santos Daniel Silva P Herves AS Miguel F Vilela |
| Groups |
MET |
| Journal |
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2 |
| Year |
2002 |
| Month |
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| Volume |
|
| Number |
6 |
| Pages |
1162-1165 |
| Abstract |
New secondary aryl N-pyridylcarbamates were prepared by reaction of the aminopyridine anion with aryl chloroformates and their hydrolysis was studied over the pH range from 12 to 13.7. The pH-rate pro le points to an El1cB mechanism, involving pre-equilibrium deprotonation of the nitrogen atom to form an anion that undergoes rate-limiting decomposition into pyridyl isocyanate and a phenoxide ion. Further reaction of the highly reactive isocyanate with water affords N-pyridylcarbamic acid, which spontaneously decomposes to aminopyridine and carbon dioxide. The absence of significant base catalysis and the isolation of a new product resulting from trapping of the intermediate with the base piperidine are also consistent with an elimination-addition mechanism. Finally the observed substituent effect (sigma(-)) gives rho 2.45 which is in accordance with a rate-determining departure of the phenoxide group from the anion intermediate formed in a pre-equilibrium step. Blocking the Elcb mechanism of the secondary carbamates by introduction of N,N-disubstitution in the substrate led to a rate-limiting decrease of ca. 10(6). |
| DOI |
http://dx.doi.org/10.1039/b200445n |
| ISBN |
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| Publisher |
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| Book Title |
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| ISSN |
1472-779X |
| EISSN |
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| Conference Name |
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| Bibtex ID |
ISI:000175760700019 |
| Observations |
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