Reactivity of N-pyridylcarbamates in basic media

Fátima Norberto*, Susana Santos, Daniel Silva, Pablo Hervés, Ana Sofia Miguel, Filipe Vilela

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

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 profile points to an E1cB 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 (Σ−) gives ρ 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 E1cb mechanism of the secondary carbamates by introduction of N, N-disubstitution in the substrate led to a rate-limiting decrease of ca. 106.

Original languageEnglish
Pages (from-to)1162-1165
Number of pages4
JournalJournal of the Chemical Society. Perkin Transactions 2
Volume2
Issue number6
DOIs
Publication statusPublished - 2002

ASJC Scopus subject areas

  • Chemistry(all)

Fingerprint

Dive into the research topics of 'Reactivity of N-pyridylcarbamates in basic media'. Together they form a unique fingerprint.

Cite this