Jump to main content
Jump to site search

Issue 6, 2002
Previous Article Next Article

Reactivity of N-pyridylcarbamates in basic media

Author affiliations

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.

Graphical abstract: Reactivity of N-pyridylcarbamates in basic media

Back to tab navigation

Publication details

The article was received on 11 Jan 2002, accepted on 08 Mar 2002 and first published on 18 Apr 2002


Article type: Paper
DOI: 10.1039/B200445N
Citation: J. Chem. Soc., Perkin Trans. 2, 2002,0, 1162-1165
  •   Request permissions

    Reactivity of N-pyridylcarbamates in basic media

    F. Norberto, S. Santos, D. Silva, P. Hervés, A. S. Miguel and F. Vilela, J. Chem. Soc., Perkin Trans. 2, 2002, 0, 1162
    DOI: 10.1039/B200445N

Search articles by author

Spotlight

Advertisements