Structures of the intermediates formed in the ring-opening reaction of 2-chloro-3-nitropyridine.
The reaction of 2-chloro-3-nitropyridine with two equivalents of hydroxide ion was studied by NMR and X-ray crystallography. On the basis of NMR coupling constants, the originally formed ring-opened intermediate is the pseudo-cis form, as predicted by the SN(ANRORC) mechanism. However, the first intermediate is unstable and isomerizes to a second intermediate, which was isolated. The pseudo-trans geometry of the second intermediate [3-pentenenitrile, 2-nitro-5-oxo, ion(-1), sodium] explains why additional base does not lead to the ring-closing reaction as observed with 2-chloro-5-nitropyridine.
Haynes
LeRoy W
LW
Department of Chemistry, The College of Wooster, Wooster, Ohio 44691, USA. haynes@wooster.edu
Pett
Virginia B
VB