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Structures of the Intermediates Formed in the Ring-Opening Reaction of 2-Chloro-3-nitropyridine

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journal contribution
posted on 19.01.2007, 00:00 by LeRoy W. Haynes, Virginia B. Pett
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.

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