The preparation, and rearrangement in 92 % sulfuric acid, of 4-X-2-nitramino-(I), 2-X-4-nitramino-(2), and 6-X-2-nitramino-pyridines (3) is reported (X = H, Me, MeO, Br, C1, C02H). The product isomer ratios can be explained by differential electronic stabilization of the appropriate a complexes for aromatic nitration and steric effects seem relatively unimportant. Deuteration [3-D in series (I), X = Me] had no effect on the product distribution.
The generality of the
formation of an N,O-diacylhydroxylamine from the oxidation of hydroxamic acids in an inert solvent is confirmed for an
extended range of oxidizing agents. Oxidation of o-alkylhydroxamic
acids with a variety of oxidizing agents yields an ester and small amounts of
the corresponding carboxylic acid. No evidence was obtained for an oxidative
intramolecular cyclization of an O-alkyl-hydroxamic
acid, in cases where this was possible, either in the presence or absence of
ultraviolet irradiation.
Rate data for reactions of
XC6H4CSNMeC6H4Y in methanol at 373
K are presented. The thioamides are less reactive than their oxygen analogues.
Linear Hammett plots were obtained for both series (series A: X = variable, Y =
4?-NO2; series B: X = 4-NO2, Y = variable), with p values
similar to those obtained for related oxyamides. There is a general trend to
higher activation energies but more favourable entropies in the thioamides. The
results are interpreted in terms of rate-determining breakdown of a tetrahedral
intermediate, irrespective of the nature of X and Y.
Rate data for the reaction of a number of benzohydrazonoyl compounds with methoxide ion are reported. The stereochemistry of the products was determined by h.p.l.c. The mechanism of the reactions and the stereochemistry of the products resulting from an addition-elimination mechanism are discussed.
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