MEISENHEIMER-TYPE COMPOUNDS FROM HETEROAROMATIC SUBSTRATES . REACTION OF METHOXIDE ION WITH 3,5-DINITRO-2-METHOXYPYRIDINE IN METHANOL AND DIMETHYL SULFOXIDE-METHANOL MIXTURES

The interaction between 3,5-dinitro-2-methoxypyridine and sodium methoxide in methanol and dimethyl sulfoxide-methanol mixtures is investigated by visible and nmr spectral measurements. A Meisenheimer-type adduct, the 2-aza-1,3-dimethoxy-4,6-dinitrocyclohexadienate ion (VI), is rapidly formed and is fairly stable in DMSO solution, the equilibrium constant in methanol being 1.9 M−1 at 20°. The data are consistent with a compound resulting from the attack of the methoxide ion on a CH ring position. Structure VI is conclusively established by the aid of a deuterated starting substrate. Methanol promotes the demethylation of the substrate, probably by an Sn2 process, to yield the sodium salt of 3,5-dinitro-2-hydroxypyridine. © 1969, American Chemical Society. All rights reserved.