The Reaction of Nucleophilic Reagents at the β-Position of 3-Bromo-4-nitropyridineN-Oxides

The reactions of 3-bromo-4-nitro-2-R1-6-R2-5-X-pyridine N-oxides (1a:R1=H, R2=Me, X=H; 1b:R1=R2=Me, X=H; 1c: R1=R2=H, X=Br) with diethyl sodiomalonate, ethyl sodiocyanoacetate, and ethyl sodioacetoacetate have been carried out. The treatment of 1a, 1b, and 1c with diethyl sodiomalonate gives 3-[bis(ethoxycarbonyl)methyl]-4-nitro-2-R1-6-R2-5-X-pyridine N-oxides (2a, 2b, and 2c) and 4-[bis(ethoxycarbonyl)methyl]-3,5-dibromopyridine N-oxides (3c). With ethyl sodiocyanoacetate, 3-[cyano(ethoxycarbonyl)methyl]-4-nitro-2-R1-6-R2-pyridine N-oxides (4a and 4b) and 4-[cyano(ethoxycarbonyl)methyl]-3,5-dibromopyridine N-oxide (5c) are obtained. With ethyl sodioacetoacetate, 1a and 1c give 3-[acetyl(ethoxycarbonyl)methyl]-6-methyl-4-nitropyridine N-oxide (6a) and/or 3-ethoxycarbonyl-2-methyl-6-R1-7-X-furo[3,2-c]pyridine N-oxides (7a and 7c), but 1b is unaffected by ethyl sodioacetoacetate under the given conditions. The electronic and steric effects of methyl and bromo groups for the reactions are discussed.