Imidazole 5- alkoxy-4-nitro

The acylation of the carbanions derived from nitroalkanes with acyl imidazoles or alkoxy-carbonylimidazoles takes place at the carbon atom to yield a-nitro ketones or a-nitro esters, respectively (Eq. 5.10).21 The lithium salts of nitroalkanes were isolated and used in THF or DMSO in the original procedure. Later, potassium salts generated in situ on treatment with r-BuOK in DMSO are reactive enough to give a-nitro ketones in good yield (Eq. 5.11).22... 

Both 1-methyl-4- and l-methyl-5-chloroimidazoles can be nitrated in sulfuric acid. Exhaustive nitration of imidazole in mixed acids yields in succession 4-mono-, 4,5-di-, and 2,4,5-trinitroimidazole. With dinitrogen tetroxide in acetonitrile 4-substituted imidazoles with electron-withdrawing substituents yield a mixture of 5- and 2-nitro derivatives." Nitrations at C-2 are most unexpected. The nitration of 4-(4 -alkoxyphe-nyl)imidazoles with 3-4 M nitric acid occurs ortho to the alkoxy group and in the imidazole 5-position. With concentrated nitric acid di- and trinitro compounds are formed." ... 

Halogens attached to pyrazine react readily with 2>aminopyridine with the formation of a doubly fused imidazole ring. 2-Aminopyridines carrying alkyl or alkoxy groups react at ambient temperature while two halogen atoms or a nitro group inhibit the cyclization. 

---