Aromatic compounds, diamino, oxidation

Some reactions of 2,2 -bipyridine /V-oxides have been reported. The l,T-dioxide is nitrated readily to 4,4 -dinitro-2,2 -bipyridine 1,T-dioxide. ° ° °" 2,2 -Bipyridine 1-oxide is also nitrated in the 4 position. The nitro groups in 4,4 -dinitro-2,2 -bipyridine l,T-dioxide are reactive, being replaced by chlorine with concentrated hydrochloric acid," by bromine with acetyl bromide, by hydroxyl with dilute sulfuric acid, and by alkoxy groups with sodium alkoxides. Some of the dialkoxy derivatives are useful catalysts for the oxidation of aromatic compounds. The dinitro dioxide is deoxygenated to 4,4 -dinitro-2,2 -bipyridine with phosphorus trichloride in chloroform, and other substituted l,T-dioxides behave similarly, but with phosphorus trichloride alone, 4,4 -dichloro-2,2 -bipyridine results. The dinitro dioxide is reduced by iron powder in acetic acid to 4,4 -diamino-2,2 -bipyridine, whereas 4,4 -dichloro-2,2 -bipyridine l,T-dioxide is converted to its 4,4 -diamino analogs with amines. Related reactions have been described. ... 

Several other examples of the oxidation of hydroxyamino and diamino aromatic compounds with silver oxide [368, lead dioxide [368], lead tetraacetate [441], and sodium hypochlorite [694] are documented in equations 534-536. 

Azole approach. 3,4-Diamino-l,2,5-thiadiazole reacts with 1,2-dicarbonyl compounds to form pyrazines (747) (76JHC13). From the reaction of 1,2,5-thiadiazole 1,1-oxides such as (748) with o-phenylenediamine, the l,3-dihydro[l,2,5]thiadiazolo[3,4-Z>]quinoxaline 2,2-dioxide (749) is formed. To understand this reaction it is pointed out that the 1,2,5-thiadiazole 1,1-dioxide ring is to be regarded as alicyclic rather than aromatic and is strongly 7r-electron deficient. Substituents with leaving properties in the 3,4-positions are therefore readily displaced as in the reaction of (748) (75JOC2743). 

Synthetic approaches to 1,5-benzodiazepines and related fused diazepines are frequently accomplished by condensing o-diamino>derivatives of aromatic rings with alkenones, alkynones, jff-diketones, /S-keto-esters, etc, or by intramolecular cyclization of appropriate derivatives of the u-diamino-compounds. Condensations with alkenones are exemplified this year by the reaction of the diamino-uracil (230) with mesityl oxide (or two moles of... 

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