Potential Substituted Amino Groups

V. Compounds with Potential Substituted Amino Groups. , . 417... 

Ultraviolet photoelectron spectroscopy allows the determination of ionization potentials. For thiazole the first experimental measurement using this technique was preformed by Salmona et al. (189) who later studied various alkyl and functional derivatives in the 2-position (190,191). Substitution of an hydrogen atom by an alkyl group destabilizes the first ionization potential, the perturbation being constant for tso-propyl and heavier substituents. Introduction in the 2-position of an amino group strongly destabilizes the first band and only slightly the second. 

Phenazine leucos until now are usually substituted at their 3 and 6 positions by amino groups due to the normal method of synthesis of the parent phenazine dyes. These types of leuco dyes are reactive. An alternative method of dye synthesis allows access to phenazine dyes with just one substituent at the 3-position.20 The resulting leuco dyes are called half diazine leucos. The loss of one exocyclic amino group leads to higher redox potential and results in less reactive leuco dyes, more useful in applications such as thermographic and photothermographic imaging, particularly Color Dry Silver. 

The selective oxidation of the activated aromatic ring, substituted with electron-donating hydroxy or methoxy groups, can be perfomed at relatively low electrode potential (Ep = 0.3-1.2 V vs SCE) and ring closure is the result of the intramolecular nucleophilic attack of an amino group on the oxidized aromatic ring. 

From limited data the generalization has been made that this method fails for the synthesis of 1-substituted dibenzofurans and for the synthesis of 4-substituted dibenzofurans unless the amino group and the potential 4-substituent are in the same ring. These generalizations are not substantiated in the synthesis of polychlorodibenzofurans. Polychloro-2-phenoxy-anilines are poorly soluble and nonbasic so that the usual method is precluded. In these cases aprotic diazotization with isopentyl nitrite in tetrachloroethylene at 80 C is the method of choice. Yields, as determined by GLC, are usually of the order of 40-50%. The yields of pure isolated... 

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