Diazonium salts, azole

Some weak electrophilic reagents, which are usually inert toward azoles, also react with quaternized azoles. Diazonium salts yield phenylhydrazones (Scheme 48) in a reaction analogous to the Japp-Klingemann transformation of /S-keto esters into phenylhydrazones in the dithiolylium series illustrated the product has bicyclic character. Cyanine dye preparations fall under this heading (see also Section 4.02.1.6.5). Monomethine cyanines are formed by reaction with an iodo quaternary salt, e.g. Scheme 49. Tri- and penta-methinecar-bocyanines (384 n = 1 and 2, respectively) are obtained by the reaction of two molecules of a quaternary salt with one molecule of ethyl orthoformate (384 n = 1) or/S-ethoxyacrolein acetal (384 n =2), respectively. 

N2 Stretching Bands of Diazoazoles and Azole Diazonium Salts... 

All azole diazonium salts and the corresponding diazocompounds can be converted into each other. Thus, neutralization or alkalinization of the... 

Pyridine-2- and -4-diazonium ions are far less stable than benzenediazonium cations. Azole-diazonium salts generally show intermediate stability provided diazotization is carried out in concentrated acid, many of the usual diazonium reactions succeed. Indeed, azolediazonium salts are often very reactive in coupling reactions. 

The coupling of the 4,4,4-trifluoro-l-(thien-2-yl) butane-1,3-dione with azole diazonium salts gives the pyrazolo [5,1-c] triazine (xi), benzimidazo [5-1-c] 1,2,4-triazine (xii) and triazolo [3,3-c] 1,2,4-triazine (xiii) derivatives incorporating trifluoromethyl group [25]. 

The amino-1,3-azoles behave as normal arylamines, for example undergoing carbonyl condensation reactions, easy electrophilic substitutions, and diazoti-sation, though 2-aminooxazoles cannot be diazotised, presumably due to the greater electron-withdrawal by the oxygen. In appropriate cases, good yields of diazoazoles, as opposed to azole-diazoniums salts, can be obtained from aminoimidazoles. ... 

In each table, substituted azoles are ordered in the following way alkyl, substituted alkyl, aryl, formyl, acetyl, carboxylic acid, alkoxycarbonyl, cyano, amino, azido, diazonium salt, nitroso, nitro, hydroxy, alkoxy, fluoro, chloro, bromo, and iodo. 

Isoxazolium salts Trialkyloxonium salt Amidinium salts Ketenimines Diazomethane K-methyldiazotate Hexamethylenetetramine Azo compounds T riazenes p-Nitrobenzene-diazonium sulfate Sulfanilic acid, diazotized HCONH2, CHsC0NH2 Dimethylacylamines HC0N(CHs)2, CHsC0N(CHs)2 1-Benzyl-1,4-dihydro-nicotinamide N,N -Diethylnicotin-amide C0(NH )2, (CHs)2NCON(CHs)2 Phenyl isocyanate Carbodiimides Dicyclohexylcarbodi-imide, Di-p-tolyl-Antipyrine Imidazole 1-Acylimidazole N,N -Carbonyldi( azoles ) N, N -Carbonyldi-imidazole... 

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