By diazo coupling

Diethylamino-4-methy]-5 -phenyiazao selenazole, preparation, by diazo coupling, 246... 

Nearly all (extranuclear) hydrazonoquinoxalines are made by treatment of quinoxaline aldehydes, ketones, or their acetals with hydrazine or substituted hydrazine, but a few are produced by diazo coupling. These reactions are illustrated by the following examples. 

Nitrite is determined by diazo-coupling with sulfanilamide and NEDA (see below for full name), forming a reddish color that can be determined with a visible spectrophotometer. 

In 1924 the German company Kalle Co. in Wiesbaden began production of blueprint paper, i.e. a diazo reprographic paper. In that process a sheet coated with a diazonium compound was exposed to an optical image and developed by diazo coupling using a mono-... 

Many of the 3-hydroxytriazene derivatives produced by diazo-coupling onto N-alkyl or A-aryl hydroxylamines decompose explosively above their m.p.s. However, the heavy metal derivatives are stable and used in analytical chemistry. 

An even more serious disadvantage of this technique is that it often impairs the biological activity of the modified protein. The activities of hen s egg lysozyme (EC 3.2.1.17) and alpha amylase from Aspergillus oryzae (EC 3.2.1.1) were lessened by diazo coupling of glycosides or aniline.12 Whether the decrease in activity was due to the modification of critical residues, or to the introduction of aromatic structures, is not yet clear however, enzymes subjected to the diazocoupling conditions in the absence of the diazonium salts retained their activity, implying that the reaction conditions themselves were not responsible for the loss of activity. 

Modification reactions that neutralize charges or introduce hydro-phobic residues usually lower the enzymic activity. The attachment of monosaccharides to alpha amylase by diazo coupling lowered the activity.12 This enzyme was stable to the reaction conditions for diazo coupling (pH 10,15 min at 0°) if the diazonium salts were not included in the solution. Inclusion of maltose in the reaction mixture to protect the active site lessened, but did not eliminate, the loss of activity, suggesting that the incorporation of hydrophobic structures, or the modification of a critical residue distant from the active site, was at least partly responsible for the loss of activity. 

Azirines, reaction with isothiocyanates, 15 Azo dye, 156-168. See also Dyes Azothiazoles, 105, 153, 170, 271-274 analytical applications, 107 by diazo coupling, 105 dyes, 107 IR spectra of, 107... 

The carbocyclic nucleoside analogs 342-344 were prepared by diazo coupling of (lJ mJ-S-pyrimidylaminomethyl-l -trimethylcyclopentyl-methanol (339) with 4-chlorobenzenediazonium chloride to give 340, which upon reduction gave the triamine 341. Ring closure of 341 with nitrous acid gave (17 ,c/s)-3-[(5-amino-7-chloro-3//-l,2,3-triazolo[4,5-d]pyrimidin-3-yl)-... 

Azo compounds bring two substituted aromatic rings into conjugation with an azo group, which is a strong chromophore. Therefore, most azo compounds are strongly colored, and they make excellent dyes, known as azo dyes. Many common azo dyes are made by diazo coupling. 

The following have also been described cationic azo-dyes (111), prepared by diazo-coupling and quaternization/ and the effects of alkali and of... 

The autoxidation of hydroxylamine to nitrite also involves a radical chain process (Kono, 1978), and the reaction is carried out at high pH. The assay was originally utilized by Elstner and Heupel (1976) who initiated the autoxidation by O2 generated by the xanthine/xanthine oxidase reaction. Nitrite formation was determined colorimetrically at 530 nm by diazo coupling with a-naphthylamine and superoxide dismutase was found to inhibit end product formation. Kono (1978) developed the assay further by utilizing nitroblue tetrazolium as the... 

Moreover, a number of aminodeoxycellulose were accessible. Water soluble 6-trialkylammonium-6-deoxycellulose could be prepared [56]. Conversion of cellulose tosylate with diamines like 1,4-phenylenediamine yields polymers that can be applied for the immobilization of enzymes by diazo coupling, for example [57]. 

Another example of a non degradable pendant chain system involves the chemical linkage of catecholamines, such as dopamine, to amino-aryloxy side groups by diazo-coupling techniques (Allcock et al, 1983) (Figure 26). 

Compounds containing an azo linkage are most commonly produced by diazo coupling reactions (equation 20) and by oxidation of hydrazines (equation 21) or primary aromatic amines (equation 22). 

Arylaminoketones 18, 482 Arylating agents, iodonium salts as — 17, 269 C-Arylation by diazo coupling 16, 842... 

Pfitzinger synthesis, steric hindrance in — 15, 526 Phase s. Trapping phase Phenanthrene ring by diazo coupling 12, 916... 

In Summary Arenediazonium cations attack activated benzene rings by diazo coupling, a process that furnishes azobenzenes, which are often highly colored. 

---