Diazo-compounds heterocyclic

An obvious alternative route to heterocyclic diazo compounds would be that employed by Doering and De Puy for the synthesis of diazocyclopentadiene. However, attempts to do this have not been very successful.18 

The yellow diazopyrroles have an absorption maximum in the region 320-400 mp (extinction coefficient varying greatly, depending on the other substituents in the pyrrole ring) in their ultraviolet spectra and all show the characteristic diazo peak (2080-2180 cm 1) in their infrared spectra. In general the infrared diazo absorption 

Although a preliminary study of the effect of light on 3-diazo-2,4,5-triphenylpyrrole (21) has been reported, the products of photolysis have not been identified.18a 

There is a report in the literature of the diazotization of ethyl 4-amino-3,5-dimethylpyrrole-2-carboxylate to yield a diazonium salt which couples with alkaline /9-naphthol.l9,20 However, the experi- 

The azo dyes are typical red crystalline compounds those derived from 2-diazopyrroles (40) form lakes with the transition metals.14 

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The aza-transfer reaction between 3-hydrazinopyridazines and aromatic diazonium salts or heterocyclic diazo compounds affords the corresponding tetrazolo[l,5-6]pyridazines, while 3-hydrazinopyridazine 1-oxide gives 3-azidopyridazine 1-oxide (76TL3193, 76X725). 

Tisler and Stanovnik Heterocyclic diazo compounds 80CHE443... 

Diazoindazole (51) is one of the few heterocyclic diazo compounds whose structure has been determined (78AX(B)293). The diazo group shows a substantial carbanionic character (51b). 

A quantitative study of the azo coupling reactions of heterocyclic diazo compounds was made by Sawaguchi et al. (1971), who measured the coupling rates of seventeen heterocyclic diazonium ions with R-acid (2-naphthol-3,6-disulfonic acid) and compared them with those of the benzenediazonium ion with the same coupling component. All the heterocyclic diazonium ions investigated react faster with R-acid than does the benzenediazonium salt. More recently, Diener and Zollinger (1986) confirmed Sawaguchi s results and interpreted them in more detail. 

Weiss and co-workersprepared a series of oxazohnylidene steroids 343 as luminescence dyes for application as potential intracellular diagnostic agents (Scheme 6.72). The key intermediate 2-aryl-5,5-dimethyl-4(57/)-thiooxazolones 341 were readily available from the corresponding 4(57/)-oxazolones 339. Reaction of 341 with 342, generated in situ from the hydrazone 340, gave 343 as expected. It was not possible to prepare 343 from 3-thio-androsta-l,4-dien-17-one since the requisite corresponding heterocyclic diazo compounds could not be prepared. 

Heterocyclic Diazo Compounds J. M. Tedder, Adv. Heterocycl. Chem., 1966, 8, 1-19. 

Utility of Heterocyclic Diazo Compounds in Organic Synthesis M. Tisler and B. Stanovnik, Heterocycles, 1976, 4, 1115-1166. 

The heterocyclic diazo compounds such as diazopyrroles bear the same relation to diazocyclopentadiene that pyridine does to benzene. Just as pyridine is a base and forms a pyridinium ion, in acid solution, so diazopyrroles (5) form pyrrole diazonium salts (6). 

We shall first discuss the preparation of heterocyclic diazo compounds as a class and shall then consider separately the individual characteristics of the various types, e.g., diazopyrroles, diazo-pyrazoles, etc. 

Diazoindazole (11) was first prepared by the diazotization of 3-aminoindazole (9) followed by the treatment of the resulting diazonium salt (10) with base,1,5 This remains the most important method of synthesis for the whole class of heterocyclic diazo compounds. (See p. 4.)... 

Pyrrole and indole diazonium salts are acidic and lose a proton even in dilute acid to yield the diazo compound. Pyrazole diazonium salts, on the other hand, are only feebly acidic and the diazo compound is liberated only in quite strong alkali. In many cases the difficulty in obtaining the heterocyclic diazo compound has mainly centered round the preparation of the preceding amino compound. Nitration... 

One of the factors which stimulated recent interest in heterocyclic diazo compounds was the application of the technique of direct... 

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