Triazenes derivatives

Dilution of a solution of diazonium salts in sulfuric acid with water affords triazene derivatives (95IZV1315,95RCB1269). Treatment of a bridged bis(amino) furazans 200 with nitrous acid in acetic or hydrochloric acid gives macrocyclic triazene 201 (Scheme 132) (95MI4). 

Aliphatic primary and secondary amines primarily react with the diazonium compound fast black salt K to yield colored triazene derivatives [1] according to the following scheme ... 

To this end, the diazoimidazole carboxamide compound 32 was transformed first by methylamine to the methyl-triazene derivative 39, which was reacted with 11 (". -phosgene to give the desired product 40 <2002JME5448>. In another approach, 32 was directly cyclized to the bicyclic product by using 1 C-labeled methyl isocyanate. This route allowed the synthesis of both the C-2-labeled 40 and the (7-methyl-labeled samples 41 <1997JLR371, 2002JME5448> (Scheme 13). 

As we have already seen in the case of aniline, primary aromatic amines do not couple normally a triazene derivative, diazoamino-benzene, is produced by linkage through the NH2-group just as in the case of aliphatic amines, e.g. dimethylamine ... 

Care is required with these compounds since many explode on heating [1], A number of triazene derivatives bearing hydrogen, or cyano, hydroxy or nitroso groups on the terminal nitrogen of the chain are unstable, mainly to heat [2], Purification of triazenes by vacuum sublimation carries the risk of explosion [3], Further examples of unstable triazenes and precautions are given [4,5], Individually indexed compounds are ... 

Magnesiated triazene derivatives like 96 can further be used for the preparation of functionalized carbazoles 97 (equation... 

Resin-bound triazenes with a free NH group can be acylated by treatment with acyl halides, or carbamoylated by treatment with isocyanates [342]. The resulting triazene derivatives are stable towards strong bases, but undergo acidolysis when treated with TFA or TMSC1, yielding amides and ureas, respectively (Entries 1 and 2, Table 3.16). Polystyrene-bound triazenes devoid of a free NH group or carbamates can be cleaved from the support by treatment with acyl halides to yield amides (Entries 3 and 4, Table 3.16). 

Triazenes have been prepared by the treatment of resin-bound aromatic diazonium salts with secondary amines (Figure 3.27). Regeneration of the amine can be effected by mild acidolysis (Entry 1, Table 3.23). Triazenes have been shown to be stable towards bases such as TBAF, potassium hydroxide, or potassium tert-butoxide [454], and under the conditions of the Heck reaction [455]. Primary amines cannot be linked to supports as triazenes because treatment of triazenes such as R-HN-N=N-Ar-Pol with acid leads to the release of aliphatic diazonium salts into solution [373]. Triazenes derived from primary amines can, however, be used for the preparation of amides and ureas (see Section 3.3.4),... 

Convincing evidence that vinyl cations, possibly resulting from diazonium ion precursors, are the actual intermediates of the acid-catalysed decomposition of l-aryl-3-vinyl triazene derivatives 112 (equation 20) has been discussed by Jones and Miller (1967). 

R ently the formation of an unusual triazene derivative 99 was reported in the coupling reaction of skatole 95 (R=CH3) (42) Based on the change of the UV spectrum of the reaction mixture with time, a mechanism involving primary formation of the azo compound 97 followed by the hydrolytic cleavage of the indolenine system and reclosing of the ring to finally give 99 was proposed (42)... 

A dimeric form of SbC NCO (98), stable at low temperatures, has been isolated from a reaction between KSbCl5NCO and SbCls in solution in liquid SO2, but above room temperature the rearrangement to an s-triazene derivative (99) has been confirmed by an X-ray study. A new heterocycle (100) has been synthesized by the action of water on the formamidinium salt [C1C(0)N-MeCClNMeC(0)Cl] SbCle, which is the initial product when SbCls and methyl isocyanate are refluxed in carbon tetrachloride. ... 

In the presence of O, NO shows sufficiently high reactivity in reactions with nitrogen-containing organic compounds. It has been found that primary aromatic amine reacted with NO + O in benzene to give triazene derivatives in 60-64% yield [32]. The proposed reaction mechanism includes the formation of intermediate N-nitroso compounds in reaction with dimers of NO ... 

In benzene, the reaction pathway connected with the H-atom abstraction from solvent molecules is not realised, and triazene derivatives are mainly formed in similar conditions. The reaction of NO with secondary and tertiary amines in the presence of oxygen gives N-nitrosamines as the main products [34]. These compounds cannot apparently isomerise into oximes similar to reaction (Equation 3.28) and are stabilised. 

Standard condensation procedures have been used to prepare /S-D-ribofuranosyl derivatives of 5-fluoro-6-methyluracil, fluorine-substituted 4-amino -2(IH)-pyridones, various pyridazinones, as-triazene derivatives of type (1), 4-substituted-3-hydroxypyrazoles... 

Triazene derivatives also continue to receive attention as potential antlneoplastic agents, based on the encou gi antitumor activity of 5-(3,3-dimethyl-l-triazenc imidazole-4-cart)oxamide in man. The compounds 4-carbethoxy-5 (3,3-dimethyl-l-triazlno)-2-phenylimidazole, and the corresponding 2-methylimidazole derivative pcil) showed activity against various experimental rodents tumors com-... 

Cycloheptatriene reacts with DAD to afford exclusively ene products, as do the enols of some triazene derivatives. Allenes with alkyl substituents react with DAD to yield ene products in most cases (eq 7). Ene reactions with DAD have also been found to be a useful way of cleaving allyl ethers. ... 

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