Triazenes—

Dacarbazine (DTIC-Dome) is metabolized to an active alkylating substance. It is used in the treatment of malignant melanoma and causes myelosuppression. 

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Phenylthiazolo[2.3-e]tetrazole treated with equimolecular amounts of phenyl magnesium bromide gives phenyl(4-phenyl-2-thiazoiyl)triazene (334) (Scheme 191) (620). 

Other amino substituted isoxazoles undergo ring-opening reactions on treatment with base. Thus the amidine derivative (249) gave the triazole (250) (64TL149), while the triazene (251) on reaction with ammonia gave the tetrazole (252) (64X461). 

In the presence of proton-donative organic solvents (alcohols), aliphatic amines do not react with diazonium, whereas aromatic amines form mainly triazenes and also para-aminoazo compounds, which subsequently interact slowly with an excess of diazo reagent via N-coupling and form disazo derivatives. 

In the presence of aprotonic organic solvents, both aromatic and aliphatic amines interact with 4-nitrophenyldiazonium in the same way. The first stage yields fast in corresponding triazenes. At the second stage, irrespective of initial amine nature, triazenes interact with an excess of diazo reagent and fonu l,3-bis(4-nitrophenyl)-triazene. Triazenes of aliphatic amines transform fast as well. In case of aromatic amines, the second stage yield depends on the inductive constants of substituents in an azo component. 

Hetero Diels-Alder reaction of active olefins (enamines) with triazenes, tetrazenes with loss of Nz and formation of new N-heterocycies. 

Protection of primary aryl amines as the triazene is accomplished by diazotiza-tion of the amine followed by reaction with pyrrolidine in aq. KOH. This group is stable to metalation of the aromatic ring by metal halogen exchange. The amine is recovered by reductive cleavage with Ni-Al alloy (aq. KOH, rt, 37-68% yield). ... 

Tire only known example of 1,2,3-triazepine (32) behaves as a reactive cyclic triazene with a high degree of masked diazonium character [74JCS(P1)1248]. 277-1,2,4-Triazepine (33a) has been obtained from the 577-tautomer (33b) by a 1,5-hydrogen shift (74CC45,74TL2303), this being one of these rare cases that an antiaromatic tautomer 33a is more stable than the nonaromatic one 33b. But it must be noted that these 277-1,2,4-tri-... 

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). 

When the 4,4 -dinitroazoxyfurazan 240 reacted with ammonia in anhydrous CHCI3, a mixture of live compounds was formed (Scheme 162) (000HAC48). Compound 241 (59%) was the predominant product. However, the most interesting result of this reaction is the isolation of 3-azido-4-nitrofurazan (3%) and triazene 242 (13%). The formation of these compounds could be explained by reacting the intermediate diazotate generated from the leaving nitrofurazanazoxy moiety with ammonia and with 3-amino-4-nitrofurazan, respectively. 

With primary and secondary aryl amines a reaction at the amino nitrogen can occur, leading to formation of an aryl triazene 5 ... 

Dimtrogen tetroxide is the most versatile of the nitrosating reagents and, in addition, it is readily available. The nitro-soamide method of deamination gives far superior yields and much less skeletal isomerization than the nitrous acid method (which is essentially limited to aqueous media), and it leads to a greater retention of optical activity than the triazene method3... 

Apart from carboxylates, other groups such as carbonate and triazenate (R-NNN-R R = Ph, p-tolyl, etc.) can fulfil the role of bridging ligands in the lantern [102]. 

Other subgroups of alkylating agents are the nitrosoureas (examples carmustine, BCNU lomustine, CCNXJ) and the triazenes (example dacarbazine, DTIC). Platinum derivatives (cisplatin, carboplatin, oxaliplatin) have an action that is analogous to that of alkylating agents (formation of crosslinks) and therefore are appended to this class, as well. 

Transmembrane Signaling Transport ATPase Transporter Transposon Transverse Tubule Triazenes... 

The triazolinyl radical 116 is thermally unstable with a half-life of -20 min at 95 °C. The compound 117 is stable under similar conditions. The decomposition mechanism involves loss of a phenyl radical and formation of a stable aromatic triazene (Scheme 9.26).24 This provides a mechanism for self regulation of the stable radical concentration during polymerization and a supplemental source of initiating radicals. 

Compounds with the classical nonsystematic name diazoamino compound (R-N2NRiR2) and their (logical) derivatives with two or more adjacent nitrogen atoms are considered as substitution products of triazene (NH2 — N=NH), 1-tetrazene, etc. (Rule 942.1). Simple examples are 3-methyltriazene (CH3-NH-N = NH) and 3-methyl-l-tetrazene [NH2-N(CH3)-N = NH]. The classical name is retained only for compounds containing the same group R at each end of an - N=N - NH - group (Rule C-942.2), e. g., A-methyldiazoaminobenzene,... 

At low concentrations of hydrogen ions the diazonium ion formed reacts with the free base of an as yet unattacked amine to produce the triazene (diazoamino) compound. 

Diaminobiphenyl (former name benzidine) can be easily bisdiazotized, but is not cleanly monodiazotized by reaction with one equivalent of a nitrosating agent. However, 4-aminobiphenyl-4,-diazonium ions are formed in a triazene equilibration of a 1 1 mixture of 4,4 -diaminobiphenyl with biphenyl-4,4 -bisdiazonium salts in aqueous HC1 (Tauber, 1894 see also Sec. 13.4). Methods for mono- and bisdiazotiza-tion of 1,4-diaminobenzene (/ -phenylenediamine) have been described by Saunders and Allen (1985, p. 29 see also Sec. 2.2). 

The high reactivity of heterocyclic diazonium ions in azo coupling reactions is the reason why in some cases the primary diazotization products cannot be isolated. For example, diazotization of 2-methyl-5-aminotetrazole (2.14) directly yields the triazene 2.15, i. e., the N-coupling product, since the intermediate diazonium ion is reactive enough to give the N-coupling product with the parent amine even under strongly acidic conditions (Scheme 2-8 Butler and Scott, 1967). 

An interesting example of how the reaction conditions can influence the structure of the product is shown in Scheme 2-10. Depending on the acidity of the reaction medium and on the reaction time, the diazotization of aminotriazoles (2.18) yields the nitrosoamines (2.19), the chloro compounds (2.20), or the azo coupling products i.e., the triazenes (2.21), as shown by Gehlen and Dost (1963). 

The so-called transdiazotizations are mechanistically related to the introduction of diazonio groups using sulfonic acid azides. An aromatic diazonium ion forms a triazene (diazoamino compound) with an aromatic amine the triazene tautomerizes and dissociates at the Na-Np bond of the original diazonium ion. This reaction is important for the synthesis of the 4-aminobiphenyl-4,-diazonium ion, which cannot be obtained by direct (mono-)diazotization of 4,4 -diaminobiphenyl (Allan and... 

Based on observations by Bamberger, Bucherer, and Wolff at the turn of the century, Matrka et al. (1967) described experiments which show that alkaline solutions (pH 8.5-9.2) of substituted benzenediazonium chlorides form nitrite ions and triazenes. The latter is obviously the reaction product of the amine formed in a retro-diazotization with the diazonium ion that is still present. The yield of nitrite formed was between 0.5% (benzenediazonium ion) and 50.2% (2-nitrobenzenediazonium ion). 

As discussed in Sections 5.1-5.3, arenediazonium ions are Lewis acids in which the (3-nitrogen forms the center of electrophilic character. This was demonstrated by the addition of hydroxide ions and water molecules. Other nucleophiles can also be added and, in principle, these reactions display the same mechanistic characteristics as those with OH and H20. According to the nature of the atom of the nucleophile that provides the lone pair of electrons, O-, S-, Se-, N-, P-, or C-coupling can occur. With N- and C-coupling, important and large groups of compounds are formed, namely azo compounds (mainly important as azo dyes) and triazenes, respectively. These compounds will be discussed in Chapters 12 and 13, respectively. 

Ammonia and its inorganic and organic derivatives (HNR R2) couple readily with arenediazonium ions to give triazenes (Ar — N2—NR R2). Originally these compounds were called diazoamino compounds. Nowadays IUPAC nomenclature (IUPAC, 1979, Rule 942.2) recommends that the prefix diazoamino should be used only for compounds with the same organic residue at each end of the — N2 —NH — group. 

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