1-Aryl-3,3-dialkyltriazenes: A Convenient Synthesis from Dry Arenediazonium o-Benzenedisulfonimides - A High Yield Break Down to the Starting Dry Salts and Efficient Conversions to Aryl Iodides, Bromides and Chlorides

Abstract

This research comprises three parts. The first part regards the synthesis of 1-aryl-3,3-dialkyltriazenes 3 by reaction of dry arenediazonium o-benzenedisulfonimides 1, also coming from weakly basic aromatic amines with dimethylamine or diethylamine in aqueous solution at 0-5°C. Yields were usually greater than 90% and there was the possibility of recovering the o-benzenedisulfonimide (5), which could be reused to prepare the salts 1. In the second part it was demonstrated that there is the possibility of reconverting the triazenes 3 into the starting stable dry salts 1 by using 5 as acid. The reactions were carried out in glacial acetic acid at 50-55°C and normally afforded salts 1 in yields of around 90-99%. The third part concerns the setting up of two procedures for the conversion of 3 to aryl iodides 9, bromides 10 and chlorides 11. Procedure A used the corresponding aqueous hydrogen halides in acetonitrile at r.t. or 60°C, sometimes in the presence of aqueous HBF 4 , sometimes Cu powder (25 examples, yields 65%-88%). Procedure B usually used anhydrous methanesulfonic acid and tetraalkylammonium halides in anhydrous acetonitrile at temperatures varying from r.t. to 80°C, sometimes in the presence of Cu (16 examples, yields 65-88%).Triazenes are a class of compounds of great interest. 1 Their biological activity has been and still is, the subject of numerous studies; several triazenes are chemotherapeutic agents active against bacterial and especially, protozoal infections, while the 1-aryl-3,3-dimethyltriazenes possess significant in vivo anti-tumor activity. For example, wide therapeutic use is made of dacarbazine, i.e. 5-(3,3-dimethyltriazeno)imidazole-4-carboxamide, as an active principle against human malignant melanoma. Still in the medical field, triazenes are used in the preparation of radiolabeled materials, used as tracers in diagnostic procedures. In technological applications, the ability of triazenes to break down to yield, in situ, diazonium ions with coupling properties is widely used to produce insoluble azo dyes directly on natural and synthetic fibres. Finally, the triazene group plays a significant role in organic synthesis, being a protected form for both the diazonium group and hence for all the functional groups deriving from it and for the aromatic and aliphatic amines from which it arose.It was within a wider investigation aimed at evaluating the synthetic potential of the dry arenediazonium obenzenedisulfonimides 2 1 that the present research was undertaken, it consists of three parts: i) the setting up, based on the use of dry arenediazonium o-benzenedisulfonimides 1, of a simple synthetic procedure for 1-aryl-3,3-dialkyltriazenes 3, also valid for the preparation of unknown or difficult to obtain compounds; ii) break down of the triazenes 3 to the starting dry salts 1; iii) realisation of efficient procedures for converting, in aqueous or anhydrous organic solvents, the 1-aryl-3,3-dialkyltriazenes 3 into aryl iodides, bromides and chlorides, via the corresponding arenediazonium salt ...

Synthesis of New Donor‐Substituted Biphenyls: Pre‐ligands for Highly Luminescent (C^C^D) Gold(III) Pincer Complexes

“…The triazene 25 decomposes in the presence of HI [55] to the diiodo biphenyl 26 . We identified a variation employing proton exchange resin and sodium iodide, that is, in situ formed HI, in dry acetonitrile to be the most effective [56] .…”

Carbon Networks Based on Dehydrobenzoannulenes. 5. Extension of Two-Dimensional Conjugation in Graphdiyne Nanoarchitectures

“…For the latter step, triazene decomposition with MeI for 24 gave only degradation above 140 °C, whereas below this temperature no reaction occurred. For that reason, several modifications were attempted until we found optimal conversion by reacting the triazene with HI and I 2 at 60 °C for 30 min . A final cross-coupling of 24 and trimethylsilylbutadiyne gave key piece 8 in 34% yield over the five steps.…”

Preparative Fluorous Mixture Synthesis of Diazonium-Functionalized Oligo(phenylene vinylene)s

“…Heating a molecule containing the triazene moiety in iodomethane converts it into an aryl iodide, which provides an active site for further chemistry . A non-reductive acid, such as HOAc or trifluoroacetic acid (TFA), cleaves the same bond formed during synthesis of triazene, giving back the aryl diazonium salt and the amine. , Although there are a few cases in the combinatorial literature of the conversion of triazene groups to synthesize aryl diazonium salts, this conversion was limited to the regeneration of diazonium functionalized resins. , Our work is the first to make aryl diazonium libraries.…”