Alkenyl-substituted azides

A second group of aromatic substitution reactions involves aryl diazonium ions. As for electrophilic aromatic substitution, many of the reactions of aromatic diazonium ions date to the nineteenth century. There have continued to be methodological developments for substitution reactions of diazonium intermediates. These reactions provide routes to aryl halides, cyanides, and azides, phenols, and in some cases to alkenyl derivatives. 

Many new pyridazine, cinnoline, and phthalazine syntheses relied on the use of hydrazine-based precursors. 4,5-Dihydro-3(2//)-pyridazinones were obtained by cyclization of hydrazine with Meldrum s acids <97SC3513>, and six-membered cyclic hydrazides 3 were obtained in very high diastereoselectivities by the coupling of azide-substituted bisfenol silanes) <97JOC5680>. PhSeBr-promoted cyclization of alkenyl phenylhydrazones led to tetrahydro-pyridazines <97T7311>, condensation of furofuranones and hydrazines led to pyrrolo[2,3-... 

We first synthesized suitably functionalized amides in four steps from the corresponding alkenyl bromides (Scheme 11). The allylsilane function was introduced by cross-metathesis between the terminal alkenes and allyltri-methylsilane. Then, the bromide was substituted by an azide and the latter was reduced to the primary amine by the action of LiAlELj. As before, a pep-tidic coupling with vinyl acetic acid led to the desired starting compound with a diastereomeric ratio /Z=70/30. 

Perfluoropropene and perfluorobutene-2 react with benzyl azide at 150 °C to give the [3+2] cycloadducts in 85% and 65% yields, respectively. Trimethylvinylsilane also undergoes the [3+2] cycloaddition reaction with 4-nitrophenyl- and 4-cyanophenyl azide to give the triazolines in high yields. Also, ]V-alkylmaleimides react with trimethylsilyl azide to give the corresponding [3+2] cycloadduct . The reaction of maleimide A -proponic acid and a heterocyclic azide is accelerated by molecular recognition . The palladium-catalyzed reaction of alkenyl bromides with sodium azide in dioxane at 90 °C or DMSO at 110 °C affords the 4-substituted 1,2,3-triazoles 55. ... 

Other reactions of synthetic utility can be observed when suitable nucleophiles are added to the reaction system. Typical examples of these nucleophiles are azide, cyanate, thiocyanate, and cyanide anions and thioanisole. Reactions using these nucleophiles provide a reaction path to functionalized vinyl derivatives. The transformations are successfully achieved by using triaryl-substituted alkenyl halides. The reactions with such nucleophiles provide an efficient path to heterocyclic compounds, among others. Some examples, such as the pyrroHnes, isoxazoHnes, isoquinolones, and thio derivatives, are prepared by this method and are shown in Equation 11.11. 

---