Contributions to the Chemistry of N2O and 1-Alkynyltriazenes

This thesis describes the utilization of nitrous oxide N2O as an oxidant in oxidative cou-pling reactions and as a nitrogen atom donor in the synthesis of 1-alkynyltriazene and further reactivity of the latter. An overview of N2O and its reactivity is given in chapter 1. Chapter 2 details attempts and findings made in the use of N2O as an oxidant. In a first part, the optimizations made for the oxidative coupling reaction of sterically demanding Grignard reagents are described. The use of lithium amides resulted in a 1.6-fold improvement of the yields. The use of microwave heating enhanced the reaction, giving access to biaryls with very hindered isopropyl ortho substituents. In a second part, the oxidative coupling of C- and N-nucleophiles mediated by copper is described. The oxidation of organoamidocuprate by N2O gave yields lower than 20%. The results concerning the synthesis and reactivity of 1-alkynyltriazenes are exposed in chapter three, starting with the synthesis of new 1-alkynyltriazene. Aryltriazenes were obtained by using an iodocyclization reaction. The products could be used for further transformation. The cleavage of the triazene moiety by iodine or under acidic condition was successfully made. 1-Alkynyltriazenes were isomerized to 1-allenyltriazenes under basic conditions. These 1-allenyltriazenes were shown to be thermally labile. In presence of zinc, 1-allenyltriazenes rearranged to 1-aminopyrazoles. In certain cases, the based-induced isomerization led directly to the 1,3-dienetriazene. Finally, the gold-catalyzed reaction of 1-alkynyltriazene with imines is shown to selectively form 1,3-diaminopyrazoles in good yield. The reaction is tolerant to a large variety of functional groups on the imine reagent. Dibenzyl-substituted in N3 position pyrazoles were successfully hydrogenated to the amino function yielding 1,3-diaminopyrazoles.