[3 + 3] Cycloaddition Reactions Of α-Acidic Isocyanides With1,3-Dipolar Azomethine Ylides

Isocyanides have proven to be very useful synthetic intermediates due to their unique reactivities, high selectivities and functional group compatibilities. So many reactions on the basis of isocyanides have been reported, including multicomponent reactions, domino reactions(a reaction forming multiple bonds or multiple rings), insertion reactions,cycloaddition reactions and so on.Since the synthesis of five-membered heterocycles based on α-acidic isocyanides was discovered by Sch?llkopf in 1968, the [3+2] cycloaddition reaction of a-metalated isocyanides with activated multiple bonds has become a particularly powerful transformation for the synthesis of a wide range five-membered heterocycles, such as pyrrole, pyrroline,oxazole, oxazoline, imidazole, imidazoline, and thiazole derivatives, etc. However, to our knowledge, the cyclization of α-acidic isocyanides for the synthesis of six-membered heterocycles remains unexplored.In this thesis, we describe the first [3+3] cross cycloaddition of α-acidic isocyanides with 1,3-dipolar azomethine ylides to generate a series of 1, 2, 4-triazine derivatives under mild reaction conditions. This new strategy shows that α-acidic isocyanides can also be taken as the potent reagents for the synthesis of six-membered heterocycles.