1,3-Dipolar Cycloaddition of [(o-Carboran-1-yl)methyl]azide to Alkynes

摘要

The synthesis of heterocyclic systems widely used in synthetic organic chemistry, technology, and medicine has received much attention in recent time [ 1 ]. In the series of icosahedral closo-carboranes, heterocyclic derivatives are the least studied and difficult to obtain. The available methods for preparing the carbo-rane derivatives of heterocyclic compounds consist mainly in the direct introduction of a heterocyclic fragment into the carborane polyhedron. The methods include the cross-coupling of iodocarboranes with appropriate derivatives of heterocyclic compounds [2], the nucleophilic displacement of a halogen atom in heterocycles with carborane copper derivatives [3], or the addition of carboranyllithiums to highly elec-trophilic heterocycles followed by dehydrogenation of intermediates [4]. These methods have a number of synthetic restrictions imposed by the sensitivity of carborane polyhedra toward bases [5] and the availability of the corresponding heterocyclic component. In recent times, the topical problem is to search for the simple and general methods of synthesis of heterocyclic carborane systems. Triazole derivatives are attractive from this viewpoint: the main method for their synthesis is a copper-catalyzed 1,3-dipolar cycloaddition of azides to alkynes [6].