1 ,3-Dipolar species such as nitrile oxides, nitrones, nitrile imines, diazoalkanes, nitrile ylides, and azomethine ylides have shown broad application in organic synthesis as reactive intermediates which undergo [3+2] cycloaddition reactions with appropriate dipolarophiles. These methods furnish quick, efficient access to a variety of five-membered heterocycles. The reactions of such 1,3-dipoles with monomeric terminal imido complexes of transition metals (M=NR), in particular titanium(IV) and zirconium(lV), will be explored. Certain classes of the five-membered azametallacyclic intermediates show promise as versatile entry points to a number of highly-substituted heterocycles. Issues of regiochemistry and the scope of substitution of the dipole and metal complex will be elucidated. In addition, the insertion of 1,3-dipoles into the zirconium-carbon bond of zirconaaziridines also shows potential as a route toward related metallaheterocycles. Since nitrogen-containing heterocycles are such vital moieties in a host of pharmaceuticals today, the methodology addressed in this research will impact the field of medicinal chemistry by expanding the aresenal of tools available for the construction of such compounds.
