An intramolecular [2 + 3] cycloaddition route to fused 5-heterosubstituted tetrazoles.

[reaction: see text] Fused 5-heterotetrazole ring systems are synthesized in high yield via intramolecular [2 + 3] cycloadditions of organic azides and heteroatom-substituted nitriles. Cyanates, thiocyanates, and cyanamides are all competent dipolarophiles for this reaction. A variety of scaffolds are tolerated when the new enclosed ring is five- or six-membered.