Annelated 4,5-diazaspiro[2.4]hepta-4,6-diene obtained by [3 + 2] Cycloaddition of Diazocyclopropane to Cyclooctyne

The 1,3-dipolar cycloaddition of diazocyclopropane generated in situ to cyclooctyne at –30 to –25°C afforded highly reactive spiro(9,10-diazabicyclo[6.3.0]undeca-1(8),9-diene-11,1’-cyclopropane) which can add nucleophiles to the azocyclopropane fragment or undergo oligomerization with three-membered ring opening.