CYCLOADDITION REACTIONS OF CYCLOPROPENONE WITH 1,2,4-TRIAZINES, A NEWSYNTHESIS OF PYRAZOLO[1,2-A]1,2,4-TRIAZIN-6-ONES

Contrary to cycloaddition reactions of cyclopropene, 3,3-dimethoxycycl opropene, and 1,2-diphenylcyclopropenone the unsubstituted cyclopropen one reacts regioselectively with the N=N-bond of various 1,2,4-triazin es to yield novel pyrazolo[1,2-a]1,2,4-triazin-6-ones in fair yields. The crystal structure of the pyrazolo[1,2-a]1,2,4-triazine 11 has been determined by X-ray diffraction.