v-Triazolines-XXII. Cycloaddition reactions of cyclopentadienones to 5-amino-4-methylene-v-triazolines

Tetraphenylcyclopentadienone 2a and 2,5-dimethyl-3,4-diphenylcyclopentadienone 2b were reacted with 5-amino-4-methylene-v-triazolines 1a-c. A single cycloadduct, namely the correspondingly substituted spiro[bicyclo[2.2.1]hept-2-en-7-one[5.4']-1',2',3'-triazole] derivative 3a-c, was formed in all cases. Compounds 3a-c are not stable in solution and rearrange even at room temperature into the corresponding 5-amino-1-aryl-4-[cyclopent-3-en-1-one-2-yl] methyl- 1',2',3'-triazoles 4a-e. The structures of the products are clarified on the basis of spectroscopical data and the reaction pathways are discussed. © 1986.