1,3-Diyl trapping reaction intermolecular

Leonetti, J. A. Gross, T. Little, R. D. Cycloaddition-fragmentation as a route to bicydic ring systems. Use of the intermolecular diyl trapping reaction./. Org. Chem. 1996, 62, 1787-1793. 

The intermolecular diyl trapping reaction provides a direct and simple route to the linearly fused tricyclopentanoid ring system. As illustrated in the first example of this pathway, heating the dimethyl diazene 9 to 70-75 °C in the presence of an excess of cyclopentenone afforded a 90-98% yield of cycloadducts 10-12 [4].Unfortunately, the process displayed... 

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