Tetracyclo dodeca-4,8,11-triene

The cycloadditions of 4-mcthyl-3//-1,2,4-triazole-3,5(4//)-dione to tricyclo[5.2.2.02 6]-undeca-2,5,8-triene 37, tetracyclo[5.3.2.02,6.08 1°]dodeca-2,5,ll-triene, and -2,5-diene 39 have been examined107,115. Complete diastereoselectivity was observed only for the trienc derivatives 37 the structure of the adducts 38 was determined by X-ray. 

At 120°C, tetracyclo[5.5.0.0. " 0 ]dodeca-5,8,l 1-triene gives pentacyclo [5.5.0.0. 0. 0 ]dodeca-4,10-diene presumably via an allowed 3,3-sigmatropic shift. Both isomers give benzene above 160°C, and it was suggested that the pentacyclo material reverts to the tetracyclo compound, which undergoes a retro Diels-Alder reaction to bicyclo[6.4.0]dodeca-2,4,6,9,ll-pentaene which is known to give benzene probably by electrocyclization to a tricyclo[6.4.0.0 ]dodeca-3,5,9,ll-tetra-ene, the o,o -benzene dimer, which undergoes the retro 2 + 2 reaction (Scheme 13.9). 

It was noted that tetracyclo[5.3.2.0 0 ]dodeca-3,9,ll-triene gave tricy... 

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