Photolytic Rearrangements in Triphenylcyclopropene Systems
Photolysis of 1,2,3-triphenylcyclopropene results in dimerization to 1,2,3,4,5,6-hexaphenyltricyclo[3.1.0.02.4]-hexane. Photolysis of 3-phenyl-, 3-benzyl-, 3-methyl-, and 3-methoxy-1,2,3-triphenylcyclopropene yields no dimeric products. All the compounds rearrange to give some of the corresponding 3-substituted 1,2-diphenylindenes. In addition to indene formation, the 3-methoxy-compound undergoes fragmentation and the 3-benzyl-compound undergoes a benzyl proton shift to form 1,2,3,4- tetraphenylbutadiene isomers. The reaction is postulated to proceed by initial excitement of the cyclopropene .π bond to a π diradical followed by ring opening of the cyclopropene to form a phenyl vinyl carbene which inserts into the 3-phenyl group to form the indene and may undergo other reactions where possible.
J. O. Stoffer and J. T. Bohanon, "Photolytic Rearrangements in Triphenylcyclopropene Systems," Journal of the Chemical Society, Perkin Transactions 2, Royal Society of Chemistry, Jan 1978.
The definitive version is available at https://doi.org/10.1039/P29780000692
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© 1978 Royal Society of Chemistry, All rights reserved.