Normal Prismanes

Diphenylcyclopropenone undergoes bimolecular reduction by the action of aluminium amalgam or magnesium-magnesium iodide the product is not, however, the expected pinacol but tetraphenyl-resorcinol [116], It was suggested that a radical anion is the first reduction product and that this then dimerises, as in normal pinacol reductions, but that the dimerisation product rearranges, first to a prismane derivative, then to a bicyclohexadiene derivative, and finally into the resorcinol derivative. 

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