Cannizzaro’s (C7H6)n conundrum resolved: [1.1.1]orthocyclophane was first made 150 years ago

The product of the reaction of benzyl alcohol with a number of Lewis acids was shown by Cannizzaro in 1854 to have the empirical formula (C7H6)n, and this material has been the subject of much controversy for many decades. Its attribution as an isomer of 1,2,3,4,5,6-hexaphenylcyclohexane is shown to be incorrect, and instead it has been identified as 10,15-dihydro-5H-tribenzo[a,d,g]cyclononene, 3, the parent [1.1.1]orthocyclophane, the X-ray crystal structure of which is reported.

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