The preparation and novel [3.3] sigmatropic rearrangement of cyclophanes having a spiro skeleton

Abstract

Oxidation of dihydroxy[n.2]metacyclophanes 1 with K₃[Fe(CN)₆] afforded the intramolecular O–C coupling product 2, which has a spiro skeleton in good yield; variable temperature ¹H NMR measurements indicated that compounds 2 are interconvertible by a thermal [3.3] sigmatropic rearrangement, and the activation free energies for the [3.3] sigmatropic rearrangement increased with increasing length of the methylene bridge in compounds 2.