| Abstract
| - Synthesis of 8,16-dicyano-anti-[2.2]metacyclophane-1,9-diene, 1b, was achieved in five steps from 1,3-bis(bromomethyl)benzonitrile. Unlike most metacyclophanedienes which easily thermally isomerize (τ1/2= minutes to days at 20 °C) to dihydropyrenes 2, dinitrile 1b shows no tendency to convert thermallyto 2b at room temperature (τ1/2> 30 years), consistent with predictions based on calculation of activationbarriers. Irradiation of cyclophanediene 1b with UV light readily forms the dinitriledihydropyrene 2b,which unexpectedly shows a much more facile (50 °C) 1,5-sigmatropic rearrangement of the internalnitrile groups to give dihydropyrenes 9b and then 10b than is the case for internal methyl substituents,2a, which forms 9a at temperatures above 190 °C. Synthesis of the 2-formyl derivative 1c and the2-naphthoyl derivative 1d are also described. These substituents were predicted to lower the activationbarrier for the thermal closing reaction to the corresponding dihydropyrenes, and experimental evidencesupports these calculations.
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