An exploration of Suzuki aryl cross coupling chemistry involving [2.2]paracyclophane derivatives

Abstract

Suzuki aryl cross coupling reactions using derivatives of [2.2]paracyclophane were examined. A variety of aryl boronic acids and pinacolate esters were successfully cross coupled with 4-bromo[2.2]paracyclophane under standard Suzuki conditions. Whilst an excellent tolerance for electron donating and withdrawing groups was observed, cross coupling reactions with highly sterically demanding borates (e.g. mesityl) were unsuccessful. The preparation and stability of the previously unreported [2.2]paracyclophanyl-4-boronic acid, -pinacolate ester and -dimethyl ester are described, along with the utility of these systems in Suzuki aryl cross coupling reactions. Application of this methodology led to a dicyclophane containing two [2.2]paracyclophane units separated by a 4–4′connected biphenyl spacer group.