Racemisation dynamics of torsion angle restricted biphenyl push-pull cyclophanes
作者:Jürgen Rotzler、Heiko Gsellinger、Markus Neuburger、David Vonlanthen、Daniel Häussinger、Marcel Mayor
DOI:10.1039/c0ob00650e
日期:——
The thermodynamics of the atropisomerisation of torsionangle restricted, axial chiral biphenyl-based push-pull cyclophanes were studied. Using 1H NMR coalescence measurements the rotation barrier around the central C–C bond was determined to be 50 kJ mol−1 for the propyl-bridged biphenyl derivative 1b, displaying only a negligible solvent dependence. By protonation of the piperidinyl nitrogen as electron