Synthesis of Racemic, Diastereopure, and Enantiopure Carba- or Oxa[5]-, [6]-, [7]-, and -[19]helicene (Di)thiol Derivatives
2020
Abstract
A series of carba- or oxa[5]-, [6]-, [7]-, and -[19]helicene (di)thiols was prepared. The Miyazaki-Newman-Kwart rearrangement of (dimethylcarbamothioyl)oxy (oxa)-helicenes in a flow reactor or nucleophilic substitution of dichloro (oxa)-helicenes with alkanethiolates were used in the sulfanylation step.
Despite the high temperatures employed in this key step, no conformational scrambling was observed during the asymmetric synthesis of the diastereo- and enantiopure oxahelicenes. Single-molecule conductivity of the derivative was studied by the scanning tunneling microscopy break-junction method.