Synthesis of Enantiomerically Pure (R,R)- and (S,S)-1,2-Bis(pentafluorophenyl)ethane-1,2-diamine and Evaluation of the pKa Value by Ab Initio Calculations

Abstract 1,2-Bis(pentafluorophenyl)ethane-1,2-diamine (1) was synthesized by the imino pinacol coupling of 4-methoxy-N-(pentafluorobenzylidene)benzylamine using a Zn–Cu couple and p-TsOH·H2O. The optical resolution of (±)-1 by means of chiral HPLC gave enantiomerically pure (R,R)- and (S,S)-1. The pKa value of 1 was estimated by a titration experiment and ab initio calculations, showing that 1 has a basicity comparable to aniline derivatives.