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

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 pK(a) value of 1 was estimated by a titration experiment and ab initio calculations, showing that 1 has a basicity comparable to aniline derivatives.