A simple method of synthesis of (±)-2,3-diarylpiperazines and a novel method of resolution of (±)-2,3-diphenylpiperazine

Abstract

Intramolecular reductive coupling of diimines in the presence of Zn/Ti(OiPr)2Cl2 gives the corresponding (±)-2,3-diarylpiperazines in 73-83% yields with dl/meso ratio > 99%: < 1%. The (±)-2,3-diphenylpiperazine obtained in this way was readily resolved partially using L-(+)-tartaric acid, and the enantiomeric purity was enhanced to > 99% ee via preparation of hydrogen-bonded salt aggregates using oxalic acid. © 2006 American Chemical Society.