Highly effective synthesis of dibromide of (+)-(1R, 2R)-and (-)-(1S, 2S) -1,2- diphenyl-1,2-ethylenediammonium (DPEN∙2HBr) assisted by microwave

Abstract

Abstract:: In this work, the chiral salts (R,R)- and (S,S)-dibromide of 1,2-diphenyl-1,2-ethylenediammonium (R,R)-9 and (S,S)-9 were synthesized, both by conventional and microwave heating, obtaining yields and optical rotations (c 0.43, H2O) of 92%, +17.48° and 90%, -17.50°, respectively (conventional heating by 24 h) and 92%, +17.52° and 89%, -17.44°, respectively (microwave heating by 1.4 h). These compounds were synthesized by means of the racemic intermediate (±)- iso-amarine (±)-6, leading to the separation of their enantiomers, by fractional optical resolution and using as resolution agents the enantiomers of (+)-(S)- and (-)-(R)-MA 3. The starting reagents were benzaldehyde and 28-30% NH4OH, which are economical and commercially affordable. All synthesized compounds were characterized by melting point, solubility, UV-vis, FT-IR (ATR). Imidazoline (±)-6 and salts (R,R)-9 and (S,S)-9 were additionally characterized by 1H and 13C NMR. Polarimetry was determined to (R,R)-(+)-6, (S,S)-(-)-6, (S,R,R)-(+)-7, (R,S,S)-(-)-7, (S,S)-(+)-8, (R,R)-(-)-8, (R,R)-(+)-9 and (S,S)-(-)-9 compounds.