Preparation of optically pure ethyl (R)-(+) and (S)-(-) 2-[4-(6-chloro-2-quinoxalinyloxy) phenoxy] propanoate by resolution method and their herbicidal activities

• Published in: Journal of Pesticide Science 1985-01, Vol.10 (1), p.75-79
• Main Authors: Sakata, G, Makino, K, Kusano, K, Satow, J, Ikai, T, Suzuki, K. (Nissan Chemical Industries Ltd., Tokyo (Japan))
• Format: Article
• Language: English
• Subjects: ACCION DEL PLAGUICIDA; ACTION DES PESTICIDES; APPLICATION METHODS; COMPOSE ORGANOCHLORE; COMPUESTO ORGANICO DEL CLORO; HERBICIDAS; HERBICIDE; HERBICIDES; METHODE D'APPLICATION; METODOS DE APLICACION; OPTICAL PROPERTIES; ORGANOCHLORINE COMPOUNDS; PESTICIDE ACTIONS; PROPIEDADES OPTICAS; PROPRIETE OPTIQUE
• ISSN: 0385-1559; 1348-589X; 1349-0923
• DOI: 10.1584/jpestics.10.75

Optically pure ethyl (R)-(+) and (S)-(-)-2-[4-(6-chloro-2-quinoxalinyloxy) phenoxy] propanoate ((R)-(+)-1 and (S)-(-)-1) were synthesized from the corresponding propanoic acids ((R)-(+)-1-acid and (S)-(-)-1-acid), which were prepared from the racemic compound by optical resolution with cinchonidine and cinchonine. Both (R)-(+) and (S)-(-)-1-acid were converted into the corresponding acyl chlorides followed by the reaction with ethanol in the presence of pyridine to afford optically pure (R)-(+) and (S)-(-)-1, respectively. Optical purity was determined by the measurement of 200MHz NMR spectra using Eu(HFC)3 shift reagent and by the preferential crystallization. It became clear that optically pure (R)-(+)-1 had [α]20D+39.9° (CHCl3, c=1.20%). The growth inhibiting activity against rice plants in petridish and the post-emergence herbicidal activity against Echinochloa crus-galli and Digitaria adscendens were examined. The herbicidal activity was influenced mainly by chiral center at the propanoic acid moiety and the (R)-(+)-isomer was the most active.