Synthesis of stable isotopes of auxinic herbicides 4-amino-3,5,6-trichloropicolinic acid and 4-amino-3,6-dichloropicolinic acid
作者:Peter L. Johnson、Norman R. Pearson、Bert Schuster、Jeremy Cobb
DOI:10.1002/jlcr.1613
日期:2009.7
Pentachloropyridine serves as a key intermediate in the synthesis of 4-amino-3,5,6-trichloropicolinic acid (picloram) and 4-amino-3,6-dichloropicolinic acid (aminopyralid). An M+3 stable isotope of pentachloropyridine (1, pentachloropyridine-1-15N-2,6-13C2) was prepared from K13C15N. Isotopically labeled pentachloropyridine was then carried through a seven-step synthesis to give an M+3 stable isotope of 4-amino-3,5,6-trichloropicolinic acid (2, picloram-1-15N-2,6-13C2) in an overall yield of 42%. The chlorine atom in the 5-position of 2 was selectively removed via electrochemical reduction. Carrying out the electrochemical reduction in water provided an M+3 stable isotope of 4-amino-3,6-dichloropicolinic acid (3, aminopyralid-1-15N-2,6-13C2), whereas conducting the reduction in deuterium oxide produced an M+4 stable isotope (4, aminopyralid-1-15N-2,6-13C2-5-2H). Copyright © 2009 John Wiley & Sons, Ltd.
五氯吡啶是合成4-氨基-3,5,6-三氯吡啶酸(毒莠定)和4-氨基-3,6-二氯吡啶酸(氨吡啶酸)的关键中间体。五氯吡啶的M+3稳定同位素(1,五氯吡啶-1-15N-2,6-13C2)由K13C15N制备。然后,通过七步合成,得到同位素标记的五氯吡啶的M+3稳定同位素(2,毒莠定-1-15N-2,6-13C2),总产率为42%。通过电化学还原,选择性去除2中5位上的氯原子。在水中进行电化学还原,得到4-氨基-3,6-二氯吡啶酸的M+3稳定同位素(3,氨吡啶酸-1-15N-2,6-13C2);而在氧化氘中进行还原,则得到M+4稳定同位素(4,氨吡啶酸-1-15N-2,6-13C2-5-