phosphorus pentachloride
1.N-(2-chloro-phenyl)-N-hydroxyformamide is prepared from o-chl-oronitrobenzene as reduction with formic acid/acetic anhydride . is converted to clonidine by cholorination with thionyl chloride/phosphorus pentachloride and then cycliation with ethye-nediamine. This method siplified the operation and reduced the cost.
