Hydrochloric Acid → 2,6-Dichlorobenzoxazole

Participants

Reaction Conditions

Reaction Steps

1 litre of o-dichlorobenzene and 625 g (3 moles) of phosphorus pentachloride are heated to 160° C., then 169.5 g (1 mole) of solid 6-chlorobenzoxazolin-2-one are introduced in small portions over the course of 60 minutes, vigorous evolution of hydrogen chloride occuring for a short time after each portion. The mixture is then stirred for a further 15 minutes at 150°-160° C., and then cooled to 0° C., whereupon the major part of the excess pCl5 crystallises out. The phosphorus pentachloride precipitate is filtered off with suction, Washed with a little cold o-dichlorobenzene, and the filtrate is fractionated under reduced pressure. phosphorus oxychloride distils over first, then o-dichlorobenzene together with the remainder of the excess phosphorus pentachloride, and last, at about 110° C. and 17.3 mbar, 2,6-dichlorobenzoxazole. About 136 g of 2,6-dichlorobenzoxazole of melting point 48-49° C. are obtained. GC purity 99.7%. yield: 72% of theory.

Provenance & Evidence