In a footnote to an article describing various thiazole derivatives, Hofmann2 reported that phosphorus pentachloride reacted vigorously with 2-phenyl-benzothiazole with formation of a crystalline chlorinated derivative, which he did not investigate or identify. We have repeated the experiment and find that Hofmann's product is the 6-chloro-2-phenyl- benzothiazole, since the same product can be obtained from 6-amino-2-phenyl- ...