Trithiazyl trichloride 1 converts 2,5-disubstituted furans into isothi
azoles (e.g. 3, 6, 7) regiospecifically and in good yield, providing a
new, one-step synthesis of isothiazoles, for which a novel mechanism
involving formation and ring-opening of a beta-thiazylfuran 4 is propo
sed.