CHEMISTRY OF ETHANEDIYL S,S-ACETALS .11. NEW SYNTHESIS OF CARBOXIN AND OXYCARBOXIN PESTICIDES - APPLICATION TO THE PREPARATION OF THEIR NEWANALOGS SUBSTITUTED AT THE C-2 METHYL-GROUP

A new synthesis of carboxin 1a and its 4,4-dioxide derivative, oxycarb oxin 2a, has been devised via N-bromosuccinimide-promoted oxidative re arrangement of acetoacetanilide 1,3-oxathiolane 3. The replacement of N-bromosuccinimide with molecular bromine leads to the formation, from compound 3, of a C-2 bromomethylcarboxin derivative 1b. The latter is conveniently exploited to prepare a new class of carboxins and oxycar boxins (after oxidation of the sulfur) substituted at the C-2 methyl, by replacement of the bromine atom with various nucleophiles.