Studies on chalcogen-containing heterocycles. Part 37: m-CPBA oxidation of isotellurochromenes and isoselenochromenes

The oxidation of the 1-unsubstituted isotellurochromenes and isoselenochromenes with m-CPBA resulted in a novel ring-opening reaction to give the o-formyl distyryl ditellurides and diselenides as the sole products in good yields, respectively. The o-benzoyl distyryl ditelluride and diselenide were also produced from the corresponding 1-phenylisochromenes. In contrast, the 1-benzyl and 1-n-butylisochromenes were oxidized to afford the (Z)-1-benzylideneisochromenes and (Z  )-1-butylideneisochromenes under similar conditions; no distyryl compounds were obtained. The distyryl compounds were also obtained by the hydrolysis of the corresponding 2-benzochalcogenopyrylium salts, which were easily converted from the 2-benzoisochromenes by treatment with triphenylcarbenium tetrafluoroborate (Ph3C+BF4−)(Ph3C+BF4−).

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