Syntheses for 2-hydroxy-2H-1,4-benzothiazin-3(4H)-one derivatives as thio analogues of natural hemiacetals

Reductive cyclizations of methyl 2-(2-nitrophenylthio)acetate 2 by means of electrochemistry or by catalytic hydrogenation have been used as key steps in the syntheses of the hemiacetals 2-hydroxy-2H-1,4-benzothiazin-3(4H)-one 10 and its 4-hydroxy derivative 9 representing thio analogues of allelo chemicals found in Gramineae and Acanthaceae. In contrast to its natural counterpart 2,4-dihydroxy-2H-1,4-benzoxa-zin-3(4H)-one hydroxamic acid 9 did not undergo degradation by extrusion of formic acid.