The reaction of O-methyl thiocarboxylates 8a, b with organic azides at 110
degreesC yielded the corresponding imidates of type 9, which were easily hy
drolyzed to give amides 10. The formation of 9 can be rationalized by a 1,3
-dipolar cycloaddition of the azide with the C=S group, followed by the "tw
ofold extrusion" of N-2 and S. The analogous reaction with methyl dithioben
zoate (11) led to thioimidates 13. On heating, the latter were transformed
into thioamides 12.