Reactions of thioesters with organic azides - A novel access to imidates and thioimidates

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.