| Abstract: | The course of the thermal ring-opening and recyclization of 2-azidopyridine 1-oxides is radically altered by the presence of a 3-halo substituent. Provided the 6-position is blocked, recyclization leads to a 6-cyano-6-halo-1,2-oxazine which hydrolyzes very readily to the 6H-1,2-oxazin-6-one. The structure of 4-bromo-3-methyl-6H-1,2-oxazin-6-one so obtained was confirmed by single crystal X-ray analysis. If the 6-position is not blocked, the product undergoes a further ring opening to give (Z)-β-cyanoacrylates. |
