Thermal cyclisation of 2-nitrophenyl-and 3-nitrohetaryl-ethanoate derivatives in xylene is facilitated indirectly by 5 Å molecular sieves affording an efficient general method for the construction of synthetically useful 3, 4-fused isoxazoles; evidence for the mechanism of these novel heterocyclisation reactions is presented.
![ethyl benzo[c]isoxazole-3-carboxylate Structure](https://image.chemsrc.com/caspic/479/90924-33-7.png)
