INTRAMOLECULAR CYCLOADDITIONS WITH ISOBENZOFURANS .12. SYNTHESIS AND REACTIONS OF FURO[3,4-D]ISOXAZOLES

The synthesis of furo[3,4-d]isoxazoles (3) and inter- and intramolecul ar cycloaddition reactions (to 4, 5a,b) are reported. The structures o f 3k, 5b and 6 have been clarified by X-ray crystallography. Quantum c hemical calculations (AM1, PM3, ab initio, density functional methods) concerning the geometry and the different reactivity of benzo[c]furan s and furo[3,4-d]isoxazoles were performed.