A series of new 1,2-bis(o-haloaryl)ethanones is efficiently prepared and ap
plied to the synthesis of 4,5-bis(o-haloaryl)isoxazoles. Is elation of inte
rmedate hydroxyisoxazolines, which are structurally examined, provides a de
finitive proof for a heterocyclization mechanism based on an amine exchange
process. The isolation and X-ray crystallographic studies of significant s
ide products such as benzamides and triarylpropionitriles are also describe
d.