Spiroheterocycles from the reaction of arylnitrile oxides with some (Z)-3-arylidene -2 (3H)-benzofuranones. new access to orthohydroxyphenylisoxazoline esters

Some 4-substituted arylnitrile oxides and (Z)-3-arylidene-2(3H)-benzo-furanones undergo 1,3-dipolar cycloaddition reactions to give exclusively spirodihydroisoxazoles. These spiroadducts have be opened to the corresponding ethyl 3,4-diaryl-5-(orthohydroxyphenyl)-4,5-dihydroisoxazoline-5-carboxylates by the action of concentrated hydrochloric acid at reflux in ethanol.