Nitrile oxide cycloaddition routes to 2‐(isoxazolyl)‐benzoates and 2‐(1,2,4‐oxadiazol‐3‐yl)benzoates

Cycloaddition of aromatic nitrile oxides to methyl o‐vinylbenzoate produced methyl 2‐(3‐aryl‐2‐isoxazolin‐5‐yl)benzoates; the isoxazolines were converted to methyl 2‐(3‐arylisoxazol‐5‐yl)benzoates. Reaction of the nitrile oxide from o‐methoxycarbonylbenzohydroximinoyl chloride (11) with phenylacetylene, styrenes, and aromatic nitriles resulted in methyl 2‐(5‐phenylisoxazol‐3‐yl)benzoate, methyl 2‐(5‐aryl‐2‐isoxazolin‐3‐yl)‐benzoates (15), and methyl 2‐(5‐aryl‐1,2,4‐oxadiazol‐3‐yl)benzoates, respectively. The isoxazolines 15 were converted to the corresponding isoxazoles 16.