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 .