A carbon‐13 Nmr assignment study of 3,5‐diarylisoxazoles

The assignment of the carbon‐13 nmr resonances of 3‐(aryl)‐5‐phenylisoxazoles (I) and 3‐phenyl‐5‐(aryl)‐isoxazoles (II) in dimethylsulfoxide‐ d 6 has been made. The assignments were made by using model compounds, chemical shift arguments, coupling with fluorine substituents, and shifts resulting from quaternization of the isoxazole ring. A carbon‐13 nmr method for distinguishing between I and II which can be produced simultaneously by certain synthetic methods is presented.