Abstract
Long‐range couplings were observed between H‐4 and 2‐CCHa of 2,4‐disubstituted‐5(4H)‐oxazolones, and H‐4 and H‐2 of 4‐alkyl‐5(4H)‐oxazolones. In the presence of triethylamine, H‐4 of the latter migrates to C‐2 accompanied by a shift of the double bond to give 4‐alkyl‐5(2H)‐oxazolones which show 5J coupling between H2‐2 and 4‐CCHa protons.