Ring transformations in reactions of heterocyclic halogeno compounds with nucleophiles (XXXIV): Ring contraction of 4‐chloropyrimidine‐1‐oxides into isoxazoles in liquid ammonia

In the reaction of 4‐chloro‐6‐R‐pyrimidine‐1‐oxides (R=CH3 or C6H5) with potassium amide in liquid ammonia at −75°C or with liquid ammonia at −33°C besides the formation of the corresponding 4‐aminopyrimidine‐N‐oxides, a ring contraction into 5‐amino‐3‐R‐isoxazoles (R=CH3 or C6H5) has been observed. A mechanism for the ring contraction reaction is postulated.