Old Selenium Heterocycles Revisited: Synthesis, Spectroscopic, and Structural Characterization of N ‐Acyl‐1,3‐selenazol‐2(3 H )‐imines and 5‐Acyl‐1,3‐selenazol‐2‐amines from Acylselenourea Derivatives

A series of five‐membered selenium heterocycles was prepared from the reaction of various selenoureas and phenacyl bromides. In the case of 1‐acyl‐3‐arylselenoureas N ‐acyl‐1,3‐selenazol‐2(3 H )‐imines are formed, whereas the analogous reaction with 3,3‐disubstituted 1‐acylselenoureas affords 5‐acyl‐1,3‐selenazol‐2‐amines. The compounds were characterized by NMR spectroscopy and mass spectrometry . In addition, the proposed structures were unambiguously confirmed by X‐ray diffraction studies.