Green Synthesis and Unexpected Transformation of New Oxothiazolo[3,2‐<i>c</i>]Pyrimidine Carbonitriles

ABSTRACT A swift microwave‐assisted Mannich cyclization between enaminocarbonitriles, formaldehyde, and primary amines giving 3‐oxothiazolo[3,2‐ c ]pyrimidine carbonitriles in excellent yields is reported. This protocol has some advantages such as atom‐economy, highly practical, water‐assisted, catalyst‐ and chromatography‐free. Interestingly, some unexpected aryl thiazolidinones were also accessed over a retro‐Mannich‐cyclization sequence in the reaction of thiazolo[3,2‐ c ]pyrimidine carbonitriles with mercapto acetic acid.