LiO t Bu Promoted 5‐ Exo– dig Cyclization of Propargyl Alcohols and Isocyanates for the Synthesis of Multisubstituted 3 H ‐Oxazol‐2‐ones and Oxazolidin‐2‐ones

This study presents an efficient procedure for synthesis of 3,4,5‐trisubstituted 3 H ‐oxazol‐2‐ones and 3,4‐disubstituted (Z)‐oxazolidin‐2‐ones from substituted propargyl alcohols and aryl/alkyl isocyanates in the presence of LiO t Bu, a base, and DMF, a solvent. This one‐step, low‐cost and gram scale synthesis exhibits superior atom economy, good to excellent yields, enhanced substrate scope and, high functional group tolerance and uses column chromatography‐free purifications. Further, a product containing bromo substituent was successfully examined for Suzuki coupling with a view to amplifying the complexity of the molecule. Finally, the three component (aniline, Di‐tert‐butyldicarbonate and propargyl alcohol) reaction was demonstrated to get the oxazolon‐2‐ones (3 H ‐oxazol‐2‐one and oxazolidin‐2‐one).