Abstract
One of the important methods of generating oxazoles is the Robinson-Gabriel reaction. Quantum chemical density functional methods have been used in this work to investigate the mechanism of the reaction. The barrier for the cyclization step of the reaction has been estimated to be 31.4 kcal/mol for oxazole in the absence of any catalyst. The transition state involves participation of explicit water molecule. The same reaction under hemi-aminal condition requires marginally less barrier 28.2 kcal/mol. In the acidic medium (with water participation), the barrier is significantly reduced to 9.5 kcal/mol when the protonation happens at the amide center. Protonation at keto carbon is less favorable but such a condition helps the cyclisation in a barrier less process. Additionally, it was also found that the water molecules play an essential role during the reaction, even in the acidic condition.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have