NHC Organocatalysis in D2O for the Highly Diastereoselective Synthesis of Deuterated Spiropyran Analogues

Metal-free N-heterocyclic carbene (NHC) organocatalysis in D2O medium was elegantly utilised for the synthesis of highly diastereoselective deuterated spiropyran derivatives. Selective deuteration was exclusively achieved on the C5 carbon atom of the pyran ring. Quantum chemical calculations were performed to prove the preferential formation of a single diastereomer from the possible four diastereomers. The scope of NHC organocatalysis in D2O was also extended for the synthesis of deuterated spirooxindole derivative.