Introduction of abnormal N-heterocyclic carbene as an efficient organocatalyst: ring opening polymerization of cyclic esters.

The recently isolated abnormal N-heterocyclic carbene (aNHC) has been established as an efficient organocatalyst in ring opening polymerization of three different cyclic esters rac-lactide (rac-LA), ε-caprolactone (ε-CL), and δ-valerolactone (δ-VL). Preliminary DFT calculations indicate that aNHC can be a better organocatalyst than the corresponding nNHC counterpart. This journal is © The Royal Society of Chemistry 2011