Isohexide Dinitriles: a versatile family of renewable platform chemicals

Abstract

New 2/5 1-carbon extended isohexide building blocks are now synthetically accessible by a convenient, selective base-catalyzed epimerization of the corresponding dinitriles. Kinetic experiments using the strong organic base 1,8-diazabicyclo[5.4.0]undec-7- ene (DBU) show that all three possible isohexide dinitrile isomers are in a dynamic equilibrium. An epimerization mechanism is proposed, based on DFT calculations. Structural identification of all three possible isomers is based on NMR analysis as well as single crystal x-ray crystallography. DFT calculations confirmed that the observed crystal structures are indeed the lowest energy conformers of these isohexide derivatives.