The Synthesis of N-Benzyl-2-azanorbornene via Aqueous Hetero Diels–Alder Reaction. An Undergraduate Project in Organic Synthesis and Structural Analysis

Abstract

The synthesis of N-benzyl-2-azanorbornene via aqueous hetero Diels�Alder reaction of cyclopentadiene and benzyliminium chloride formed in situ from benzylamine hydrochloride and formaldehyde is described. Characterization of the product was achieved by IR and NMR spectroscopies. The spectral data acquired are thoroughly discussed. Numerous coupling constants were extracted from the 1H NMR spectrum. They provide a valuable material to familiarize students with the different types of proton�proton coupling patterns and their typical ranges. Karplus type correlations served to calculate 3J vicinal coupling constants as a function of dihedral angles. These computational studies involved molecular modeling. Because the synthetic part is rather straightforward and easy to carry out, this experiment is suitable for an introductory laboratory course where it can serve to illustrate the concepts of green chemistry and atom efficiency. Emphasis can also be placed on structural analysis for use within a spectroscopy course even if there is no activity component associated with it. Last but not least, the whole project provides ample materials for an advanced undergraduate laboratory in green chemistry that combines organic synthesis, structural analysis, and theoretical calculations.