Diels–Alder Cycloadditions: A MORE Experiment in the Organic Laboratory Including A Diene Identification Exercise Involving NMR Spectroscopy and Molecular Modeling

The MORE (microwave-induced organic reaction enhancement) technique has been used successfully to prepare two Diels–Alder [π2 + π4] cycloaddition adducts, racemic exo, endo-2,3-dibenzoylbicyclo[2.2.1]hept-5-ene and racemic exo, endo-2,3-dibenzoylbicyclo[2.2.2]octa-5-ene, in high purity and good yields. Microwave synthesis of these two dienes serves as an excellent organic laboratory experiment to demonstrate the rate enhancement advantage of using microwave heating over conventional heating in preparing selected Diels–Alder cycloaddition products. When the splitting patterns of vinyl protons in the NMR spectra of these compounds are used in conjunction with molecular modeling, a pedagogically sound exercise of diene identification emerges from this MORE experiment.