Structural assignment of Diels-Alder adducts: an experimental and theoretical approach

A detailed NMR analysis with total assignment of 1H and 13C NMR data for the endo and the exo adducts, obtained by Diels-Alder reaction between 2-cyclohexenone and cyclopentadiene, is described. The unequivocal assignment of the endo and exo structures was performed by 1H and 13C NMR. These assignments were supported by theoretical chemical shift calculations at GIAO/HF level using 6-311+g(2d,p) from optimized structures at the B3LYP/6-31g(d) level.