Diels-Alder reactions of five-membered heterocycles containing one heteroatom.

Abstract Diels–Alder reactions of five-membered heterocycles containing one heteroatom with an N -arylmaleimide were studied. Cycloaddition of 2,5-dimethylfuran ( 4 ) with 2-(4-methylphenyl)maleimide ( 3 ) in toluene at 60 °C gave bicyclic adduct 5 . Cycloadditions of 3 with 2,5-dimethylthiophene ( 11 ) and 1,2,5-trimethylpyrrole ( 14 ) were also studied. Interestingly, the bicyclic compound 5 cleanly rearranged, with loss of water, when treated with p -toluenesulfonic acid in toluene at 80 °C to give 4,7-dimethyl-2- p -tolylisoindoline-1,3-dione ( 6 ).