Synthesis of N-Arylpyrroles, Hetero-Diels−Alder Adducts, and Allylic Amines by Reaction of Unfunctionalized Dienes with Nitroarenes and Carbon Monoxide, Catalyzed by Ru(CO)₃(Ar-BIAN)

The reaction between an unfunctionalized conjugated diene and a nitroarene under CO pressure, catalyzed by Ru3(CO)12/Ar-BIAN (Ar-BIAN = bis(arylimino)acenaphthene), affords the corresponding allylic amine (1), the hetero-Diels−Alder adduct (oxazine) (2), and the N-arylpyrrole (3) in different ratios depending on the experimental conditions. The synthesis of the allylic amine involves an intermolecular catalytic C−H functionalization by a transition metal complex. Compounds 1 and 2 are primary products of the reaction, whereas 3 derives from a following reaction of 2. By running the reaction at 120 °C, the decomposition of 2 to 3 is completely suppressed, allowing for the isolation of 2 in good yields. On the contrary, at 200 °C 2 is completely transformed into 3 during the reaction. The selectivity in allylic amine is somewhat sensitive to the experimental conditions and always ranges between 15 and 25%. Electron-withdrawing substituents on the nitroarene give better results, but electron-donating ones sl...