A C(sp²)−H Dehydrogenation of Heteroarenes and Arenes by a Functionalized Aluminum Hydride

The 2-aminophenylaluminum dihydride (2-TMP-C₆H₄)AlH₂ (2) has been prepared and characterized for the first time. Compound 2 features an intramolecular N⋅⋅⋅Al donor–acceptor bond. 2 reacted with N-methylpyrrole and N-methylindole (both at 50 °C) by means of the elusive AlH C(sp²)−H dehydroalumination to aluminum heteroaryls (3 and 4). Moreover, 2 reacted with PhCCSiMe₃ (at room temperature) and Ph₂CCNR (R=iPr or 2,6-iPr₂C₆H₃, at −30 to 20 °C) to yield aluminaindene heterocycle (8) and alumina-aza-naphthalene heterocycle (9 and 10), respectively. These reactions underwent hydroalumination followed by AlH C(sp²)−H dehydroalumination. The reaction mechanism has been studied by combining experiment and quantum chemical calculations, with the result that the key heteroarene or arene C(sp²)−H bond activation is involved under cooperative interaction by the inherent N/Al donor/acceptor pair. The reported reactions open a straightforward route to heteroaryl and unique heterocyclic aluminum compounds.