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

The 2-aminophenylaluminum dihydride (2-TMP-C6 H4 )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 Ph2 CCNR (R=iPr or 2,6-iPr2 C6 H3 , 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.