C–C Bond Formation at an Aluminacyclopropane

The reactivity of the aluminacyclopropane compound K[Al(NON)(η 2 -C 2 H 4 )] (NON = κ N, N ’-[O(SiMe 2 NDipp) 2 ] 2–; Dipp = 2,6- i Pr 2 C 6 H 3 ) toward isocyanides R–NC (R = Cy, Ad, t Bu; Cy = cyclohexyl, Ad = 1-adamantyl) and benzophenone is described. All reactions proceed via insertion of the substrate into an Al–C bond of the aluminacycle, with C–C bond formation leading to ring-expanded products. With isocyanide substrates, either monoinsertion (R = Cy, Ad, t Bu) to afford the four-membered aluminacyclobuta-1-imine ring, or double insertion (R = t Bu) to form an aluminacyclopenta-1,2-diimine ring is observed. The reaction with benzophenone affords the corresponding insertion product that incorporates the C═O functionality to form an expanded five-membered AlOC 3 ’alumina-tetrahydrofuran’ ring. The NON-ligand of this product undergoes a thermally induced, intramolecular 1,3-silyl retro-Brook rearrangement to afford the corresponding “Al(NNO)” product ([NNO] 2– = κ N, O -[N(Dipp)SiMe 2 N(Dipp)SiMe 2 O] 2– ).