Reactions of amides with organoaluminium: a useful synthetic route to aluminium diketiminates

Abstract

The reaction of N-tert-butylbenzamide (^tBuNHCOPh) with 1.1 molar equivalents of Me₃Al in refluxing hexane afforded a five-coordinated dimeric compound [Me₂Al{η²-^tBuNC(Ph)(μ-O)}]₂1, whereas 2.2 molar equivalents yielded a monomeric compound [Me₂Al{η²-^tBuNCPh(μ-O)}AlMe₃] 2. Reaction of PhCONHAr with 1 molar equivalent of Me₃Al in toluene at 25 °C, gave four-coordinated dimeric eight-membered ring compounds [Me₂Al{μ-η²-(p-XC₆H₄)NC(Ph)O}]₂ (X = OMe 3 or 4). Benzanilide (PhNHCOPh) with 1.2 molar equivalents of Me₃Al in refluxing toluene resulted in aluminium amidate 4 and a trace amount of an aluminium diketiminate, [Me₂Al{η²-PhNC(Ph)C(H)C(Ph)NPh}] 5. Furthermore, PhCONHC₆H₄X-p reacts with 2 molar equivalents of R₃Al in refluxing toluene affording aluminium diketiminate compounds, [R₂Al{η²-(p-XC₆H₄)NC(Ph)C(R′)C(Ph)N(p-XC₆H₄)}] (R = Et, R′ = Me, X = H 6; R = Et, R′ = Me, X = Cl 7; R = Me, R′ = H, X = Cl 8; R = Me, R′ = H, X = Me 9; R = Et, R′ = Me, X = Me 10). Thus, this process offers a readily available synthetic route to the preparation of aluminium diketiminates which is otherwise difficult with aromatic substituents.