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

The reaction of N-tert-butylbenzamide ((BuNHCOPh)-Bu-t) with 1.1 molar equivalents of Me3Al in refluxing hexane afforded a five-coordinated dimeric compound [Me2Al{eta (2)-(BuNC)-Bu-t(Ph)(mu -O)}](2) 1, whereas 2.2 molar equivalents yielded a monomeric compound [Me2Al{eta (2)-(BuNCPh)-Bu-t(mu -O)}AlMe3] 2. Reaction of PhCONHAr with 1 molar equivalent of Me3Al in toluene at 25 degreesC, gave four-coordinated dimeric eight-membered ring compounds [Me2Al{mu-eta (2)-(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{eta (2)-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{eta (2)-(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.