Structure and Reactivity of Organoaluminum Derivatives of Amino Acids

The reaction of AlR 3 with 1 molar equiv of anthranilic acid yields the dimeric carboxylates [R 2 Al(O 2 CC 6 H 4 -2-NH 2 )] 2 [(R = Me ( 3a ) or Et ( 3b )] in high yields. The addition of 2 molar equiv of AlR 3 to anthranilic acid results in the formation of the tetranuclear complexes [R 2 Al] 4 [μ-O 2 CC 6 H 4 -2-μ-NH] 2 [(R = Me ( 4a ) or Et ( 4b )], where both protic functionalities are involved in the alkane elimination. The addition of γ-picoline to a solution of 4b in toluene results in a disruption of the tetranuclear cluster and affords Et 2 Al(η-O 2 CC 6 H 4 -2-NH)AlEt 2 (py-4-Me) ( 5 ). The reaction of 2 molar equiv of AlMe 3 with glycine yields the alkylaluminum carboxylate Me 2 Al(O 2 CCH 2 NH 2 )AlMe 3 ( 6 ), in which only the carboxylic group is deprotonated. When more equivalents of AlMe 3 are employed, the alkylation of the carboxylate group of glycine occurs and the aluminum alkoxide Me 2 Al[OC(CH 3 ) 2 CH 2 NH 2 ]AlMe 3 ( 7 ) was isolated as one of the products of the complex postreaction mixture. The resulting compounds have been characterized by NMR and IR spectroscopy, and the molecular structure of compounds 4b and 7 has been confirmed by X-ray crystallography. On the basis of the reported studies, the general pathway for an interaction of amino acids with aluminum alkyls is proposed and some new insight into the reaction mechanism of the carboxylate group alkylation is provided.