Studies on the use of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline for the synthesis of acylamino acid anilides and p-nitroanilides

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Abstract
The use of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) for coupling acyl-L-amino acids with aniline and p-nitroaniline was investigated. Optically pure anilides are obtained in good yield, but partial racemization occurred in 1 case. p-Nitroanilides cannot be obtained under similar conditions, but if the reaction solvent is removed and the residue left for several days, coupling occurs giving a racemic product in moderate yields. Reaction mechanisms are proposed based on isolated and characterized intermediates. N-benzoylamino acid anilides and p-nitroanilides are cleaved within a few minutes by hydrogen bromide in acetic acid to give the N-benzoylamino acid and the amine.