Reactions and interactions between peri-groups in 1-dimethylamino-naphthalene salts: An example of a "through space" amide

Abstract

8-Dimethylaminonaphthalene-1-carbaldehyde reacts readily at 0°C with benzoyl or pivaloyl chloride by O-acylation and formation of a N-C bond (1.566(2)-1.568(3) Å) between the peri-substituents to give a salt. The reaction is promoted by electron donation from the dimethylamino group to the carbonyl group, akin to the properties of an amide. In contrast, the corresponding methyl ester and N,N-diisopropylamide react with acid in ether by protonation of the dimethylamino group and formation of a hydrogen bond to the carbonyl group, while under similar conditions the N,N-dimethylamide undergoes ready hydrolysis to the acid. The structures of products are determined by X-ray crystallography, and from the latter hydrolysis crystals containing zwitterionic 1-dimethylammonium-naphthalene-8-carboxylate and the corresponding O-protonated cation along with dimethylammonium and triflate ions were obtained.