SYNTHESIS OF N-CARBOXYETHYLNAPHTHALIMIDES WITH FRAGMENTS OF PRIMARY AND SECONDARY AMINES IN POSITIONS 4 AND 5

Abstract

New N-carboxyethyl-1,8-naphthalimides with fragments of morpholine and piperidine in positions 4 and 5 of naphthalene ring were synthesized by acylation of β-alanine with 4,5-dimorpholino- and 4,5-dipiperidino-1,8-naphthalic anhydrides in acetic acid. Corresponding 4,5-disubstituted naphthalic anhydrides were obtained by nucleophilic substitution of chlorine atoms in 4,5-dichloro-1,8-naphthalic anhydride on corresponding electron donating amino substitutients using dimethyl sulfoxide as solvent. Starting 4,5-dichloro-1,8-naphthalic anhydride was obtained by oxidation of 4,5-disubstituted acenaphthene with sodium dichromate in acetic acid. The same sequence of reactions can not be used for synthesis of N-carboxyethyl-1,8-naphthalimides with 2-hydroxyethylamino groups in positions 4 and 5 as the main product of reaction of 4,5-dichloro-1,8-naphthalic anhydride with ethanolamine is the product of nucleophilic addition of primary amine to carbonyl group of anhydride cycle but not the product of chlorine atoms substitution. Thus N-carboxyethyl-4,5-di(2-hydroxyethylamino)-1,8-naphthalimide was obtained by acylation of β-alanine with 4,5-dichloro-1,8-naphthalic anhydride followed by chlorine atoms substitution in N-carboxyethyl-4,5-dichloro-1,8- naphthalimide. The synthesized N-carboxyethylnaphthalimides with morpholino-, piperidino and 2-hydroxyethylamino groups in positions 4 and 5 are orange crystal substances with yellow fluorescence. Their structure was confirmed by IR and NMR 1H spectroscopy. The obtained fluorophores have weak fluorescence in aqueous solutions but their fluorescence increases 14-22 times by addition of albumin, so they can be considered as perspective substances for their further research as fluorescent probes for proteins.