Understanding the substitution with nucleophiles on a variety of 1,4- naphthoquinones is paramount in synthesizing biologically active quinone derivatives. Due to the two reactive functional groups in aminoalkylthiols with 1,4-naphthoquinones that have two potential reactive sites, the 2- and/or 3-positions, it would provide with an ideal system to study the mechanistic details involved in the substitution reactions of 1,4-naphthoquinones. For example, in the reaction of 2-bromo-3-methoxy-1,4-naphthoquinone with 2-aminoethanethiol, we isolated a cyclic product, 1-aza-4-thia-2,3-dihydroanthracene-9,10-dione exclusively. On the other hand, the reaction of 2-methoxy-1,4-naphthoquinone in the reaction of 2-aminoethanethiol affords only monosubstituted product, 2-(2-mercaptoethylamino)-1,4-naphthoquinone. Interestingly, in the reaction of 2-N-butylaminoethanethiol, 2-bromo-3-methoxy-1,4-naphthoquinone and 2-methoxy-1,4-naphthoquione both form the same cyclic product, N-butyl-2-aza-4-thia-2,3-dihydroanthracene-9,10-dione. The effect of the alkylsubstitution at N-atom in 2-aminothanethiol is in progress.