Reaction of 1,4-napthoquinones with diamines
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We studied the reactivity of 1,4-naphthoquinone derivatives with diamines. For example, in 2-bromo-3-methoxy-1,4-naphthopquinone there are two potentially reactive groups that would react with a nucleophile such as an amine.Interestingly, depending upon the reaction condition, the mode of reaction is different, yielding a few different products. The reactivity of an amino group in 1,2-ethanediamine is affected by the substituent. Thus, in the reaction with 2-bromo-3-methoxy-1,4-naphthoquinone in methanol, N-acetyl-1,2-diaminoethane reacted as a monofunctional amine and formed 2-(2-N-acetylaminoethylamino)-3-bromo-1,4-naphthoquinone. On the other hand, 1,2-diaminoethane, in the reaction with 2-bromo-3-methoxy-1,4-naphthoquinone, yielded a tricyclic 1,4-diazaphenanthrene derivative; most effectively when reacted in a freezer. The salt form, 1,2-diaminoethane dihydrochloride, in the presence of an equimolar amount of base, was found to form a Schiff base in the reaction with in methanol. The best yields were obtained when the reaction was carried out in a microwave reactor. The reactions of other 1,4-naphthoquinone derivatives such as 2-bromo-1,4-naphthoquinone, 2-chloro-1,4-naphthoquinone, 2,3-dibromo-1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone and 2,3-dimethoxy-1,4-naphthoquninone as well as the reaction mechanisms are presented here.