Photo-Dealkylation of 1,4-Naphthoquinone Derivatives by Irradiation

Here we study a novel dealkylation reaction of 2-alkylamino-3-bromo-1,4-naphthoquinone and its analogs under irradiation. Due to the fact that 1,4-naphthoquinone derivatives play an important role in our biological system, understanding how irradiation affects certain derivatives of 1,4-naphthoquinone is imperative. For instance, 2-isopropylamino-3-bromo-1,4-naphthoquinone is known to dealkylate under irradiation, yielding 2-amino-3-bromo-1,4-naphthoquinone. On the other hand, 2-isopropylamino-1,4-naphthoquinone has no reaction when irradiated. As to examine why this reaction occurs, we are currently focusing on three aspects: the nature of alkylamino substituents at the 2-position, the role of substituents at the 3-position, and the effect of reaction environments. Furthermore, the fate of the dealkylated moiety must be identified to disclose the reaction mechanism. One product was characterized as cyclohexanone during the irradiation of 2-bromo-3-cyclohexylamine-1,4-naphthoquinone. In regards to varying alkyl-amino groups attached at the 2-position, a secondary alkyl group was found to be favored for dealkylation.Similarly, substituents at the 3-position that are viable for dealkylation to occur include: bromine, methoxy, methyl, and chlorine. This suggests that the size of the 3-substituent is pertinent for dealkylation. Lastly, we suspect that oxygen is necessary for this photo-dealkylation to take place. Through examining various factors, we plan to be able to determine the fundamental chemical necessities needed for this unique photo-dealkylation reaction to occur