Chapter Four - Heterocycles from Donor–Acceptor Interactions

Abstract

Abstract The quinone ring is found commonly in nature. Quinones, including heterocyclic analogs, are involved in numerous biochemical processes because of their facile reduction–oxidation. They play an important role in electron therapeutic value as antitumor, antibacterial, antifungal, and anticancer agents. Additionally and in general, 1,1,2,2-tetracyanoethene (TCNE) as well as its derivatives containing the dicyanomethylene moieties are known as electron-deficient substances. This chapter is concerned with selected reactions of 1,1,2,2-tetracyanoethene (TCNE, 1 ), 2,3-dichloro-1,4-naphthoquinone ( 2a ) and 2,3-dicyano-1,4-naphthoquinone ( 2b ), 2-(1,3-dioxo-2,3-dihydro-1( H )-indene-2-ylidene)propanedinitrile ( 3 ), 3,4,5,6-tetrachloro-1,2-benzoquinone ( 4 ), 2,3,5,6-tetrachloro-1,4-benzoquinone ( 5 ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone ( 6 ) as π-deficient compounds, have been used or potentially used in heterocyclic synthesis. The chemistry here is dominated by addition and addition–elimination reactions accompanied by donor–acceptor interactions that would undergo charge-transfer complex formation. Reactions of nucleophilic donors with acceptors 1–6 were investigated. Moreover, cycloadditions like [2 + 2], [4 + 2], and others with selective π-acceptors serve as effective tools in the synthesis of heterocyclic compounds.