Abstract
2-Chloronaphtho[2, 3-b]furan-4, 9-dione (4) was allowed to react with sodium phenoxide to produce 2-phenoxynaphtho[2, 3-b]furan-4, 9-dione (8) in 55% yield. Also, in a similar manner, 8 was obtained from the reactions of 2-bromonaphtho[2, 3-b]furan-4, 9-dione (5), 2-iodonaphtho[2, 3-b]furan-4, 9-dione (6) and 2-nitronaphtho[2, 3-b]furan-4, 9-dione (7) with sodium phenoxide. The reaction of 4 with sodium methoxide gave methyl 3-hydroxy-1, 4-naphthoquinone-2-acetate (9) in which the furan ring was cleaved. 2-Phenylthionaphtho[2, 3-b]furan-4, 9-dione (11) and 2-methylthionaphtho[2, 3-b]furan-4, 9-dione (12) were obtained from the reactions of 4 with thiolates in 63% and 62% yields, respectively. Furthermore, 4 was treated with sodiomalonic ester ot give diethyl 2-(naphtho[2, 3-b]furan-4, 9-dione-2-yl)malonate (13) in 28% yield. Compound 13 was also obtained from the reactions of 5 and 7 with sodiomalonic ester. All these nucleophilic substitutions were carried out at room temperature. It was found that 4-7 had a high reactivity with various nucleophilic reagents.
