Nucleophilic substitutions of 2‐chloronaphtho[2,3‐ b ]furan‐4,9‐dione with amines

2‐Chloronaphtho[2,3‐ b ]furan‐4,9‐dione 4 was allowed to react with pyrrolidine to produce 2‐(1‐pyrrolidinyl)naphtho[2,3‐ b ]furan‐4,9‐dione 8 in 64% yield. In a similar manner, the reaction of 4 with cyclic amines (piperidine, morpholine, 4‐substituted piperazines, etc .) gave the desired compounds. 2‐Dimethylaminonaphtho[2,3‐ b ]furan‐4,9‐dione 20 and 2‐propylaminonaphtho[2,3‐ b ]furan‐4,9‐dione 23 were obtained from the reactions of 4 with amines in 67% and 48% yields, respectively. Furthermore, the reactions of 4 with acyclic amines (diethylamine, dipropylamine, isopropylamine, butylamine, etc .) gave the desired compound. Compound 4 was treated with sodium azide to give 2‐azidonaphtho[2,3‐ b ]furan‐4,9‐dione 28 in 42% yield. All these nucleophilic substitutions were carried out at room temperature. It was found that 4 showed high reactivity for amines. Unexpectedly, 2‐morpholinonaphtho[2,3‐ b ]furan‐4,9‐dione 13 was obtained from the reaction of 4 with 1‐morpholino‐1‐cyclohexene.