具有酰胺键的离子负载双(三氟乙酰氧基)碘苯对乙酰苯胺类化合物的乙酰氧基化反应

以氯乙酰氯、N-乙基对碘苯胺为原料,经酰化反应合成了N-乙基-N-(4-碘苯基)氯乙酰胺,接着与1-甲基咪唑反应,随后在水溶液中和四氟硼酸钠发生阴离子交换,合成了四氟硼酸1-甲基-3-(N-乙基-4-碘苯氨基甲酰甲基)咪唑鎓盐,该四氟硼酸盐在过氧化氢/三氟乙酸酐体系中氧化得到一种新的离子负载的双(三氟乙酰氧基)碘苯试剂四氟硼酸(1-甲基-3-{N-乙基-4-双(三氟乙酰氧基)碘]苯氨基甲酰甲基}咪唑鎓盐)。所合成的碘苯试剂没有吸湿性,在空气中长期放置不变质。以这种新试剂为氧化剂,室温下乙酰苯胺及其衍生物与乙酸区域选择性地发生乙酰氧基化反应,产率较高。该离子负载型碘苯试剂可回收后再生,而再生试剂用于乙酰氧基化反应时活性几乎保持不变。

Direct Acetoxylation of Anilides Using Ion-supported [Bis(trifluoroacetoxy)iodo]benzene with Amide Linkage

Starting from chloroacetic chloride and N-ethyl-p-iodoaniline, N-ethyl-N-(4-iodophenyl) -chloroacetamide was prepared through an acylation reaction, then followed by a nucleophilic substitution with 1-methylimidazole and an anion exchange reaction with sodium tetrafluoroborate in aqueous solution, 3-(N-ethyl-4-Iodophenylcarbamoylmethyl)-1- methylimidazolium tetrafluoroborate was afforded, which was oxidized to give a novel ion-supported bis(trifluoroacetoxy)iodo]benzene {3-N-ethyl-4-bis(trifluoroacetoxy) iodophenylcarbamoylmethyl]-1-methylimidazolium tetrafluoroborate} by using a mixture of hydrogen peroxide and trifluoroacetic anhydride. This new reagent exhibited good stability in air or high humid atmosphere over a few weeks. To explore its application in organic synthesis, various anilides and analogs were acetoxylated by using this reagent and BF3?OEt2 in AcOH at room temperature to give para-acetoxylation products in high yield and good regioselectivity. Moreover, the reagent can be regenerated again from recovered ion-supported iodobenzene easily and retained the same reactivity as before.