可见光诱导8-氨基喹啉衍生物二氟烷基化反应

Visible Light Induced Difluoroalkylation of 8-Aminoquinoline Derivatives

摘要:

室温条件下，研究了铜催化可见光诱导8-氨基喹啉衍生物C5位二氟烷基化反应。以蓝色LED为光源，面式-三(2-苯基吡啶)合铱配合物〔fac-Ir(ppy)3〕为光敏剂，8-氨基喹啉衍生物与二氟溴乙酸乙酯产生的二氟乙酸乙酯自由基发生C—C偶联反应。在CuI催化下合成15个C5位二氟烷基化的8-氨基喹啉衍生物（Ⅲa~Ⅲo）。通过1HNMR、13CNMR、FTIR和HR-MS对产物的结构进行确证。8-氨基喹啉衍生物的转化率为50%~90%，反应收率范围为21%~58%。该反应条件温和，含有卤素、硫醚和氰基官能团的底物都能发生反应。自由基捕获剂2,2,6,6-四甲基哌啶-1-氧（TEMPO）能捕获到二氟乙酸乙酯自由基，验证该反应过程可能经过自由基单电子转移。

Abstract:

A copper-catalyzed visible light induced difluoroalkylation reaction of 8-aminoquinoline derivatives at the C5- position was developed at room temperature. The C—C coupling reaction between 8-aminoquinoline derivatives and free radicals of ethyl difluoroacetate produced by ethyl difluorobromoacetate was carried out with blue LED as light source, fac-Tris[2-(2-pyridinyl)phenyl] iridium(Ⅲ) complexes (fac-Ir(ppy)3) as photosensitizer. Fifteen difluoroalkylated 8-aminoquinoline derivatives (Ⅲa~Ⅲo) at the C5 position were synthesized in the presence of a catalytic amount of cuprous iodide. These products were characterized by 1HNMR, 13HNMR, FTIR, and HR-MS. The conversion rates of starting materials were50%~90%, and yields of products was in the range from 21% to 58%. The reaction conditions are mild, and the substrates containing halogen, thioether, and cyan functional groups can react. Free radical scavenger2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) could capture free radicals of ethyl difluoroacetate, indicating that the reaction process may undergo free radical single electron transfer.