Stoichiometric and catalytic oxidations with hypervalent organo‐λ3‐iodanes
Stoichiometric and catalytic oxidations with hypervalent organo‐λ3‐iodanes
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DOI：
10.1002/tcr.20104
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发表时间：
2007
期刊：
影响因子：
6.6
通讯作者：
M. Ochiai
中科院分区：
文献类型：
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作者：
M. Ochiai
报道了活化的碘酰苯单体羟基（苯基）碘鎓离子与18-冠-6（18 C6）形成配合物的分离、表征和反应。碘酰苯与HBF（4）在~（18）C_6存在下反应，得到稳定的黄色棱柱状羟基-λ（3）-碘烷配合物PhI（OH）BF（4）·~（18）C_6。X射线结构分析表明，碘（III）和18 C6的三个相邻氧原子之间的紧密接触将负责与未络合的PhI（OH）BF（4）相比，络合物的稳定性增加。还制备了活化的碘酰苯PhI（OH）OTf.18C6.H（2）O与水分子配位碘（III）的水络合物。这些冠醚络合物是高度反应性的，并且用作多用途的化学计量氧化剂，特别是在水中。因此，配合物在温和条件下经历各种官能团如烯烃、炔、烯酮、甲硅烷基烯醇醚、硫化物和酚的氧化转化。后一部分报道了碘苯催化的酮的α-氧化反应，其中原位生成的二酰氧基（苯基）-λ（3）-碘烷作为酮的真实的氧化剂，间氯过苯甲酸（m-CPBA）作为末端氧化剂。在室温下，在催化量的碘苯、BF（3）-Et（2）O和水存在下，在乙酸中用m-CPBA氧化酮，以良好的产率得到α-乙酰氧基酮。注意到水和BF（3）-Et（2）O的使用对于该α-乙酰氧基化的成功是至关重要的。
Isolation, characterization, and reaction of the activated iodosylbenzene monomer, hydroxy(phenyl)iodonium ion, as a complex with 18-crown-6 (18C6) are reported. The reaction of iodosylbenzene with HBF(4) in the presence of 18C6 afforded the hydroxy-lambda(3)-iodane complex PhI(OH)BF(4).18C6 as stable yellow prisms. X-ray structure analysis indicated that the close contacts between the iodine(III) and the three adjacent oxygen atoms of 18C6 will be responsible for the increased stability of the complex compared to the uncomplexed PhI(OH)BF(4). The aqua complex of the activated iodosylbenzene, PhI(OH)OTf.18C6.H(2)O, with a water molecule coordinated to iodine(III) was also prepared. These crown ether complexes are highly reactive and serve as versatile stoichiometric oxidants, especially in water. Thus, the complexes undergo oxidative transformations of a variety of functional groups such as olefins, alkynes, enones, silyl enol ethers, sulfides, and phenols under mild conditions. The latter part reports on the iodobenzene-catalyzed alpha-oxidation of ketones, in which diacyloxy(phenyl)-lambda(3)-iodanes generated in situ act as real oxidants of ketones and m-chloroperbenzoic acid (m-CPBA) serves as a terminal oxidant. The oxidation of a ketone with m-CPBA in acetic acid in the presence of a catalytic amount of iodobenzene, BF(3)-Et(2)O, and water at room temperature affords an alpha-acetoxy ketone in good yield. It is noted that the use of water and BF(3)-Et(2)O is crucial to the success of this alpha-acetoxylation.