Syntheses of Hypervalent Allenyliodinanes and Iodo-Claisen Rearrangement

最近，我们报道了在BF3-Et2O存在下，炔丙基硅烷与芳基碘烷在温和的条件下发生还原的碘-克莱森重排反应，以较高的产率生成邻炔丙基碘芳烃。还原邻丙烯酰化反应可能涉及烯基(芳基)碘烷的中间体形成，该中间体发生[3，3]-Sigmatroic重排。交叉产物的缺乏证明了重排的分子内性质。与(对甲氧基)芳基碘烷发生异构化碘-克莱森重排反应。为了检测烯基(芳基)碘在芳基碘烷还原烷基化反应中的干预作用，我们进行了1-羟基-1，2-苯并碘-3(1H)-酮与1，3-二-(三甲基硅基)-3-甲基-1-炔的反应。然而，该反应导致了意想不到的(烷基过氧基)碘烷的形成。烷基过氧基碘烷从未被合成过，可能是因为它们很容易分解。当1-羟基-1，2-苯并碘-3(1H)-酮在BF_3-Et_2O存在下室温氯仿中与叔丁基氢过氧化氢反应时，得到无色的烷基过氧碘-1-叔丁基-1，2-苯并-碘-3(1H)-酮，产率为85%。过氧碘烷的结构经单晶X-射线分析明确确定，并用光谱数据进行了充分表征。我们发现，在有机合成中，过碘烷是一种用途广泛的氧化剂，可以将硫化物氧化成亚硫醚或砜，将硒化合物氧化成硒氧化物，将膦氢氧化成膦氧化物，将烯烃氧化成环氧化物。还实现了二硫代缩醛对酮的去保护以及在生成羰基化合物的苄基位置上的氧化。此外，过氧碘烷被发现是一种有效的胺氧化为亚胺的试剂。

Recently, we reported that the reaction of propargylsilanes with aryliodinanes in the presence of BF3-Et2O undergoes a reductive iodonio-Claisen rearrangement under mild conditions, yielding ortho-propargyl iodoarenes in good yields. The reductive ortho-propargylation probably involves the intermediate formation of allenyl(aryl)iodinanes, which undergo [3,3]-sigmatropic rearrangement. The lack of the crossover products argues for the intramolecularity of the rearrangement. With (p-methoxy)aryliodinanes, an ipso iodonio-Claisen rearrangement is observed. To detect the intervention of the allenyl(aryl)iodinanes in the reductive propargylations of aryliodinanes, we have carried out the reaction of 1-hydroxy-1,2-benziodoxol-3(1H)-one with 1,3-bis-(trimethylsilyl)-3-methylbut-1-yne. The reaction, however, led to the unexpected formation of an (alkylperoxy)iodinane.Alkylperoxyiodinanes have never been synthesized probably because of their high tendency to decompose. When 1-hydroxy-1,2-benziodoxol-3(1H)-one was treated with tert-butyl hydroperoxide in the presence of BF_3-Et_2O in chloroform at room temperature, the alkylperoxyiodinane, 1-tert-butylperoxy-1,2-benziodoxol-3(1H)-one was obtained as colorless plates in 85% yield. The peroxyiodinane was fully characterized by spectral data and the structure was unambiguously established by a single-crystal X-ray analysis. We found that the peroxyiodinane is a versatile oxidizing reagent in organic synthesis, and can oxidize sulfides to sulfoxides or sulfones, selenides to selenoxides, phosphines to phosphine oxides, and olefins to epoxides. Deprotection of dithioacetals to ketones as well as oxidation at benzylic positions yielding carbonyl compounds were also achieved. Furthermore, the peroxyiodinane was found to be an efficient reagent for oxidation of amines to imines.