Syntheses of Hypervalent Allenyliodinanes and Iodo-Claisen Rearrangement

最近，我们报道了在BF3-Et2O存在下，丙基硅烷与芳烷在温和条件下发生还原性碘离子- clisen重排，产率高的邻丙基碘芳烃。还原性邻丙基化反应可能涉及丙烯基（芳基）碘烷的中间形成，并经历[3,3]-异位重排。交叉产物的缺乏证明了重排是分子内的。对于（对甲氧基）芳基二烷，观察到一种异碘-克莱森重排。为了检测烯基（芳基）碘烷对芳烷还原丙基化反应的干预作用，我们进行了1-羟基-1,2-苄基碘醇-3(1H)- 1与1,3-二-（三甲基硅基）-3-甲基丁-1-炔的反应。然而，这个反应出人意料地生成了烷基过氧碘。烷基过氧碘烷从来没有被合成过，可能是因为它们容易分解。用叔丁基过氧化氢在BF_3-Et_2O的存在下，在氯仿中室温处理1-羟基-1,2-苯并碘醇-3(1H)- 1，可得1-叔丁基-过氧基-1,2-苯并碘醇-3(1H)- 1为无色平板，收率为85%。通过光谱数据对过氧碘烷进行了充分的表征，并通过单晶x射线分析明确了其结构。我们发现过氧碘烷在有机合成中是一种多功能的氧化试剂，它可以将硫化物氧化为亚砜或砜，将硒化物氧化为硒氧化物，将膦氧化为氧化膦，将烯烃氧化为环氧化物。还实现了二硫缩醛对酮的脱保护以及在苯基位置氧化生成羰基化合物。此外，还发现过氧碘烷是一种将胺氧化为亚胺的有效试剂。

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.