Versatile hypervalent-iodine(III)-catalyzed oxidations with m-chloroperbenzoic acid as a cooxidant
Versatile hypervalent-iodine(III)-catalyzed oxidations with m-chloroperbenzoic acid as a cooxidant
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DOI：
10.1002/anie.200501688
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发表时间：
2005-01-01
影响因子：
16.6
通讯作者：
Kita, Y
中科院分区：
文献类型：
--
作者：
Dohi, T;Maruyama, A;Kita, Y
6193 Angew。化学。Int。2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim dizer，如铅，汞和铊试剂（图1）它们通常用作化学计量氧化剂，但也可能在催化条件下进行氧化。事实上，据报道，以催化量的二氟化碘苯或4-二氟化碘甲苯进行氧化氟化反应，其中碘芳烃的碘基团的再氧化是通过电子方式进行的。[2,3]然而，据我们所知，形成其他键类型的催化体系尚未被报道。这可能是由于在反应体系中缺乏将有机碘(i)再氧化为高价碘（iii）的有效程序[4-8]。虽然已经报道了用高碘酸钠（NaIO4）、[6]三氧化铬（CrO3）、[7]和二甲基二氧环[8]制备[6]的新方法，但在产品收率、操作方便性等方面仍不尽如人意。我们最近开发了环境友好，可回收的高价碘（iii）试剂1a-c，具有高反应活性在其合成过程中，我们意识到需要制备出接近定量产率的1a，使其成为一种实用的可回收试剂；我们还发现，只有在稀乙酸/二氯甲烷中使用甲基氯过苯甲酸（mCPBA）[10]的氧化体系才适合此目的。这个有趣的方面促使我们探索这些金刚烷基可回收试剂与mCPBA结合作为化学计量化学氧化剂作为催化剂的可能性。在这里，我们展示了催化量的高价碘（iii）试剂的氧化转化，这使得多种CÀ O甚至CÀC键形成成为可能。依托之前合成1a的条件，我们首先考察了苯酚5a[11]与0.1当量的二乙酸苯碘啶（PIDA）的氧化螺环化反应，结果令人失望（表1，条目1）。因此，对反应条件进行了优化。用3a代替PIDA，观察到催化反应（条目2）。随着三氟乙酸（CF3CO2H）用量的增加，催化效率增加（条目2和3）。在没有3a的情况下，没有观察到反应。有趣的是，在这些病例中观察到5a的快速转化。酸的性质和水的存在也有影响（条目4 - 7）。高价碘（iii）试剂3d的检测结果最好（条目10和11）。可以将3d的量降低到0.01当量，而不会显著降低催化效率（条目11）。用3d与过氧乙酸、过硼酸钠、过硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠、硼酸钠均不能成功地对5a进行旋环化。
6193 Angew. Chem. Int. Ed. 2005, 44, 6193–6196 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim dizers such as lead, mercury, and thallium reagents (Figure 1).[1] They are generally used as stoichiometric oxidants, though it may be possible to carry out oxidations under catalytic conditions. Indeed, oxidative fluorination reactions with a catalytic amount of iodobenzene difluoride or 4-iodotoluene difluoride were reported in which the reoxidation of the iodine groups of iodoarenes was carried out electronically.[2, 3] However, to our knowledge, a catalytic system for the formation of other bond types has not yet been reported. This is probably due to the lack of efficient procedures for the reoxidation of organoiodine (i) to hypervalent iodine (iii) species [4–8] in the reaction system. Although new preparative methods that use sodium periodate (NaIO4),[6] chromium trioxide (CrO3),[7] and dimethyldioxirane [8] have been reported, they remain unsatisfactory in terms of product yield, ease of operation, and other aspects. We have recently developed environmentally friendly, recyclable hypervalent iodine (iii) reagents 1a–c with high reactivities.[9] In its synthesis, we realized the need to prepare 1a with nearly quantitative yield to make it a practical recyclable reagent; we also found that only an oxidation system using metachloroperbenzoic acid (mCPBA)[10] in dilute acetic acid/dichloromethane was suitable for this purpose. This interesting aspect prompted us to explore the possibility of these adamantane-based recyclable reagents as catalysts by combination with mCPBA as a stoichiometric chemical oxidant. Herein, we demonstrate oxidative transformations with catalytic amounts of hypervalent iodine (iii) reagents, which enable versatile CÀ O and even CÀC bond formations. Relying on the previous conditions to synthesize 1a, we first examined the oxidative spirocyclization reaction of the phenol 5a [11] with 0.1 equivalent of phenyliodine diacetate (PIDA), which gave disappointing results (Table 1, entry 1). Therefore, the reaction conditions were optimized. With 3a instead of PIDA, a catalytic reaction was observed (entry 2). As the amount of trifluoroacetic acid (CF3CO2H) increased, the catalytic efficiency increased (entries2 and 3). In the absence of 3a, no reaction was observed. Interestingly, the rapid conversion of 5a was observed in these cases. The nature of the acids and the presence of water were also influential (entries4–7). The hypervalent iodine (iii) reagent 3d gave the best results of those examined (entries10 and 11). It was possible to decrease the amount of 3d to as low as 0.01 equivalent without a significant loss in catalytic efficiency (entry 11). The spirocyclization of 5a using 3d with other cooxidants such as peracetic acid,[4] sodium perborate,[5] NaIO4,[6] and CrO3[7] were not successful.