Deoxygenative functionalization of hydroxy groups via xanthates with tetraphenyldisilane
Deoxygenative functionalization of hydroxy groups via xanthates with tetraphenyldisilane
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DOI：
10.1021/jo991715r
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发表时间：
2000-05-05
影响因子：
3.6
通讯作者：
Yokoyama, M
中科院分区：
文献类型：
--
作者：
Togo, H;Matsubayaski, S;Yokoyama, M
碳水化合物、核苷和抗生素中羟基的脱氧反应是非常重要的，因为它们的功能转化。今天，最有效和最实用的羟基脱氧方法是Barton-McCombie反应，它是黄药与三丁基锡氢化物/AIBN或三丁基锡氢化物/Et3B体系1或最近在过氧化氢或Et3B，2三烷基硅烷在过氧化氢/硫醇(极性反转催化剂)存在下，3，5，10-二氢硅菲/AIBN，4三(三甲基硅基)硅烷/AIBN，5二丁基氧膦/AIBN或Et3B，6或膦-硼烷/AIBN的反应。7 Barton-McCombie反应和具有替代试剂的改进的Barton-McCombie反应在有机合成中得到了广泛的应用。然而，众所周知，三丁基锡氢化物的使用存在几个问题，如毒性和处置、加工以及从产品中完全去除锡物种。苯基硅烷、二苯基硅烷和二丁基氧化膦没有那么活跃，尽管这些化合物的毒性比锡化合物小得多。此外，这些体系仅限于脱氧反应。据我们所知，糖黄药与三丁基锡氢化物分子间加成反应的报道较少，且产率适中。8最近，我们报道了空气稳定的四芳基二硅烷用于三种类型的与烷基溴化物的自由基反应，如还原、烯烃还原加成和杂芳基的烷基化。9在这里，作为开发四芳基二硅烷作为环境友好体系用于有机合成的计划的一部分，我们想要报告一种新的从醇通过黄药脱氧形成烷基的方法，以及它们与四苯基二硅烷在乙酸乙酯中的AIBN存在下还原为相应的碳氢化合物、与活性烯烃的还原加成以及杂芳碱的烷基化反应。首先，研究了在乙酸乙酯中AIBN存在下，二硅烷1a-d在二丙酮-D-葡萄糖还原黄药2中的反应活性(条目2-5)。二硅烷1a、1b和1d表现出很好的反应活性，而二硅烷1c表现出中等的反应活性，如表1所示。因此，二硅烷1a、1b和1d是脱氧还原黄药2的最有效的试剂。然而，二硅烷1a的制备比二硅烷1b-d的制备简单和实用得多。因此，二硅烷1a被用于从叔醇和仲醇以及糖化合物中衍生的其他黄药2的脱氧还原，以获得相应的还原产物，尽管来自伯醇十三醇的黄药的相同反应以中等的产率得到还原产物(条目15)。也可以使用咪唑硫代羰基来代替甲基二硫代碳酸酯(条目6和13)。从环境角度看，本自由基反应是在乙酸乙酯中进行的。然而，对苯中的黄药进行相同的处理，得到相应的还原产物
Deoxygenation reactions of hydroxy groups in carbohydrates, nucleosides, and antibiotics are very important due to their functional conversion. Today, the most effective and practical deoxygenation method of hydroxy groups is the Barton-McCombie reaction, which is the reaction of xanthates with a tributyltin hydride/AIBN or tributyltin hydride/Et3B system1 or, recently, phenylsilane or diphenylsilane in the presence of peroxide or Et3B, 2 trialkylsilane in the presence of peroxide/thiol (polarity reversal catalyst), 3 5, 10-dihydrosilanthrene/AIBN, 4 tris (trimethylsilyl) silane/AIBN, 5 dibutylphosphine oxide/AIBN or Et3B, 6 or phosphine-borane/AIBN. 7 The Barton-McCombie reaction and the modified Barton-McCombie reaction with alternative reagents have found widespread use in organic synthesis. However, it is well-known that there are several problems in the use of tributyltin hydride, such as toxicity and disposal, workup, and complete removal of the tin species from the products. Phenylsilane, diphenylsilane, and dibutylphosphine oxide are not so reactive, though these compounds are much less toxic than the tin compound. Moreover, these systems are limited to the deoxygenation reaction. To our knowledge, only a few reports for the intermolecular addition reaction of sugar xanthate to electron deficient olefins with tributyltin hydride in moderate yields have been made. 8 Recently, we have reported the utilization of tetraaryl disilanes, which are air-stable crystals, for three types of radical reactions with alkyl bromides, such as reduction, reductive addition to olefins, and alkylation of heteroaromatic bases. 9 Here, as part of our program to develop the synthetic use of tetraaryl disilanes for organic synthesis as an environmentally benign system, we would like to report a new deoxygenative formation of alkyl radicals from alcohols via xanthates, and their reduction to the corresponding hydrocarbons, reductive addition to an activated olefin, and alkylation of heteroaromatic bases, with tetraphenyldisilane as shown in Figure 1. At first, reactivities of disilanes 1a-d in the reduction of xanthate 2 derived from diacetone-D-glucose, in the presence of AIBN in ethyl acetate were studied (entries 2-5). Disilanes 1a, 1b, and 1d showed excellent reactivity, while disilane 1c showed moderate reactivity as shown in Table 1. Thus, disilanes 1a, 1b, and 1d are the most effective reagent for the deoxygenative reduction of xanthates 2. However, the preparation of disilane 1a is much easier and more practical than that of disilanes 1b-d. Thus, disilane 1a was used for the deoxygenative reduction of other xanthates 2, which were derived from tertiary and secondary alcohols, and sugar compounds, to give the corresponding reduction products in good yields, though the same reaction of xanthate derived from tridecanol, a primary alcohol, gave the reduction product in moderate yield (entry 15). An imidazole thiocarbonyl group can be also used instead of a methyl dithiocarbonate group (entries 6 and 13). The present radical reaction was carried out in ethyl acetate from the environmental point of view. However, the same treatment of xanthates in benzene gave the corresponding reduction product in