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Stereocontrol of Novel Radical Reactions

新型自由基反应的立体控制

基本信息

批准号：
10208208
负责人：
OSHIMA Koichiro
金额：
$ 20.86万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

1. Tri(2-furyl)germane in the presence of Et_3B adds to alkenes efficiently. The addition of tri(2-furyl)germane to silyl enolates followed by elimination of germyl and siloxy moieties provides a new route for the conversion of ketones into alkenes.2. A facile coupling reaction between arylmagnesium compounds and THF by an iodoalkane-EtMgBr system provides 2-aryltetrahydrofurans. In addition, treatment of allyl β-iodoacetals with ethylmagnesium bromide in DME provides tetrahydrofuranylmethylmagnesium compounds.3. Schwartz reagent is an efficient radical chain carrier for the reduction of organic halides in the presence of triethylborane. Reductive radical cyclization of halo acetals with Cp_2Zr(H)Cl provides the cyclized products in good to excellent yields. Reaction employing a catalytic amount of Cp_2ZrCl_2 combined with Red-Al and triethylborane is also successful.4. Treatment of organic halides with phosphinic acid in aqueous ethanol in the presence of a radical initiator and a base yields the corresponding reduced products in high yields. In addition, deuterated phosphinic acid is an efficient chain carrier for the radical deuteration of organic halides.5. Atom transfer radical cyclization of allyl iodoacetate is much more efficient in water than in benzene. Ab initio calculation was conducted to reveal the origin of the solvent effect of water in the cyclization of allyl iodoacetate.6. Stereoselective carboxylation of vinyl halides to give α,β-unsaturated acids could be achieved by two-electron reduction of vinyl bromides in the presence of Ni(II) catalyst and by two-electron reduction of vinyl triflates using an electrochemical method. As one of such studies, we also developed a new and convenient method for a stereoselective synthesis of (E)- and (Z)-vinyl halides by using microwave irradiation.

1. 三(2-呋喃基)锗烷在 Et_3B 存在下有效加成烯烃。将三(2-呋喃基)锗烷加成到硅基烯醇化物上，然后消除甲硅烷基和硅氧基部分，为酮转化为烯烃提供了一条新途径。2．芳基镁化合物和 THF 之间通过碘代烷烃-EtMgBr 系统进行简单的偶联反应，得到 2-芳基四氢呋喃。此外，在DME中用乙基溴化镁处理烯丙基β-碘缩醛，得到四氢呋喃基甲基镁化合物。 3． Schwartz 试剂是一种有效的自由基链载体，用于在三乙基硼烷存在下还原有机卤化物。用 Cp_2Zr(H)Cl 进行卤代缩醛的还原自由基环化，可提供良好至优异产率的环化产物。催化量的Cp_2ZrCl_2与红铝和三乙基硼烷的反应也取得了成功。 4．在自由基引发剂和碱的存在下，用次膦酸在乙醇水溶液中处理有机卤化物，以高产率产生相应的还原产物。此外，氘代次膦酸是有机卤化物自由基氘化的有效链载体。5．碘乙酸烯丙酯的原子转移自由基环化在水中比在苯中更有效。从头计算揭示了碘乙酸烯丙酯环化过程中水溶剂效应的根源。 6．卤乙烯的立体选择性羧化生成α,β-不饱和酸可以通过在Ni(II)催化剂存在下溴乙烯的双电子还原和使用电化学方法的三氟甲磺酸乙烯酯的双电子还原来实现。作为此类研究之一，我们还开发了一种利用微波辐射立体选择性合成（E）-和（Z）-乙烯基卤化物的新且便捷的方法。