Stereocontrol of Novel Radical Reactions

1. 三（2-呋喃基）日耳曼在Et_3B的存在下能有效地加成烯烃。在硅烯醇酯中加入三（2-呋喃基）日耳曼，然后去除了革耳基和硅氧基，为酮类转化为烯烃提供了一条新的途径。芳基镁化合物与四氢呋喃之间通过碘烷- etmgbr体系进行了简单的偶联反应，产生了2-芳基四氢呋喃。此外，乙基溴化镁在二甲醚中处理烯丙基β-碘缩醛可以得到四氢呋喃基甲基镁化合物。施瓦兹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对晕缩醛进行自由基还原环化反应，可得到收率较高的环化产物。采用催化量的Cp_2ZrCl_2与红铝和三乙基硼烷结合的反应也取得了成功。在自由基引发剂和碱存在下，用膦酸在乙醇水溶液中处理有机卤化物，得到相应的高收率还原产物。此外，氘化膦酸是有机卤化物自由基氘化的有效链载体。碘乙酸烯丙基的原子转移自由基环化在水中比在苯中更有效。通过从头计算揭示了水在碘乙酸烯丙基环化过程中溶剂效应的来源。在Ni（II）催化剂的作用下，溴化乙烯和三氟酸乙烯分别用电化学方法进行双电子还原和双电子还原，可实现卤化乙烯立体选择性羧化生成α，β-不饱和酸。作为其中的一项研究，我们还开发了一种新的、方便的微波辐射立体选择性合成(E)-和(Z)-乙烯基卤化物的方法。

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.