Stereocontrol of Novel Radical Reactions

1.三（2-呋喃基）锗烷在Et_3B存在下能有效地与烯烃加成。三（2-呋喃基）锗烷加成到烯醇化硅酯上，然后消去甲锗烷基和甲硅烷氧基，为酮转化为烯提供了一条新的途径.芳基镁化合物与四氢呋喃在碘代烷-EtMgBr体系中发生偶联反应，生成2-芳基四氢呋喃。此外，烯丙基β-碘缩醛与乙基溴化镁在DME中处理得到四氢呋喃基甲基镁化合物。Schwartz试剂是一种有效的自由基链载体，在三乙基硼烷存在下，它能还原有机卤化物。卤代缩醛与Cp_2Zr（H）Cl的还原自由基环化反应，环化产物产率较高。采用催化量的Cp_2ZrCl_2与红铝和三乙基硼烷结合的反应也是成功的.在自由基引发剂和碱的存在下，在含水乙醇中用次膦酸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代反应的有效链载体.碘乙酸烯丙酯在水中的原子转移自由基环化反应比在苯中更有效。通过从头计算揭示了碘乙酸烯丙酯环化反应中水的溶剂效应的来源.在Ni（II）催化剂存在下，溴代乙烯基的双电子还原和三氟甲磺酸乙烯基酯的双电子还原可实现卤代乙烯的立体选择性羧化，生成α，β-不饱和酸。作为这方面的研究之一，我们还开发了一种新的和方便的方法，立体选择性合成（E）-和（Z）-卤代乙烯使用微波辐射。

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.