Stereocontrol of Novel Radical Reactions

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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.