New Syntheses of Highly Reactive and Functional Organometallic Compounds and its Application to Organic Syntheses

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The following results are obtained in this research project.1. Silicon-directed Cyclization of Vinylysilanes : Stereoselective Synthesis of Tetrahydrofurans and TetrahydropyransSilicon-directed stereoselective syn addition of hydroxy group to olefinic double bond occurs intramolecularly in an acid-catalyzed cyclization of vinylsilanes bearing hydroxy group. The cyclization proceeds by stereospecific syn addition of the hydroxy group. Vinylsilanes, (Z)-5-silyl-4-penten-1-ols bearing a substituent on the methylene tether, smoothly undergo the acid-catalyzed cyclization to give trans-2,5-, cis-2,4-, and trans-2,3-disubstituted tetrahydrofurans, respectively, with moderate to high stereoselectivity.2. Acid-Catalyzed Cyclization of Vinylsilanes Bearing an Amino Group. Stereoselective Synthesis of PyrrolidinesIn the presence of an acid catalyst, vinylsilanes bearing an amino group protected by an electron-withdrawing group were smoothly cyclized to 2-(silylmethyl) pyrrolidines. This cyclizat … More ion was utilized for the stereoselective synthesis of 2, n-disubstituted pyrrolidines (n=3-5).3. Unprecedented Manganese-Mediated Reactions : Generation of Non-Stabilized Carbonyl YlidsActivated manganese generates nonstabilized carbonyl ylides from bis (chloromethyl) ethers as a precursor, and using this system with manganese as a reductant, the reactions of the ylides with electron-deficient dipolarophiles can be attained without the direct reduction of dipolarophiles by the reductant.4. Manganese Ate Species : Generation and Reactions with ElectrophilesTrialkylmanganese (II) ate reagents, "R_3MnLi" reacted with iodomethylsulfides to produce thiomethylmanganese reagents, where the manganate serves as a reductant not an alkylation agent.The reductive behavior of trialkylmanganese (II) ate reagents provides aprotocol for the direct generation of a new class of reagents, thiomethylmanganese reagents with structural variety, and the generated thiomethylmanganese reagents reacted with allyl bromides, enones and aldehydes.5. Radical Cyclization of 1,6-Enynes Using Allylstannanes and New Radical Reactions Using Stannyl Enolates as Radical Transfer AgentsIn the presence of AIBN, allyltributylstannanes bearing a radical-stabilizing group at the β-position smoothly reacted with 1,6-enynes to give cyclized products incorporated with the stannyl and allyl groups in moderate to good yields. This cyclization is valuable for the synthesis of highly functionalized 5-membered carbocycles and heterocycles. The reactions with β-cyanoallylstannane formed a certain amount of bicyclo [4.3.0] non-1-enes along with monocyclized products. The radical-initiated reactions of α-halo-esters, -nitriles, and -ketones with stannyl enolates gave the corresponding γ-keto derivatives in moderate to high yields. This homolytic process was applied to the three-component coupling reaction among stannyl enolates, haloalkanes, and electron-deficient alkenes.6. New Method for Introduction of a Silyl Group into α, β-Enones Using a Disilane Catalyzed by a Copper (I) salt.The reaction of a disilane with a Cu (I) salt efficiently induces cleavage of the Si-Si bond to generate a silyl nucleophile in an aprotic polar solvent and its 1,4-addition to α, β-unsaturated enones smoothly proceeds with a catalytic amount of a Cu (I) salt were found. This reaction is successfully applied to hexamethyldisilane to generate a trimethylsilyl nucleophile, hitherto not easily accessible. Less