| Research Abstract |
1. The addition of 9-(alkylthio)-9-borabicyclo[3.3.1]nonane to terminal alkynes was catalyzed by Pd(PPhィイD23ィエD2)ィイD24ィエD2 to produce 9-[(Z)-2-(alkylthio)-1-Alkenyl]-9-BBN derivatives in high yields. The reactions were high regio- and stereoselective, and their conditions were sufficiently mild that a variety of functionalized alkenylborane with defined stereochemistry were readily synthesized.
2. The Transition metal-catalyzed borylation of alkenes, alkynes, and organic electrophiles with B-B compounds was developed for the sysnthesis of organoboronic esters from simple organic substrates. The platinum(0)-catalyzed addition of bis(pinacolato)diboron to either terminal- or internal alkynes to give cis-bis(boryl)alkenes. The addition of diboron to alkenes, 1,3-dienes, 1,2-dienes, α,β-unsaturated ketones, methylenecyclopropanes with a platinum(0) complex gave the corresponding bis(boryl)products.
3. The cross-coupling reaction of diborons with aryl and vinyl halides or triflates, and allyl
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chlorides or acetates was found to yield aryl-, vinyl- and allylboronates in high yields in the presence of a base and a palladium catalyst, which provides the first one step procedure for synthesis of organoboronic esters from organic electrophiles.
4. The cross-coupling reaction of arylboronic acid with chloroarenes and aryl metanesufonates to give biaryls was carried out in high yields at 70-80℃ in the presence of a nickel(0) catalyst and KィイD23ィエD2POィイD24ィエD2 (3 equiv) in dioxane, toluene or benzene. The nickel(0) catalyst in situ prepared from NiClィイD22ィエD2LィイD22ィエD2 (L = dppf, 2PRィイD23ィエD2) (3-10 mol%) and 4 equiv of BuLi at room temperature was recognized to be most effective: The reaction can be applicable to a wide range of chloroarenes having an electron-withdrawing or an electron-donating group such as 4-NC, 4-CHO, 2-or 4-COィイD22ィエD2Me, 4-COMe, 4-NHAc, 4-Me, 4-OMe, 4-NHィイD22ィエD2, and 4-NMeィイD22ィエD2. The Hammett's plot of the substituent effect of chloroarenes revealed that the reaction involves a rate determining oxidative addition of chloroarenes to the nickel(0) complex. The reaction can be applied to various electron-deficient and -rich aryl methanesulfonates to give high yields.
5. The rhodium-catalyzed addition of aryl- and 1-alkenylboronic acids to α,β-unsaturated ketones, aldehydes, esters, and amides gave the conjugate 1,4-addition products in high yields. The Rhodium(I) complexes also catalyzed the 1,2-addition of organoboronic acids to aldehydes or N-sulfonyl aldimines. The efficiency of protocol was demonstrated on the asymmetric addition reactions of organoboronic acids in the presence of a rhodium(acac)/BINAP complex.
6. The stereoselective isomerization of allyl silyl ethers to (E)- or (Z)-silyl enol ethers was carried out in the presence of a cationic iridium(I) catalyst. The complex, prepared in situ by treating [Ir(cod)ィイD22ィエD2]PFィイD26ィエD2/2PPrィイD23ィエD2 with hydrogen, was found to be an excellent catalyst for the isomerization of primary and secondary allyl ethers in high yields. The primary allyl silyl ethers produced (E)-enol ethers and the secondary allyl ethers afforded (Z)-enol ethers with high stereoselectivity, often exceeding 99%. We reported an alternative and direct method for the synthesis of allylboronates using metal-catalyzed isomerization of double bond. The cationic iridium complex obtained via hydrogenation of [Ir(cod)(PPhィイD22ィエD2Me)ィイD22ィエD2]PFィイD26ィエD2 was recognized to be an excellent catalyst for isomerization of various 3-(alkoxy)-1-propenylboronates under mild conditions. Less
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