| Research Abstract |
(1) The cross-coupling reaction of arylboronic acid with chloroarenes to give biaryls was carried out in high yields at 70-80ﾟC in the presence of a nickel(0) catalyst and K3P04 (3 equiv) in dioxane or benzene. The nickel(0) catalyst in situ prepared from NiCl2L (L = dppf, 2PR_3) (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_2Me, 4-COMe, 4-NHAc, 4-Me, 4-OMe, 4-NH_2, and 4-Nme_<>. 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.
(2) The cross-coupling reaction of arylboronic acids (1.3 equiv) with aryl intanesufonates was carried out in the presence of a nickel(0) catalyst (3 mol%) and K_3PO_<>nH_<>O (3 equiv). The use of toluene as the solvent and the nickel(0)-dppf
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catalyst prepared from NiCI2(dppf) plus dppf with BuLi were recognized to be the most efficient to achieve both high yields and high selectivity. The reaction can be applied to various electron-deficient and -rich aryl methanesulfonates to give high yields.
(3) The carbonyllative cross-coupling reaction of arylboronic acids with electrophiles (ArI, ArBr, and ArOTf) to yield unsymmetrical biaryl ketones was carried out in anisole at 80ﾟC in the presence of a palladium catalyst and a base. The reaction selectively proceeded under an atmospheric presure of carbon monoxide when PdCl_2(PPh3)_2 (3 mol%)/K_2CO_3 (3 equiv) were used for aryl iodides and PdCI_2(dppf) (3 mol%)/K_2CO_3 (3 equiv)/KI (3 equiv) for the bromides or the triflates. The carbonylation of arylboronic acids with benzyl halides gave aryl benzyl ketones.
(4) The cross-coupling reaction of (RO)_2BB(OR)_2 (RO = methoxo and pinacolato) with aryl triflates to give arylboronates was carried out at 80ﾟC in the presence of PdCl2(dppf) (3 mol%), dppf (3 mol%) and KOAc (3 equiv) in dioxane. The reaction was available with various functional groups such as nitro. cyano, and carbonyl groups.
(5) The rhodium(I)-catalyzed conjugate addition of axyl- or 1-alkenylboronic acids to enones was carried out in high yields at 50ﾟC in an aqueous solvent A combination of (acac)Rh(CO)_2 and dppb was recognized to be highly effective for the addition to and cyclic enones. We report asymmetric 1,4-addition of aryl- and alkenylboronic acids which proceeds with high enantioselectivity in the presence of a chiral phosphine-rhodium catalyst
The addition of aryl- and 1-alkenylboronic acids to aldehydes in an aqueous solution. The insertion of carbonyl groups into transition metal-carbon bonds has not received much attention, but the use transition metals as catalyst may allow addition of organometallics that are otherwise insert, asymmetric addition using a chiral phosphine complex, or reaction in an aqueous phase. Less
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