Kakiuchi Fumitoshi, Matsuura Yusuke, Kan Shintaro, Chatani Naoto
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan, and PRESTO, JST, 4-1-8 Honcho Kawaguchi, Saitama, Japan.
J Am Chem Soc. 2005 Apr 27;127(16):5936-45. doi: 10.1021/ja043334n.
When the reaction of aromatic ketones with arylboronates (arylboronic acid esters) using RuH(2)(CO)(PPh(3))(3) (3) as a catalyst was conducted in toluene, the corresponding arylation product was obtained in moderate yields. In this case, a nearly equivalent amount of a benzyl alcohol derived from a reduction of an aromatic ketone was also formed. The use of aliphatic ketones, such as pinacolone and acetone, as an additive or a solvent dramatically suppressed the reduction of the aromatic ketones and, as a result, ortho-arylation products were obtained in high yield based on the aromatic ketones. In these reactions, the aliphatic ketone functioned as a scavenger of ortho-hydrogens of the aromatic ketones and the B(OR)(2) moiety of the arylboron compound (HB species). A variety of aromatic ketones, such as acetophenones, acetonaphthones, tetralones, and benzosuberone, could also be used in this coupling reaction. Several arylboronates containing electron-donating (NMe(2), OMe, and Me) and -withdrawing (CF(3) and F) groups were also applicable to this coupling reaction. Intermolecular competitive reaction using pivalophenone-d(0)() and -d(5) and intramolecular competitive reaction using pivalophenone-d(1) were carried out using 3 as a catalyst. The k(H)/k(D) value for the intermolecular competitive reaction was substantially different, compared with intramolecular competitive reaction. This strongly suggests the production of an intermediate where the ketone carbonyl is coordinated to the ruthenium involved in this catalytic reaction. (1)H and (11)B NMR studies using 2'-methylacetophenone, phenylboronate (2), and pinacolone (6) indicate that 6 functions effectively as a scavenger of the HB species.
当使用RuH₂(CO)(PPh₃)₃（3）作为催化剂，使芳香酮与芳基硼酸酯（芳基硼酸酯）在甲苯中反应时，可得到中等产率的相应芳基化产物。在这种情况下，还会形成几乎等量的由芳香酮还原得到的苄醇。使用脂肪族酮，如频哪酮和丙酮，作为添加剂或溶剂，可显著抑制芳香酮的还原，结果，基于芳香酮可高产率地得到邻位芳基化产物。在这些反应中，脂肪族酮起到了芳香酮邻位氢和芳基硼化合物B(OR)₂部分（HB物种）清除剂的作用。多种芳香酮，如苯乙酮、萘乙酮、四氢萘酮和苯并环庚酮，也可用于该偶联反应。几种含有供电子基团（NMe₂、OMe和Me）和吸电子基团（CF₃和F）的芳基硼酸酯也适用于该偶联反应。以3作为催化剂，进行了新戊苯乙酮-d₀和-d₅的分子间竞争反应以及新戊苯乙酮-d₁的分子内竞争反应。与分子内竞争反应相比，分子间竞争反应的k(H)/k(D)值有很大差异。这有力地表明在该催化反应中生成了一种酮羰基与钌配位的中间体。使用2'-甲基苯乙酮、苯基硼酸酯（2）和频哪酮（6）进行的¹H和¹¹B NMR研究表明，6能有效地作为HB物种的清除剂。
