Dimerization and cyclotrimerization of aldehydes: ruthenium catalyzed formation of esters, 1,3,5-trioxanes, and aldol condensation products from aldehydes
Dimerization and cyclotrimerization of aldehydes: ruthenium catalyzed formation of esters, 1,3,5-trioxanes, and aldol condensation products from aldehydes
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DOI：
10.1016/j.molcata.2004.08.046
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发表时间：
2004-12
影响因子：
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通讯作者：
A. Sorkau;Kerstin Schwarzer;C. Wagner;E. Poetsch;D. Steinborn
中科院分区：
文献类型：
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作者：
A. Sorkau;Kerstin Schwarzer;C. Wagner;E. Poetsch;D. Steinborn
[RuCl（SiMe 3）（CO）（PPh 3）2]（1）催化醛RC（O）H二聚生成酯RC（O）OCH 2 R（3）的Tishchenko型反应。具有α-氢原子的醛（R = Me、Et、iPr、iBu）在2天内定量反应（5mol%催化剂，70°C，在C6 D 6中），而不具有α-氢原子的醛（R = tBu、Ph）根本不反应。在苯甲醛（R = Ph）的情况下，[RuCl（O2 CPh）（CO）（PPh 3）2]（4）的良好形状的晶体从反应混合物中沉淀。通过单晶X-射线衍射分析确定了催化剂1和苯甲酸根配合物4的分子结构，分别为四方锥（1）和八面体（4）配合物。以乙醛和丙醛的1：1混合物为原料，发生交叉酯化反应，生成酯RC（O）OCH 2 R ′（3，R/R′ = Me/Me，Et/Et; 5，R/R′ = Me/Et，Et/Me）。在tBuC（O）H的情况下，与RC（O）H（R = Me，Et）发生交叉酯化反应，仅产生两种产物，即对称酯RC（O）OCH 2 R（3，R = Me，Et）和RC（O）OCH 2 tBu（6，R = Me，Et）型交叉产物。如丙醛所示，酯的形成完全被水抑制。由于钌催化剂1是由[RuCl（H）（CO）（PPh 3）3]（2）与H2 CCHSiMe 3反应制得的，因此配合物2也可用作与醛反应的催化剂。它被证明是无活性的，但在H2 CCHSiMe 3（H2 CCHSiMe 3：RC（O）H=1：1）存在下，观察到醛（RCHO）3（7）和羟醛缩合产物RCHCR′C（O）H（8，R=Et，iBu; R′ = R-CH 2）的环三聚体的催化形成。
[RuCl(SiMe3)(CO)(PPh3)2] (1) was found to catalyze dimerization of aldehydes RC(O)H yielding esters RC(O)OCH2R (3) in a Tishchenko type reaction. Aldehydes with α-hydrogen atoms (R = Me, Et, iPr, iBu) reacted quantitatively within 2 days (5mol% catalyst, 70°C in C6D6) whereas those without α-hydrogen atoms (R = tBu, Ph) did not react at all. In the case of benzaldehyde (R = Ph), well shaped crystals of [RuCl(O2CPh)(CO)(PPh3)2] (4) precipitated from the reaction mixture. Molecular structures of catalyst 1 and benzoato complex 4 were established by single-crystal X-ray diffraction analyses exhibiting square pyramidal (1) and octahedral (4) complex, respectively. Using 1:1 mixture of acetaldehyde and propanal a crossed esterification reaction took place forming esters RC(O)OCH2R′ (3, R/R′ = Me/Me, Et/Et; 5, R/R′ = Me/Et, Et/Me). In the case of tBuC(O)H a crossed esterification reaction with RC(O)H (R = Me, Et) took place yielding only two products, namely the symmetrical esters RC(O)OCH2R (3, R = Me, Et) and the crossed products of the type RC(O)OCH2tBu (6, R = Me, Et). As shown with propanal, ester formation is completely suppressed by water. Because ruthenium catalyst 1 was prepared by reaction of [RuCl(H)(CO)(PPh3)3] (2) with H2CCHSiMe3, complex 2 was also used as catalyst in the reaction with aldehydes. It proved to be non-active, but in the presence of H2CCHSiMe3(H2CCHSiMe3:RC(O)H=1:1) catalytic formation of cyclotrimers of aldehydes (RCHO)3(7) and aldol condensation products RCHCR′C(O)H (8, R=Et, iBu; R′ = R−CH2) was observed.