Activation of Carbon-Carbon Bonds by Soluble Transition Metals

研究了Rh(I)催化的合成转化反应，包括选择性地将C-C键α断裂为环丁酮的羰基。环丁酮与等摩尔量的(Ph_3P)_3RhCl在甲苯中回流时发生脱羰化反应，得到相应的环丙烷。环丙烷的形成表明，Rh(I)在初始步骤中插入了羰基碳和α-碳之间的键。还实现了环丁酮的催化脱羰反应。反应的方式和速度在很大程度上取决于Rh(I)络合物的配体。当使用3位含氢原子的环丁酮时，适当选择催化剂体系可以选择性地生成环丙烷或烯烃。接下来尝试环己酮的氢解反应。考察了配体、氢气压力、溶剂等各种反应条件，环己酮氢解反应不能有效进行。其他金属如Ru和Ir被发现是无效的。我们将继续研究一种可溶的过渡金属络合物选择性断裂普通酮的C-C键。

Rhodium(I)-catalyzed synthetic transformations involving selective breaking of the C-C bond alpha to the carbonyl group of cyclobutanones was studied. Decarbonylation took place on treatment of a cyclobutanone with an equimolar amount of (Ph_3P)_3RhCl at reflux in toluene to afford the corresponding cyclopropane. The formation of the cyclopropane suggests that Rh(I) undergoes an insertion into the bond between the carbonyl carbon and the alpha-carbon in the initial step. Catalytic decarbonylation of cyclobutanone was also achieved. The mode and rate of the reaction depended greatly on the ligands of the rhodium(I) complex. When a cyclobutanone bearing a hydrogen atom at the 3-position was used, appropriate choice of the catalyst system led to the selective formation of either a cyclopropane or an alkene.Hydrogenolysis of cyclohexanone was next attempted. Various reaction conditions including ligands, hydrogen pressure, and solvent were examined, hydrogenolysis of cyclohexanone failed to proceed efficiently. Other metals like ruthenium and iridium were found to be ineffective. We will continue to investigate selective breaking of C-C bonds of ordinary ketones by a soluble transition metal complex.