Activation of Carbon-Carbon Bonds by Soluble Transition Metals

研究了铑（I）催化的环丁酮羰基α位C-C键选择性断裂的合成反应。环丁酮与等摩尔量的（Ph_3P）_3RhCl在甲苯中回流脱羰得到相应的环丙烷。环丙烷的形成表明Rh（I）在初始步骤中经历了插入到羰基碳和α-碳之间的键中。环丁酮的催化脱羰反应也得到了实现。反应的方式和速率在很大程度上取决于铑（I）配合物的配体。当使用在3-位上带有氢原子的环丁酮时，适当选择催化剂体系导致选择性地形成环丙烷或烯烃。考察了配体、氢压、溶剂等反应条件，环己酮氢解反应未能有效进行。其他金属如钌和铱被发现是无效的。我们将继续研究可溶性过渡金属配合物对普通酮的C-C键的选择性断裂。

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.