Organothorium-Catalyzed Hydroalkoxylation/Cyclization of Alkynyl Alcohols. Scope, Mechanism, and Ancillary Ligand Effects
作者:Stephen D. Wobser、Tobin J. Marks
DOI:10.1021/om300881b
日期:2013.5.13
hydroelementation processes, and an ROH/ROD kinetic isotope effect of 0.97(0.02) is observed. The reactivity patterns, kinetics, and activation parameters are consistent with a pathway proceeding via turnover-limiting alkyne insertion into the Th–O bond, with subsequent, rapid Th–C protonolysis, regenerating the initial Th–OR species.
带有酰胺或烷基配体的有机锡鎓络合物对炔醇的高度选择性加氢烷氧基化/环化有活性。底物包括伯醇和仲醇,以及末端和内部炔烃。与强烈结合结扎催化剂如五甲基环戊二烯(CP * = C 5我5)或“限制几何构型催化剂”(CGC =我2的Si(η 5 -Me 4 Ç 5)(吨BUN))在整个反应过程中保持可溶性,与(CGC)Th(NMe 2)2(1)比Cp * 2 Th(CH 2 TMS)具有更高的活性2(2)。使用预催化剂的[(ME 3 Si)的2 N] 2的Th [κ 2 - (Ñ,c ^)-CH 2的Si(CH 3)2 N(森达3()] 3在加入醇的)导致沉淀底物,尽管保留了催化活性。为底物范围1包括伯和仲醇以及终端和内部炔烃。原位11 H NMR光谱监测表明,速率规律在[底物]中为零级,在[催化剂]中为第一级。伯醇和末端炔烃的速度比受空间位阻的对应物要快得多,这表明空间需求占主导地位的是加氢烷氧基化/环化过渡态。周转频率高达49ħ