Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Am Chem Soc. 2010 Jul 7;132(26):8862-3. doi: 10.1021/ja1035286.
The first general catalytic enantioselective conjugate addition of cyanide to beta,beta-disubstituted alpha,beta-unsaturated ketones and N-acylpyrroles was developed using a strontium catalyst derived from Sr(O(i)Pr)(2) and new chiral ligand 5. The reaction exhibited excellent enantioselectivity and a wide substrate scope using 0.5-10 mol % catalyst. 1,4-Adducts containing beta-quaternary carbons were exclusively produced over 1,2-adducts. ESI-MS analysis of the strontium catalyst indicated that the active catalyst was a trimetallic Sr/5 = 3:5 complex. The exclusive 1,4-selectivity was partly due to the ability of the strontium complex to promote both a retro-cyanation reaction from the 1,2-adducts and highly enantioselective conjugate cyanation.
首次发展了使用 Sr(O(i)Pr)(2) 和新型手性配体 5 衍生的锶催化剂，实现氰化物对β,β-二取代α,β-不饱和酮和 N-酰基吡咯的首例普适性催化对映选择性共轭加成反应。反应仅生成 1,4-加成产物（β-季碳），表现出极好的对映选择性和广泛的底物范围，催化剂用量仅为 0.5-10 mol%。ESI-MS 分析表明，活性催化剂为三金属 Sr/5 = 3:5 配合物。这种 1,4-选择性部分归因于锶配合物既能促进 1,2-加成物的逆氰化反应，又能高对映选择性地促进共轭氰化反应。
