Highly diastereo and enantioselective [4+2] cycloadditions have been achieved between pyrrolidone-derived cyclic enones and α-haloaldehydes under mild conditions. Relying on extremely reactive in-situ generated chiral N-heterocyclic carbenes, this stereoselective annulation proceeds efficiently even on the gram scale with the catalyst loading as low as 0.025 mol% (250 ppm). A variety of cis-substituted
在温和的条件下,
吡咯烷酮衍生的环状烯酮与α-卤代醛之间实现了高度非对映和对映选择性的[4 + 2]环加成反应。依靠极活泼的原位生成的手性N-杂环卡宾,即使催化剂的克含量低至0.025 mol%(250 ppm),这种立体选择性环氧化反应仍能有效地进行克量级的反应。可以以高达96%的收率和高达> 99%的ee产率生产各种顺式取代的双环二氢
吡喃酮。此外,简单的,廉价的线性醛如ñ -
丙醛可以在非对称环加成直接使用通过低催化剂负载量的氧化性N-杂环卡宾有机催化。该方法可以为医学相关分子的不对称合成提供一种经济实用的方法。