Z-Selective Intramolecular Horner−Wadsworth−Emmons Reaction for the Synthesis of Macrocyclic Lactones
摘要:
When the substrates (ArO)(2)P(O)CH2CO2-CHO (Ar = Ph, o-t-BuPh) were added to a THF solution containing 3 equiv of NaH at 0 degrees C or NaI-DBU at rt over 1-10 h, the Intramolecular Horner-Wadsworth-Emmons reaction proceeded efficiently to give the 12-18-membered-ring lactones in 69-93% yields with 89-100% Z selectivity. On the other hand, (EtO)(2)P(O)CH2CO2-CHO gave the 13-18-membered-ring lactones in 52-82% yields with 89-99% E selectivity using LiCl-DBU in MeCN or THF.
Divergent Catalysis: Catalytic Asymmetric [4+2] Cycloaddition of Palladium Enolates
作者:Kaylin N. Flesch、Alexander Q. Cusumano、Peng-Jui Chen、Christian Santiago Strong、Stephen R. Sardini、Yun E. Du、Michael D. Bartberger、William A. Goddard、Brian M. Stoltz
DOI:10.1021/jacs.3c02104
日期:2023.5.24
asymmetric decarboxylative [4+2] cycloaddition from a catalytically generated chiral Pd enolate was developed, forging four contiguous stereocenters in a single transformation. This was achieved through a strategy termed divergent catalysis, wherein departure from a known catalytic cycle enables novel reactivity of a targeted intermediate prior to re-entry into the original cycle. Mechanistic studies including
开发了一种由催化生成的手性钯烯醇化物进行的不对称脱羧[4+2]环加成反应,在一次转化中形成四个连续的立体中心。这是通过一种称为发散催化的策略实现的,其中偏离已知的催化循环使得目标中间体在重新进入原始循环之前能够产生新的反应性。包括量子力学计算、Eyring 分析和 KIE 研究在内的机理研究提供了对反应机理的深入了解。