Pd-Catalyzed Decarboxylative Asymmetric Protonation of Sterically Hindered α-Aryl Lactones and Dihydrocoumarins
作者:Jinju James、Ramulu Akula、Patrick J. Guiry
DOI:10.1002/adsc.201800724
日期:2018.8.17
Pd‐catalyzed decarboxylative asymmetric protonation (DAP) has been developed for sterically hindered α‐aryl lactone and dihydrocoumarin substrates. Optimization studies were conducted using δ‐lactone‐ and dihydrocoumarin‐derived α‐aryl, β‐oxo‐allyl esters with 2,4,6‐trimethoxyphenyl as the aryl substituent. In the absence of a chiral P,N‐ligand, (1R,2S)‐(−)ephedrine, a cheap and readily available chiral
钯催化的脱羧不对称质子化(DAP)已开发用于空间受阻的α-芳基内酯和二氢香豆素底物。使用由δ-内酯和二氢香豆素衍生的α-芳基,β-氧代烯丙基酯与2,4,6-三甲氧基苯基作为芳基取代基进行了优化研究。在没有手性P,N-配体的情况下,(1 R,2 S)-(-)麻黄碱(廉价且容易获得的手性质子供体)与内酯和二氢香豆素的对映选择性高达92%ee和88%ee基板。含双邻位的庞大芳基取代基和萘基的对映选择性最高,分别高达92%和86%。提出了立体化学原理来解释不对称诱导的优选含义。