Asymmetric dihydroxylation of 1-acyloxy-2(E)-alkenylphosphonates with AD-mix reagents. Effects of 1-acyloxy functional groups on the asymmetric dihydroxylation
摘要:
Asymmetric dihydroxylation (AD) of a racemic mixture of 1-acyloxy-2(E)-alkenylphosphonates with AD-mix-alpha or -beta reagents was examined. The kinetic rate of dihydroxylation was highly dependent upon the configuration of the 1-acyloxy functional group as well as the nature of substituents at the 3-position. ?he reaction of a racemic mixture of diethyl (E)-3-phenyl-1-acetyloxy-2-propenylphosphonate with an AD-mix-beta reagent preferentially dihydroxylated the R-enantiomer to leave an unreacted S-enantiomer of high enantiomeric purity. Double diastereoselection of the resolved diethyl 3-phenyl-1-acetyloxy-2(E)-propenylphosphonate in dihydroxylation was also examined. (C) 1997 Elsevier Science Ltd. All rights reserved.
Asymmetric construction of phosphono dihydropyranones from α-ketophosphonates enabled by Pd/chiral isothiourea relay catalysis
作者:Mostafa Sayed、Zhipeng Shi、Zhi-Yong Han、Liu-Zhu Gong
DOI:10.1039/d3ob01267k
日期:——
the synthesis of chiral phosphono dihydropyranones. This approach is enabled by Pd/chiral isothiourea relay catalysis under mild reaction conditions, starting from readily available benzyl bromides, CO, and α-ketophosphonates. The cascade reactioninvolves the generation of a ketene intermediate from Pd-catalyzed carbonylation of benzyl bromide and subsequent chiral Lewis base catalyzed formal [4 +