Mechanism of Stereoinduction in Asymmetric Synthesis of Highly Functionalized 1,2-Dihydroquinolines and 2<i>H</i>-1-Benzopyrans via Nonracemic Palladacycles with a Metal-Bonded Stereogenic Carbon
作者:Genliang Lu、Helena C. Malinakova
DOI:10.1021/jo040148r
日期:2004.7.1
auxiliary ligand to the palladium-bonded stereogenic carbon was proposed. A restricted rotation about the palladium-aryl bond in arylpalladium(II) iodo complexes giving rise to atropisomers, as well as the nature of the leaving group (iodide or acetate), were found to play a crucial role in the chirality transfer process. Diastereomerically enriched palladacycles underwent a ligand exchange with triphenylphosphine
为了建立palladacycles的合成效用,制备了具有钯键结合的sp 3-杂化立体碳的稳定的外消旋苯环的azapalladacycle,并通过区域选择性插入将其转化为一系列外消旋的2,3,4-三取代的1,2-二氢喹啉。活化炔烃(RC⋮CCOOEt)。从具有非外消旋旁观者配体((1 R,2 R)-N,N,N ',N '-四甲基-1,2-二氨基环己烷)通过酯烯酸酯的碘化物的分子内置换。明确分配了非对映异构富集的palladacycles中金属键合的立体中心的绝对构型,并系统地研究了立体诱导的效率。在这些实验的基础上,提出了将手性从非外消旋辅助配体转移到与钯键合的立体异构碳上的合理机制。已发现在芳族钯(II)碘配合物中钯-芳基键的旋转受限,导致阻转异构体以及离去基团(碘化物或乙酸盐)的性质在手性转移过程中起着至关重要的作用。H -1-苯并吡喃(四个实例)在32-56%ee中。