Palladium-Catalyzed Synthesis of 2,1‘-Disubstituted Tetrahydrofurans from γ-Hydroxy Internal Alkenes. Evidence for Alkene Insertion into a Pd−O Bond and Stereochemical Scrambling via β-Hydride Elimination
作者:Michael B. Hay、John P. Wolfe
DOI:10.1021/ja054754v
日期:2005.11.30
diastereoselectivity in reactions of acyclic internal alkene substrates likely derives from a series of reversible β-hydride elimination and σ-bond rotation processes that occur following a rare intramolecular alkene syn-insertion into an intermediate Pd(Ar)(OR) complex. In addition, these studies shed light on the chemoselectivity of insertion, suggesting that the alkene inserts into the Pd−O bond in preference
γ-羟基内部无环烯烃与芳基溴化物的钯催化反应以良好的收率提供 2,1'-二取代的四氢呋喃,非对映选择性为 3-5:1。带有内部环状烯烃的底物的类似转化以良好的收率提供稠合的双环和螺环四氢呋喃衍生物,并具有出色的非对映选择性 (>20:1)。一系列氘标记实验表明,非环状内部烯烃底物反应中适度的非对映选择性的起源可能源于一系列可逆的 β-氢化物消除和 σ-键旋转过程,这些过程发生在罕见的分子内烯烃合成插入到中间体 Pd(Ar)(OR) 络合物。此外,这些研究阐明了插入的化学选择性,