Clean Inversion of Configuration in the Pd-Catalyzed Cross-Coupling of 2-Bromo-1,3-dienes
摘要:
The Pd-catalyzed cross-coupling reaction of 2-bromo-1,3-dienes derived from alkyl aldehydes, especially with Cl2Pd(DPEphos) as a catalyst, proceeds with clean stereoinversion of the Br-bearing C=C bond to produce in high yields and in high stereoselectivity (>/=97-98%) conjugated Z,E dienes of potentially high utility in the synthesis of complex natural products. The observed stereoinversion cannot be readily accommodated by the widely accepted pi-sigma-pi rearrangement mechanism for isomerization of ordinary allylpalladium derivatives.
Silafunctional compounds in organic synthesis. 32. Stereoselective halogenolysis of alkenylsilanes: stereochemical dependence on the coordination state of the leaving silyl groups
Various α-sulfonylcarbanions have been shown to react at low temperature with di- or tri-halogenolithiocarbenoïds, to give 1-mono- or 1,1-di-halogenoalkenes. Bromocarbenoïds gave better results than their chloro-analogues. Reaction of di-bromolithiomethane with α-lithiated sulfones gives a high yield of vinylic bromides, the stereochemistry of which is cleanly E. Evidence is presented that the carbenoïd
Iridium‐Catalyzed Hydrochlorination and Hydrobromination of Alkynes by Shuttle Catalysis
作者:Peng Yu、Alessandro Bismuto、Bill Morandi
DOI:10.1002/anie.201912803
日期:2020.2.10
Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium-catalyzed transfer hydrohalogenation of unactivated alkynes. The use of 4-chlorobutan-2-one or tert-butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents, such as hydrogen halides or acid chlorides, thus largely improving the functional-group
Effect of Solvent and Temperature on the Lithium−Bromine Exchange of Vinyl Bromides: Reactions of <i>n</i>-Butyllithium and <i>t</i>-Butyllithium with (<i>E</i>)-5-Bromo-5-decene
作者:William F. Bailey、Mark R. Luderer、Daniel P. Uccello、Ashley L. Bartelson
DOI:10.1021/jo100303q
日期:2010.4.16
regardless of the solvent composition. Vinyl bromide 1 reacts slowly with n-BuLi at room temperature in a variety of ether and heptane-ether mixtures to afford a mixture of products including significant quantities of recovered starting material. The results of these experiments demonstrate that lithium−bromine exchange between a vinyl bromide and either t-BuLi or n-BuLi at temperatures significantly above