Palladium-Catalyzed Cross-Coupling Reactions of in Situ Generated Allylindium Reagents with Aryl Halides
作者:Phil Ho Lee、Sun-young Sung、Kooyeon Lee
DOI:10.1021/ol016532h
日期:2001.10.1
[reaction: see text] In situ generated allylindium reagents from the reaction of 1 equiv of indium with 1.5 equiv of allyl halides could be effective cross-coupling partners in palladium-catalyzedcross-couplingreactions to arylhalides. The best results were obtained with 2% Pd(2)dba(3)CHCl(3) and 16% Ph(3)P in the presence of 3 equiv of LiCl in DMF at 100 degrees C.
By using a heterobimetallic catalyst, (CO)4(PEtPh2)W(μ-PPh2)Rh(CO)(PPh3), chemoselective hydroformylation of monosubstituted alkenes proceeds efficiently at room temperature under atmospheric pressure of CO/H2, without affecting functional groups such as disubstituted alkene moieties, aryl and alkenyl iodide moieties, and hydroxy and carboxy groups.
Keynote article. Nickel catalysed coupling of allylamines and boronic acids
作者:Barry M. Trost、Michel D. Spagnol
DOI:10.1039/p19950002083
日期:——
vinyl derivatives, E-isomers couple more efficiently than Z-isomers and both fully retain the geometrical integrity. Methylations preferably employ the boronic esters like 2-methyl-1,3,2-benzodioxaborole or 2-methyl-1,3,2-dioxaborolane rather than methylboronic acid. The stereochemistry of the reaction involves a net inversion with respect to the allylamine. The regioselectivity is a function of ligand
Allylic zirconium reagents that are generated in situ via allylic C-H bond activation of alkenes proved to serve as metal counterparts in nickel-catalyzed cross-coupling reactions.
Cross-Coupling of Aromatic Bromides with Allylic Silanolate Salts
作者:Scott E. Denmark、Nathan S. Werner
DOI:10.1021/ja805951j
日期:2008.12.3
The sodium salts of allyldimethylsilanol and 2-butenyldimethylsilanol undergo palladium-catalyzed cross-coupling with a wide variety of aryl bromides to afford allylated and crotylated arenes. The coupling of both silanolates required extensive optimization to deliver the expected products in high yields. The reaction of the allyldimethylsilanolate takes place at 85 degrees C in 1,2-dimethoxyethane with allylpalladium chloride dimer (2.5 mol %) to afford 73-95% yields of the allylation products. Both electron-rich and sterically hindered bromides reacted smoothly, whereas electron-poor bromides cross-coupled in poor yield because of a secondary isomerization to the 1-propenyl isomer (and subsequent polymerization). The 2-butenyldimethylsilanolate (E/Z, 80:20) required additional optimization to maximize the formation of the branched (gamma-substitution) product. A remarkable influence of added alkenes (dibenzylideneacetone and norbornadiene) led to good selectivities for electron-rich and electron-poor bromides in 40-83% yields. However, bromides containing coordinating groups (particularly in the ortho position) gave lower, and in one case even reversed, selectivity. Configurationally homogeneous (E)-silanolates gave slightly higher gamma-selectivity than the pure (2)-silanolates. A unified mechanistic picture involving initial gamma-transmetalation followed by direct reductive elimination or sigma-pi isomerization can rationalize all of the observed trends.