HECK REACTIONS OF ARYL CHLORIDES CATALYZED BY PALLADIUM/TRI-tert-BUTYLPHOSPHINE: (E)-2-METHYL-3-PHENYLACRYLIC ACID BUTYL ESTER AND (E)-4-(2-PHENYLETHENYL)BENZONITRILE
作者:Littke, Adam F.、Fu, Gregory C.、Ober, Michael H.、Denmark, Scott E.
DOI:10.15227/orgsyn.081.0063
日期:——
A Phosphane‐Free Catalyst System for the Heck Arylation of Disubstituted Alkenes: Application to the Synthesis of Trisubstituted Olefins
A new general procedure for the Heck arylation of disubstituted olefins is described. This procedure allows, in many instances, the stereoselective synthesis of trisubstituted olefins. Trisubstituted olefins are easily accessible under mild reaction conditions using a new catalyst system consisting of dicyclohexylamine or methyl-(dicyclohexyl)amine and a phase-transfer catalyst. The choice of base was found to be crucial for the rate and stereoselectivity of the Heck arylation reactions. This method is applicable to the coupling of both electron-deficient and electron-rich aryl halides and displays good stereoselectivity and a high degree: of functional group compatibility. Labeling studies indicate that the source of this selectivity is thermodynamic in nature.
A Versatile Catalyst for Heck Reactions of Aryl Chlorides and Aryl Bromides under Mild Conditions
作者:Adam F. Littke、Gregory C. Fu
DOI:10.1021/ja010988c
日期:2001.7.1
for Heck reactions of arylchlorides and bromides. A sterically and electronically diverse array of aryl bromides, as well as activated arylchlorides, couple with a range of mono- and disubstituted olefins at room temperature, furnishing the arylated product with high E/Z stereoselection. The corresponding reactions of a broad spectrum of electron-neutral and electron-rich arylchlorides proceed at
osmium-catalyzed dihydroxylation has uncovered that electron-deficient olefins are converted into the corresponding diols much more efficiently when the pH of the reaction medium is maintained on the acidic side. Further studies have identified citric acid as the additive of choice, for it allows preparation of very pure diols in yields generally exceeding 90%. As described here, a much wider range of olefin classes