Synthesis of novel room temperature chiral ionic liquids: application as reaction media for the heck arylation of aza-endocyclic acrylates (original) (raw)
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Ionic Liquid-Promoted, Highly Regioselective Heck Arylation of Electron-Rich Olefins by Aryl Halides
Journal of the American Chemical Society, 2005
Palladium-catalyzed regioselective Heck arylation of the electron-rich olefins, vinyl ethers 1ad, enamides 1e-g, and allyltrimethylsilane 1h, has been accomplished in imidazolium ionic liquids with a wide range of aryl bromides and iodides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeded with high efficiency and remarkable regioselectivity without the need for costly or toxic halide scavengers, leading exclusively to substitution by aryl groups of diverse electronic and steric properties at the olefinic carbon R to the heteroatom of 1a-g and to the heteroatom of 1h. In contrast, the arylation reaction in molecular solvents led to mixtures of regioisomers under similar conditions. Several lines of evidence point to the unique regiocontrol stemming from the ionic environment provided by the ionic liquid that alters the reaction pathway. The chemistry provides a simple, effective method for preparing branched, arylated olefins and contributes to the extension of Heck reaction to a wider range of substrates.
European Journal of Organic Chemistry, 2007
Herein we report the studies of Heck alkynylation (copper-free Sonogashira) with aryl halides (I, Br, Cl) employing various metallic precursors, tertiary phosphanes and bases in [BMIM][BF4] as the solvent. As a result, we provide the first method that allows the coupling of a large array of substrates, either activated or deactivated bromides in an ionic liquid. Furthermore, the system of highest efficiency is unexpectedly the simplest and cheaper combination that employs [Pd(η3-C3H5)Cl]2/PPh3 at only a 1 mol-% loading with pyrrolidine as the base and in the absence of a copper salt. The coupling of sterically and electronically deactivated bromides bearing different functional groups to aryl- and alkyl acetylenes, as well as the possibility of recycling, make these results of high interest to the future development of Heck- and Sonogashira-type reactions in ionic liquids.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Arenediazonium o-Benzenedisulfonimides as Efficient Reagents for Heck-Type Arylation Reactions
ChemInform, 2006
Arenediazonium o-benzenedisulfonimides can be used as new and efficient reagents for Heck-type arylation reactions of some common substrates containing C-C multiple bonds, namely ethyl acrylate, acrylic acid, acroleyne, styrene and cyclopentene. The reactions were carried out in an organic solvent, in the presence of Pd(OAc) 2 as pre-catalyst, and gave rise to arylated products, for example, ethyl cinnamates, cinnamic acids, cinnamic aldehydes and stilbenes, possessing an (E)-configuration, and 1-arylcyclopentenes, in good to excellent yields. It is noteworthy that all the reactions led to the recovery, in greater than 80% yield, of o-benzenedisulfonimide, recyclable for the preparation of other diazonium salts. q
Journal of Molecular …, 2007
γ-Arylated γ,δ-unsaturated ketones have been prepared in good to excellent yields via the Pd-catalyzed Heck arylation of an electron-rich olefin, 5-hexen-2-one (1), with aryl bromides (2a-2l) in the ionic liquid [bmim][BF 4 ]. The reaction is highly regioselective, leading predominantly to branched, γ-arylated products with Pd-DPPP [DPPP = 1,3-bis(diphenylphosphino)propane] catalysis. However, the choice of ligand is found to be crucial for regiocontrol; a change of ligand from DPPP to 1,1-bis(diphenylphosphino)ferrocene (DPPF) affords predominantly the (E)-type, δ-arylated γ,δ-unsaturated ketones. The method is simple, effective, and applicable to the coupling of both electron-rich and electron-deficient aryl bromides with no need for any halide scavengers.
Journal of Organometallic Chemistry, 2005
Palladium-catalyzed Heck reactions of the heteroaryl halides, halopyridines, bromoquinoline and bromothiophenes, with the electron-rich olefins vinyl ethers and allyl alcohol were shown to give essentially only the branched olefins in an imidazolium ionic liquid, whereas in molecular solvents a mixture of regioisomers was formed. The method obviates the need for aryl triflates and stoichiometric inorganic salt additives, providing an easy entry to functionalized heteroaromatics incorporating acetyl and 2-allyl alcohol functionalities.
Ionic Liquids and the Heck Coupling Reaction: An Update
Current Organic Chemistry, 2013
In this review update we provide a critical analysis of recent results concerning the use of ionic liquids (ILs) as viable, effective, and environmental friendly media for the Heck reactions (HR). The examples selected illustrate the multifaceted action of ILs as nanoparticles stabilizers, promoters of ligand-assisted HR, promoters of phosphine-free HR, solvent for the Heck-Matsuda reactions employing arenediazonium salts, in the dehydrative Heck olefination, and as charged-tagged pre-catalysts. These selected reports aim at demonstrating the scope and the impact of Ils on new discoveries, as well as to illustrate the new opportunities and challenges they offer for those interested in catalysis and organic synthesis in general.
Heck arylation of allylic alcohols in molten salts
Journal of Organometallic Chemistry, 2001
The Heck coupling of ArX (X =I, Br) with allylic alcohols, carried out at 80 -120°C in molten n-Bu 4 NBr using NaHCO 3 as base and PdCl 2 as catalyst without extra ligands, leads to the corresponding b-arylated carbonyl compounds. After extraction of the organic materials with diethyl ether, the ionic layer can be reused directly.