Heck arylation of allylic alcohols in molten salts (original) (raw)
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The Heck-type arylation of allylic alcohols with arenediazonium salts
Journal of Organometallic Chemistry, 2005
The Heck coupling of ArN 2 BF 4 with secondary allylic alcohols, carried out in methanol using Pd(dba) 2 as catalyst without extra ligands and base, leads to the corresponding b-arylated carbonyl compounds. Such conditions afford arylated acetals from primary allylic alcohols.
Double Arylation of Allyl Alcohol via a One-Pot Heck Arylation–Isomerization–Acylation Cascade
Organic Letters, 2011
A one-pot, two-step catalytic protocol has been developed. A regioselective Heck coupling between aryl bromides and allyl alcohol leads to the generation of arylated allyl alcohols that in situ isomerize to give aldehydes, which then undergo an acylation reaction with a second aryl bromide. A variety of aryl bromides can be employed in both the initial Heck reaction and the acylation, providing easy access to a wide variety of substituted dihydrochalcones.
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.
Pd-catalyzed Heck reactions of aryl bromides with 1,2-diarylethenes
Journal of the Brazilian Chemical Society, 2011
Um sistema catalítico composto por Pd(OAc) 2 e P(o-tol) 3 foi aplicado na reação de Heck entre brometos de arila e diariletenos. Utilizando-se K 2 CO 3 como base e DMF como solvente, olefinas triarilsubstituídas foram obtidas com rendimentos de bons a excelentes. Brometos de arila com substituintes eletroretiradores foram menos ativos para a reação de acoplamento Heck e levaram à formação de produto de homoacoplamento em quantidades substanciais, indicando que a adição oxidativa não deve ser a etapa lenta da reação. A presença de substituintes no diarileteno afetou drasticamente a seletividade da reação. Realizou-se também a dupla arilação do estireno, levando diretamente à olefina triarilsubstituída, com rendimento de 73%. A catalytic system composed of Pd(OAc) 2 and P(o-tol) 3 was found to be effective for the Heck reaction of aryl bromides with diarylethylenes. Using K 2 CO 3 as a base and DMF as a solvent, trisubstituted olefins were obtained in good to excellent yields. Aryl bromides containing an electron-withdrawing group in para position were less reactive for the Heck coupling reaction and gave substantial amount of homocoupling by-product suggesting that oxidative addition is not the rate-determining step. Electron withdrawing group substituent in the para position of stilbene affects the regioselectivity of the reaction. In this case, the phenyl group from the Ph-Pd complex migrates preferentially to the same carbon of the double bond to which the phenyl is bonded. Finally, a one pot sequential double Heck arylation of styrene was performed, giving trisubstituted olefin with an overall yield of 73%.
Examination of Ligand Effects in the Heck Arylation Reaction
Tetrahedron, 2000
AbstractÐThe Heck arylation reaction between aryl bromide and iodide with methyl acrylate was evaluated. A new class of ligands, R±N(CH 2 CH 2 PPh 2 ) 2 , is compared with conventional monodentate and bidentate ligands, and was found to confer greater catalyst stability. The nitrogen substituent (R) has a noticeable effect on the rate of the turnover. We believe this is the ®rst report of the application of such hemilabile ligands in Heck arylation chemistry. q
Base directed palladium catalysed Heck arylation of acrolein diethyl acetal in water
Applied Catalysis A: General, 2014
The selective Heck arylation of acrolein diethyl acetal catalysed by [Pd(NH 3 ) 4 ]Cl 2 in the presence of RAME--CD in water as solvent is described. Depending on the base (i.e. NaOAc or HN(i-Pr) 2 ) good to high selectivity's towards, respectively, the cinnamaldehydes 2 or the 3-arylpropionic esters 1 were achieved. The results support that depending on the base different palladium intermediate complexes are formed. Using NaOAc, {[ArPdX(H 2 O) 2 ]} complex is preferentially generated giving the cinnamaldehyde 2. On the other hand, in the presence of HN(i-Pr) 2 , a L-type ligand, [ArPdX(HN(i-Pr) 2 (H 2 O)] or [ArPdX(HN(i-Pr) 2 (HN(i-Pr) 2 )] will be generated leading to the formation of the 3-arylpropionic ester 1. For the last, coordinated amine participates very probably to the formation of the esters through intramolecular syn -H elimination.
Journal of Molecular …, 2008
Regioselective Heck arylation of ␣-substituted allylic alcohols by aryl bromides was achieved by Pd-DPPP catalysis in ionic liquids, affording a /␥ ratio of up to 78/22 in the case of the coupling of 1-bromonaphthalene with but-1-en-3-ol. In addition to the effects of both ligands and reaction media, the regiocontrol toward the formation of branched products was significantly affected by the steric properties of allylic alcohols; with the increasing bulkiness of the substituent on allylic alcohol, the /␥ regioselectivity decreased. For comparison, arylation by aryl triflates in a molecular solvent was also demonstrated, which showed the same trend in regioselectivity.
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.
ChemInform, 2006
Through the use of [PdCl(C 3 H 5 )] 2 /cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane as a catalyst, a range of aryl bromides undergoes Heck reaction using 2-or 3-subtituted allylic alcohols. With these sterically congested alkenes, the selective formation of b-aryl ketones was observed when appropriate reaction conditions were used. The influence of the functional group on the aryl bromide and of the base on the selectivity is remarkable. With several substrates, much higher selectivities were obtained using NaHCO 3 instead of K 2 CO 3 as base. Furthermore, this catalyst can be used at low loading with several substrates. q
Advanced Synthesis & Catalysis, 2007
A 4-hydroxyacetophenone oxime-derived palladacycle catalyzes the Mizoroki-Heck reaction of allyl alcohols with aryl iodides, bromides, and chlorides in aqueous and organic solvents. The reaction takes place in the presence of dicyclohexylmethylamine or cesium carbonate as bases, the addition of tetrabutylammonium bromide (TBAB) as additive for aryl bromides and chlorides being necessary. Under these reaction conditions, b-arylated aldehydes and ketones are mainly obtained using a rather low loading of palladium (0.1-1 mol %). Similar catalytic activity is shown by a Kaiser oxime resin-derived palladacycle, which allows one to perform recycling and reusing experiments with low Pd leaching. The high regio-and chemoselectivity observed supported that these palladacycles, working as a source of Pd(0) species, operates mainly through a neutral mechanism. This methodology has been applied to the synthesis of important b-arylated carbonyl compounds, such as 4-phenylbutan-2-one, 4-(4-hydroxyphenyl)butan-2-one, dihydrochalcones, the anti-inflamatory nabumetone, and the fragance blilial . g-Arylation is observed in the reactions of allyl alcohol and but-3-en-2-ol with 2-iodoaniline giving mainly the corresponding quinolines. The same tendency is observed in the case of 1,1-dimethylallyl alcohol affording either g-arylated alcohols or (E)-1-arylisoprenes.