Pd-catalyzed intramolecular Heck reaction for the synthesis of 2-methylbenzofurans

A new strategy for the synthesis of 2-Methylbenzofurans via the intramolecular Heck reaction has been developed. This efficient palladium-catalyzed system showed good catalytic activity. Various substituted 2-methylbenzofurans could be afforded in good to excellent yields.     

A novel strategy for the synthesis of 6H-chromeno [4, 3-b] quinoline by intramolecular Heck cyclization

A novel procedure for the synthesis of various derivatives of 6H-chromeno [4, 3-b] quinolines from intramolecular Heck reaction of 2-chloro-3-(phenoxymethyl) quinolines is described in this study. Intramolecular cyclization of N-alkylated indoles was efficiently investigated as well. The reaction is catalyzed by bis (triphenylphosphine) palladium (II) dichloride in acetonitrile at 80 °C.     

The first example of atropisomeric amide-derived P,O-ligands used for an asymmetric Heck reaction

Atropisomeric N,N-diisopropyl 2-diphenylphosphino- and 2-di(tert-butyl)phosphino-1-naphthamides were used, for the first time, as bidentate P,O-ligands for intermolecular asymmetric Heck reactions of 2,3-dihydrofuran with aryl triflates. The reactions were carried out in the presence of 4 mol% Pd(OAc)₂, 8 mol% of the axially chiral ligand, and 3 equiv. of (i-Pr)₂NEt in THF at 60 °C for 3 days. Optically active 2-aryl-2,5-dihydrofurans were obtained as the major products along with the rearranged 2-aryl-2,3-dihydrofurans. Enantioselectivity up to 55.2% ee was obtained for the major product.     

Triaryl phosphine-functionalized N-heterocyclic carbene ligands for Heck reaction

A new type of triaryl phosphine-functionalized imidazolium salts 6 were prepared. Their palladium complexes, generated in situ, were successfully applied in the palladium-catalyzed Heck reaction. Using 1 mol% of Pd(dba)₂ and 1 mol% 6c in the presence of 2 equiv of K₂CO₃ in DMAc has proven to be highly efficient for the coupling of a wide array of aryl bromides and iodides with acrylates in excellent yield. The coupling of 4-bromotoluene with various styrene derivatives catalyzed by Pd/6c complex also gave good results.     

Synthesis of benzofurans in ionic liquid by a PdCl2-catalyzed intramolecular Heck reaction

PdCl₂-catalyzed intramolecular Heck reaction was conducted in ionic liquid, 1-n-butyl-3-methylimidazolium tetraborate ([BMIm] BF₄), substituted benzofurans were obtained in modest to satisfactory yields. The ionic liquid containing Pd catalyst can be used four times with a little loss of activity.     

1,3,2,4-Diazadiphosphetidines as new P-N ligands for palladium-catalyzed Heck reaction in water

1,3,2,4-Diazadiphosphetidine-based phosphazane class have been used as a new generation of heterogeneous bidentate P(III) ligands containing nitrogen for base-free Pd(II) catalyzed C-C bond formation through Heck coupling reaction of aryl iodides, bromides and chlorides in water with styrene, n-butyl acrylate, 1-octene, and cyclohexene. The reactions occur heterogeneously in water and homogenously or partially heterogeneously in appropriate organic solvents. The ligand together with its Pd(0) complex is easily separated by filtration and reused for several runs.     

Reducing agents as components in catalytic systems of the Heck reaction

Using of reducing agents for arylation of alkenes has been found to increase the activity of the catalytic system and allow to avoid the use of traditional tertiary amines as bases in the Heck reaction.     

Facile construction of pyrrolophenanthridone skeleton via a one-pot intramolecular Heck reaction and oxidation

Construction of pyrrolophenanthridone skeleton via a one-pot Pd-catalyzed intramolecular Heck reaction followed by oxidation has been achieved in moderate to good yields. The reaction mechanism has been proposed.     

Catalytic applications of 1,2,4-diazaphospholide-based ruthenium complexes in the Heck reaction

The palladium-catalyzed Heck reaction was effected with two ruthenium complexes bearing unique heterocyclic 1,2,4-diazaphospholide ligands that contain sp²-hybridized phosphorus atoms.     

Highly active Pd(II) catalysts with pyridylbenzoimidazole ligands for the Heck reaction

The air-, and thermo-stable palladium(II) complexes C1-C10 are prepared by the reaction of PdCl₂(CH₃CN)₂ with pyridylbenzoimidazole. With various substituents on the pyridine ring, palladium atom was coordinated by two pyridylbenzoimidazole molecules via nitrogen atoms of benzoimidazole. The structure of complexes C3, C4, C6, and C7 has been confirmed by X-ray diffraction analysis. Without substituents on the pyridine ring, palladium atom was directly coordinated with two nitrogen atoms of pyridine and benzoimidazole nitrogen via intramolecular chelation (C10). These complexes performed the Heck olefination of aryl bromides in a good to high yield under phosphine-free conditions.     

Palladium-catalyzed, asymmetric Baeyer-Villiger oxidation of prochiral cyclobutanones with PHOX ligands

Described in this report is a general method for the conversion of prochiral 3-substituted cyclobutanones to enantioenriched γ-lactones through a palladium-catalyzed Baeyer-Villiger oxidation using phosphinooxazoline ligands in up to 99% yield and 81% ee. Lactones of enantiopurity ≥93% could be obtained through a single recrystallization step. Importantly, 3,3-disubtituted cyclobutanones produced enantioenriched lactones containing a β-quaternary center.     

Investigation on the Coordination Mode of IL-Supported Diols Used as Phosphine-Free Ligands for Palladium Catalyzed Heck Reaction

The coordination mode of IL-supported diols used as phosphine-free ligands for palladium catalyzed Heck reaction has been investigated by tuning their compositions. The difference in coordination of these IL-supported diols with metal Pd in Heck reaction was related to the changes of the cation rings, leading to the different activities of Pd catalyst in the reaction. The experimental results indicated that the activities of Pd catalyst were affected mainly by n-electron density of the cation rings. Compared to pyridinium and piperidinium cations, imidazolium cations showed the best coordination to metal Pd. In the meantime, C-2 hydrogen and the length of alkyl side chains had impacts on the coordination as well.     

Palladium catalyzed Heck reaction of 2-iodoanilines under ligand-free conditions in air

Palladium catalyzed Heck reaction of 2-iodoanilines and acrylate has been developed. The palladium catalyzed Heck reaction of 2-iodoanilines can readily occur in CH₃CN using Pd(OAc)₂ (5.0?mol%) as catalyst, NEt₃ as base under ligand-free conditions. And 2-alkenylanilines were obtained as the cross-coupling products with medium to high yield.     

Desymmetrisation of a diallyl system by intramolecular Heck reaction

The development of a desymmetrising cyclisation of a benzylic diallyl iodide is reported. The final procedure generates a new quaternary chiral centre in greater than 80% yield giving a highly functionalised methylene indan product suitable for further application in synthesis.     

New Heck coupling strategies for the arylation of secondary and tertiary amides via palladium-catalyzed intramolecular cyclization

A new synthetic protocol has been developed for the arylation of secondary and N-alkylated amide Heck precursors by the implementation of the palladium-catalyzed intramolecular Heck reaction strategies.     

Pd(II) complexes of novel phosphine ligands: Synthesis,characterization, and catalytic activities on Heck reaction

Novel phosphine oxides, (((3-methylpyridin-2-yl)amino)methyl)diphenylphosphine oxide (1) and diphenyl((pyrazin-2-ylamino)methyl)phosphine oxide (2), were synthesized and characterized. Phosphines ligands (3 and 4) were obtained by the reduction of 1 and 2 with AlH₃, monitored by ³¹P NMR spectroscopy. Pd(II) complexes of 3 and 4 were synthesized and characterized (5 and 6). The catalytic activity of 5 and 6 was tested on the reaction of styrene with both activated and deactivated aryl bromides in air. The results of the catalytic experiments were discussed through DFT calculations.     

Synthesis of chiral 2-alkyl-8-quinolinyl-oxazoline ligands: reversal of enantioselectivity in the asymmetric palladium-catalyzed allylic alkylation

New chiral 2-alkyl-8-quinolinyl-oxazolines were synthesized from 2-alkyl-8-quinolinecarboxylic acids and enantiomerically pure amino alcohols using a convenient procedure. Enantioselective palladium-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate in the presence of 2-alkyl-8-quinolinyl-oxazolines provided an alkylation product with an opposite configuration compared to those obtained from unsubstituted quinolinyl-oxazoline ligands.     

Palladium N-methylimidazolium supported complexes as efficient catalysts for the Heck reaction

Different N-methylimidazolium supported ligands have been easily synthesized. The palladium complexes derived from those materials can be used for the catalysis of the Heck reaction giving excellent yields, selectivities and very good TON and TOF values. The supported Pd-pincer complexes show an increased stability, and provide a clear improvement in the recovery and reuse for the supported catalysts.     

Palladium nanoparticles: Chemoselective control for reductive Heck with aryl triflates and 2,3-dihydrofuran

The reductive-Heck reaction offers a unique entry to formal Csp²-Csp³ cross-coupling reactions that proceed in the absence of a main group organometallic coupling partner. Consequently, further development of new variants would be transformative. Unfortunately, controlling the relative rates of the organopalladium intermediates has proven difficult with homogenous, single-site Pd catalysts. This work describes a selective reductive Heck reaction catalyzed by Pd-nanoparticles. The reaction works well with electron-deficient aryl triflates at room temperature in the absence of ligands. This work addresses some of the challenges found in the reductive-Heck literature.     

(聚酰胺-胺树枝状大分子)-水杨醛席夫碱钯配合物的Heck反应催化性能研究(英文)

用元素分析、红外光谱、紫外光谱、荧光光谱和核磁等分析手段对合成出的1.0G树枝状大分子-水杨醛席夫碱钯配合物(PAMAMSAPd)进行了表征。用其作为催化剂,研究了碘代苯与丙烯酸在有机溶剂中的偶联反应。对于碘代苯与丙烯酸的偶联反应,最佳反应条件为:惰性气氛,10mmol PhI,nPhI∶nAA∶nEt3N=1∶1.5∶2.5,3.0×10-3g PAMAMSAPd, 4mL DMF和100°C的反应温度。在该条件下,产物肉桂酸的产率可达96.5%。该树枝状大分子配合物是一种无磷、高效和稳定的Heck反应催化剂。且该催化剂经简单的过滤、溶剂洗涤进行回收,重复使用3次,产率仍能达到90.2%。