首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
The complex [PdCl2(P-N)] containing the basic and sterically demanding 8-(di-tert-butylphosphinooxy)quinoline ligand (P-N) is a highly efficient catalyst for the coupling of phenylboronic acid with aryl bromides or aryl chlorides. The influence of solvent and base has been investigated, the highest rates being observed at 110 °C in toluene with K2CO3 as the base. With aryl bromides the reaction rates are almost independent on the electronic properties of the para aryl substituents, on the contrary, reduced reaction rates are observed when bulky substituents are present on the substrate. Nevertheless the coupling of 2-bromo-1,3,5-trimethylbenzene with phenylboronic acid can be carried out to completion in 2 h using a catalyst loading of 0.02 mol %. Under optimized reaction conditions, turnover frequencies as high as 1900 h−1 can be obtained in the coupling of 4-chloroacetophenone with phenylboronic acid; lower reaction rates are obtained with substrates bearing EDG substituents on the aryl group.  相似文献   

2.
An efficient method for palladium-catalyzed Suzuki cross-coupling reaction with simultaneous reduction of nitro- to amino-group has been developed. This method allows nitro-substituted aryl halides to readily react with arylboronic acids, to afford aryl substituted aniline in low to excellent yields. The reaction was catalyzed by Pd(OAc)2 (3 mol %) at 150 °C under atmospheric pressure in the presence of K2CO3 (3 equiv) in DMF/H2O (5/1).  相似文献   

3.
This study describes a general palladium-catalyzed cyanation of aryl bromides using K4[Fe(CN)6] as the cyanide surrogate. The reactions can be successfully conducted under mild reaction conditions (at 50 °C) in mixed solvents (water/MeCN = 1:1) without any surfactant additives, and afford the desired aryl nitriles in good-to-excellent yields. Particularly noteworthy is that this system allows the mildest reaction temperature reported so far for palladium-catalyzed cyanation of aryl bromides with K4[Fe(CN)6] source in general. Common functional groups, including keto, aldehyde, free amine, and heterocyclic substrates are compatible under this system. Interestingly, the phosphine ligands bearing -PCy2 moiety, which usually show excellent activity in aryl halide couplings, are found less effective than the corresponding ligands with -PPh2 group.  相似文献   

4.
Diaryliodonium salts are shown to undergo rapid, fluoride-promoted aryl exchange reactions at room temperature in acetonitrile. Aryl exchange is shown to be exquisitely sensitive to the concentration of fluoride ion in solution; fast exchange is observed as the fluoride concentration approaches a stoichiometric amount at 50 mM substrate concentration. The reaction is slowed, but not halted if benzene is the solvent, indicating that free fluoride ion or a four-coordinate anionic I(III) species may be responsible for the exchange. The fluoride-promoted aryl exchange reaction is general and allows direct measurement of the relative stabilities of diaryliodonium salts featuring different aryl substituents. The aryl exchange reaction may be of practical use for the preparation of hitherto inaccessible diaryliodonium salts, thus it also has implications for labeling radiotracers for molecular imaging with 18F-fluoride (t1/2 = 109.7 min).  相似文献   

5.
The atom-efficient cross-coupling reaction of sodium tetraarylborates with aryl iodides and bromides was reported. The reaction can be performed directly using a catalytic system composed of palladium chloride, sodium carbonate and methanol (PdCl2/Na2CO3/MeOH) under heat-free conditions at room temperature in an open air conditions. The reactions carried out in an atom-efficient way as 4 equiv of aryl halides coupled effectively with 1 equiv of sodium tetraarylborates to furnish 4 equiv of the corresponding functionalized biaryls in good to excellent yields.  相似文献   

6.
Sonogashira coupling with aqueous ammonia is tolerable for the reaction of aryl iodides or terminal alkynes bearing an azobenzene group. The reaction of (4-heptyloxyphenyl)ethyne with (4-heptyloxyphenyl)-(4-iodophenyl)diazene in the presence of 1 mol% of PdCl2(PPh3)2, 2 mol% of CuI, and 2 equiv of 0.5 M aqueous ammonia gives the corresponding azotolane in 87% isolated yield after stirring at room temperature for 15 h.  相似文献   

7.
This report describes the fluoride-mediated homocoupling of aryl iodides and bromides catalyzed by palladium(0). This coupling protocol is tolerant of electron-donating and electron-withdrawing substitutents on the aryl halide, as well as ortho substitution. Optimum reaction conditions entail 10 mol% Pd(dba)2, 3 equiv of tetrabutyl ammonium fluoride (TBAF) in DMF at 90 °C.  相似文献   

8.
An efficient copper-catalyzed cross-coupling of aryl iodides with aryl acetylenes under microwave irradiation is described. The reaction proceeds under microwave heating with 10 mol % CuI and 2 equiv Cs2CO3 in 43-87% yields.  相似文献   

9.
The general procedure for the rhodium-catalyzed cross-coupling of thiols with aryl iodides is described. The catalytic system consists of 5 mol % of [RhCl(cod)]2 and 10 mol % of PPh3 as a ligand. A variety of aryl iodides reacted with thiols, giving aryl thioethers in good to excellent yields. It is important to note that the deactivated aryl iodides such as 4-iodoanisole is worked smoothly to provide the corresponding aryl thioethers in excellent yields. Functional groups such as free-amines, chloro, are all tolerated under the employed reaction conditions.  相似文献   

10.
A series of air- and moisture-stable Ni(II)-(σ-aryl) complexes, Ni(PPh3)2(aryl)X (X = Cl, Br), were employed as catalyst precursors in the Ni-catalyzed Suzuki cross-coupling reaction. These pre-catalysts easily form the catalytically active Ni(0) species in situ without the need of additional reducing agents. A general catalytic system involving Ni(PPh3)2(1-naph)Cl and PPh3 proved to be highly effective for the Suzuki reaction of aryl chlorides under mild conditions (at 60 °C in THF in the presence of K2CO3 as the base).  相似文献   

11.
N-Amido imidazolium salt was employed as a ligand in the palladium-catalyzed cross-coupling reaction of aryl halides and thiols, and showed good activity in the formation of thioether. The best combination for the coupling with aryl bromides was N-amido imidazolium salt 2 and NaHMDS, and that for the coupling with aryl iodides was N-amido imidazolium salt 1 and KOtBu. The coupling reactions were conducted in the presence of Pd(OAc)2 (1 mol %) in DMSO at 80 °C for 12 h.  相似文献   

12.
A highly efficient copper-catalyzed coupling reaction of aryl iodides and thiobenzoic acid, using 10 mol % of copper iodide, 20 mol % of 1,10-phenanthroline, and iPr2NEt in toluene, was developed. This methodology is applicable to a variety of aryl iodides.  相似文献   

13.
N-(3-Pyridinyl)-substituted secondary and tertiary sulfonamides have been synthesized in good to excellent yields by the reaction of 3-bromopyridine with primary and secondary alkyl and aryl sulfonamides (MeSO2NH2, MeSO2NHMe, TolSO2NH2, TolSO2NHMe, 1,3-propanesultam, and 1,4-butanesultam), catalyzed by CuI (20 mol %) and 1,3-di(pyridin-2-yl)propane-1,3-dione (20 mol %) with K2CO3 (200 mol %) in DMF (0.17 M for ArBr) at 110-120 °C over 36-40 h. 2-Bromopyridine, 4-bromopyridine, and a wide variety of substituted phenyl bromides can also be successfully coupled with sulfonamides under these reaction conditions.  相似文献   

14.
1,4-Disubstituted 1,3-dialkynes were obtained from the one-pot palladium/copper-catalyzed coupling reactions of aryl iodide and propiolic acid. The optimized catalytic system consisted of 5.0 mol % Pd(PPh3)2Cl2, 10 mol % dppb, 10 mol % CuI, 2.4 equiv of DBU, and 1.2 equiv of K2CO3. The coupling reaction was carried out at 30 °C for 6 h and subsequently at 80 °C for 3 h.  相似文献   

15.
Phosphites were employed as ligands in palladium-catalyzed Hiyama coupling reactions. The optimized reaction conditions were equimolar amounts (5 mol % each) of Pd(acac)2 and phosphite 1 in p-xylene at 80 °C with TBAF as an additive. This catalyst system exhibited high activities in the reactions with trimethoxysilylbenzene and aryl bromides that have electron-donating or electron-withdrawing groups. In the case of aryl chlorides, substrates possessing electron-withdrawing groups gave the coupled products in high yields.  相似文献   

16.
Palladium-catalyzed Mizoroki-Heck reaction of allyl aryl ethers with aryl iodides gave aryl cinnamyl ethers using a catalytic amount of Pd(OAc)2 in DMF at 50 °C with phosphine-free hydrazone as a ligand in good yields.  相似文献   

17.
Ming Li 《Tetrahedron letters》2009,50(13):1478-310
An efficient procedure for the direct C-H arylation of electron-poor aromatics such as pyrazine and pyridine with aryl bomides is described. In the presence of catalytic amount of Cy3PAuCl and with the use of t-BuOK as base, pyrazine undergoes the direct C-H arylation with aryl bromides at 100 °C, and the yields of the arylated products depend on the nature of aryl bromides. In the cases of electron-rich aryl bromides used, the arylated pyrazines can be obtained in good to high yields. For electron-poor aryl bromides, the addition of AgBF4 is the crucial point to accelerate the coupling reaction to give the arylated products in moderate yields. Pyridine also reacts with electron-rich aryl bromides catalyzed by Cy3PAuCl to give a mixture of arylated regioisomers in moderate yield. However, in order to realize the direct C-H arylation of pyridine with electron-poor aryl bromides, the addition of silver salt as additive and a milder reaction temperature (60 °C) are required.  相似文献   

18.
We report a mild, convenient, environmentally friendly, and ligand-free synthetic protocol for the cross-coupling reaction of aryl iodides and thiols using 10 mol % CuI with KF/Al2O3 as the base, in DMF at 110 °C. Using this protocol, we have shown that a variety of aryl sulfides can be synthesized in excellent yields from readily available iodides and thiols.  相似文献   

19.
Shao-Nung Chen 《Tetrahedron》2008,64(35):8164-8168
A Pd(NH3)2Cl2/cationic bipyridyl catalytic system catalyzed the cross-coupling reaction of aryl bromides with arylsiloxanes in water under aerobic conditions in the presence of NaOH to afford biaryls in good to high yields. The reaction was performed at 120 °C and the loading amount of catalyst can be as low as 0.001 mol %. After extraction, the residual aqueous phase can be reused several times with only a slight decrease in activity.  相似文献   

20.
Graphene oxide (GO) was functionalized with a N-heterocyclic carbene (NHC) precursor, 3-(3-aminopropyl)-1-methylimidazolium bromide ([APMIm][Br]) for the immobilization of palladium catalyst. The GO-supported NHC precursor (IMGO) formed a stable complex with Pd(OAc)2 (GO–NHC–Pd), which showed excellent catalytic activity and fast reaction kinetics in the aqueous-phase Suzuki reaction of aryl bromides and chlorides at relatively mild conditions (1 h at 50 °C). The GO–NHC–Pd catalyst was reused several times without any loss of its catalytic activity in the Suzuki reaction of aryl bromide.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号