Pd/SiC催化碘代芳烃和芳基硼酸羰化Suzuki偶联反应性能

以高比表面积碳化硅为载体,通过液相还原法制备出Pd/SiC催化剂,并用于催化碘代芳烃和芳基硼酸羰化Suzuki偶联反应.利用X射线衍射、电感耦合等离子体质谱和高分辨透射电子显微镜等对催化剂进行了表征.结果表明, SiC表面的Pd纳米颗粒分散均匀,平均粒径约为2.8 nm.在优化溶剂、碱、压力和温度等反应条件后,发现以3 mmol的K2CO3和10 mL苯甲醚分别为碱和溶剂,1.0 mmol碘苯和1.5 mmol苯硼酸在3 wt% Pd/SiC催化剂存在的条件下,在CO压力为1.0 MPa和100oC下反应8 h即可实现羰化偶联,碘苯转化率为90%,二苯甲酮选择性为99%.并且, Pd/SiC对含有不同官能团的碘代芳烃和芳基硼酸羰化Suzuki偶联反应具有较好的普适性.同时, Pd/SiC也具有较好的稳定性,经5次循环反应后,碘苯转化率从90%降至76%;催化剂活性降低的主要原因是活性组分Pd在有机反应体系中的流失.     

Pd/SiC催化碘代芳烃和芳基硼酸羰化Suzuki偶联反应性能

以高比表面积碳化硅为载体,通过液相还原法制备出Pd/SiC催化剂,并用于催化碘代芳烃和芳基硼酸羰化Suzuki偶联反应.利用X射线衍射、电感耦合等离子体质谱和高分辨透射电子显微镜等对催化剂进行了表征.结果表明, SiC表面的Pd纳米颗粒分散均匀,平均粒径约为2.8 nm.在优化溶剂、碱、压力和温度等反应条件后,发现以3 mmol的K2CO3和10 mL苯甲醚分别为碱和溶剂,1.0 mmol碘苯和1.5 mmol苯硼酸在3 wt% Pd/SiC催化剂存在的条件下,在CO压力为1.0 MPa和100oC下反应8 h即可实现羰化偶联,碘苯转化率为90%,二苯甲酮选择性为99%.并且, Pd/SiC对含有不同官能团的碘代芳烃和芳基硼酸羰化Suzuki偶联反应具有较好的普适性.同时, Pd/SiC也具有较好的稳定性,经5次循环反应后,碘苯转化率从90%降至76%;催化剂活性降低的主要原因是活性组分Pd在有机反应体系中的流失.     

Palladium-catalyzed aminocarbonylation of aryl iodides using aqueous ammonia

Aminocarbonylation of aromatic iodides using aqueous ammonia in toluene has been developed. Various primary aromatic amides have been efficiently synthesized in good to excellent yields in the presence of catalytic quantities of Pd(OAc)₂/CYTOP®292. The usage of aqueous ammonia avoids the handling of two gases in the reaction.     

Highly active and reusable hydrotalcite-supported Pd(0) catalyst for Suzuki coupling reactions of aryl bromides and chlorides

A palladium(0) nanocluster supported on hydrotalcite has been prepared and tested for the Suzuki coupling reaction. The prepared catalyst showed very efficient catalytic activity for cross coupling of iodo- and bromoarenes under very mild reaction conditions, affording >90% yield. Under the optimized reaction conditions, chloroarenenes also showed very good reactivity. Transmission electron microscopic imaging data showed the formation of very small Pd(0)-nanoclusters (d = 2.2 ± 0.5 nm) well dispersed on the support, which enhanced the activity and stability of the catalyst for the Suzuki cross-coupling reaction. This catalytic system offers an easy method of preparation with good activity and reusability up to five cycles.     

Reductive carbonylation of aryl and heteroaryl iodides using Pd(acac)2/dppm as an efficient catalyst

Palladium catalyzed simple and efficient protocol for reductive carbonylation of aryl and heteroaryl compounds has been developed. The formylation of aryl and heteroaryl iodides takes place in the presence of Pd(acac)₂/dppm catalyst at 10 bar pressure of synthetic gas to give the desired aromatic and heteroaromatic aldehydes in good to excellent yields. Easy work-up, stability of the catalyst, low catalyst loading and less reaction time are the advantages of this method.     

Convenient palladium-catalyzed aminocarbonylation of anilines to N-arylbenzamides

The first one-pot diazotization/aminocarbonylation reaction of anilines to benzamides has been developed. In the presence of commercially available palladium acetate/P(o-Tolyl)₃ as the catalyst system without base at low temperature (50 °C) a variety of amides were synthesized in moderate to good yields.     

Microwave-promoted aminocarbonylation of aryl triflates using Mo(CO)6 as a solid CO source

Palladium-catalyzed carbonylations of aryl triflates with a range of nucleophiles using Mo(CO)₆ as a solid CO source were explored. The reactions proceeded smoothly providing moderate to good yields of the corresponding aryl amides, esters, or acylsulfonamides after only 20 min of microwave irradiation. The acyl transfer reagent 4-dimethylaminopyridine was found to promote some of the more difficult transformations.     

Copper- and phosphine-free Sonogashira coupling reactions of aryl iodides catalyzed by an N,N-bis(naphthylideneimino)diethylenetriamine-functionalized polystyrene resin supported Pd(II) complex under aerobic conditions

A polymer-supported palladium(II) N,N-bis(naphthylideneimino)diethylenetriamine complex is found to be a highly active catalyst for Sonogashira coupling reactions. The reactions are performed under copper- and phosphine-free conditions in an air atmosphere. The palladium catalyst is easily separated, and can be reused several times without significant loss in catalytic activity.     

Palladium catalyzed atom-efficient cross-coupling reactions of triarylbismuths with aryl iodides and aryl triflates

The atom-efficient cross-coupling of triarylbismuths with aryl iodides or aryl triflates using catalytic Pd(OAc)₂/PPh₃ and K₃PO₄ as base in DMF at 90 °C to afford the corresponding functionalized biaryls in high yields is reported.     

Pd/C: an efficient and heterogeneous protocol for oxidative carbonylation of diols to cyclic carbonate

The present protocol involves highly efficient and practical approach for the synthesis of cyclic carbonate via oxidative carbonylation of diols, glycerol, and its derivatives using Pd/C as a heterogeneous, inexpensive, and recyclable catalyst. The effect of various reaction parameters, such as solvent, base, time, and temperature was investigated and applied for the synthesis of value added cyclic carbonates in a good to excellent yield within shorter reaction time. The developed catalytic system circumvents the use of ligand and dehydrating agent with an additional advantage of palladium catalyst recovery and reuse for up to four consecutive cycles.     

Rhodium-catalyzed triarylphosphine synthesis via cross-coupling of aryl iodides and acylphosphines

Rhodium(I)-catalyzed C–P cross-coupling reaction with aryl iodides and acylphosphines was disclosed for a straight forward synthesis of triarylphosphines. The acylphosphines were successfully employed as both the phosphorus source and the ligand to the Rh(I) catalyst. The triarylphosphines could be afforded in a yield up to 98% with good toleration of wide functional groups.     

An efficient catalyst system for diaryl ether synthesis from aryl chlorides

The combination of 2-phosphino-substituted N-arylpyrroles or related indoles (cataCXium^®P) and Pd(OAc)₂ allows for efficient cross-coupling reactions of aryl chlorides and phenols to give diaryl ethers. A variety of aryl and heteroaryl chlorides can be coupled with substituted phenols showing unprecedented catalyst turnover numbers.     

Highly efficient Wacker oxidation catalyzed by heterogeneous Pd montmorillonite under acid-free conditions

Palladium-montmorillonite was proven to be highly efficient for the Wacker oxidation of terminal olefins to the corresponding methyl ketones. The catalyst was reusable while maintaining high activity and selectivity.     

Palladium-catalyzed carbonylative synthesis of N-cyanobenzamides from aryl iodides/bromides and cyanamide

A novel and convenient protocol for the synthesis of N-cyanobenzamides starting from readily available aryl halides and cyanamide via palladium-catalyzed aminocarbonylation has been developed. The protocol utilizes Mo(CO)₆ as the CO source or CO(gas) and affords the desired N-cyanobenzamides in moderate to good yields.     

A practical synthesis of highly functionalized aryl nitriles through cyanation of aryl bromides employing heterogeneous Pd/C: in quest of an industrially viable process

Preparation of aryl nitrile 2a through classical Rosenmund-von Braun reaction of aryl bromide 1a resulted in a poor yield (61%) due to a high reaction temperature (165 °C) and a lack of efficient procedure for separating 2a from a large quantity of heavy metal waste (Cu salts). To address these issues, a practical synthesis of multifunctional aryl nitriles through cyanation of aryl bromides has been developed with heterogeneous Pd/C used as the catalyst. Treatment of aryl bromides 1 with Zn(CN)₂ in the presence of Pd/C, Zn, ZnBr₂ and PPh₃ in DMA provided aryl nitriles 2 involving those carrying sterically demanding electron-rich substituent in good yields and in highly reproducible manner. The activity of Pd/C is highly dependent on the properties of the Pd/C. Oxidic thickshell type catalyst Pd/C D5 was found to furnish the highest rate acceleration and yield. The use of heterogeneous Pd/C might anchor and disperse Pd over the solid support of the catalyst, at least in the initial stage of the reaction, to assure the formation of monomeric Pd complex without precipitating to inactive Pd black. The use of a slightly excess of Zn(CN)₂ (0.6 equiv) and air oxidation of phosphine ligand, after end of the reaction, converted Pd species to insoluble phosphine-free Pd cyanides, from which Pd was recovered in high yield through simple filtration followed by usual recovery process involving combustion.     

Pd-catalyzed coupling of aryl iodides with triarylbismuths as atom-economic multi-coupling organometallic nucleophiles under mild conditions

The facile cross-coupling reactivity of triarylbismuth compounds with aryl iodides was achieved under mild heating conditions. The established catalytic protocol using Pd(OAc)₂(Cy₂NH)₂ system exhibited high coupling reactivity with a variety of triarylbismuth and aryl iodide compounds under mild conditions. These coupling reactions were completed in short reaction time affording good to high yields of functionalized biaryl products. The studies of multi-coupling reactions with tris(4-iodophenyl)amine, 8 also furnished moderate to good yields of coupled products, 8a-8f.     

Alkoxycarbonylation of aryl iodides catalyzed by Pd with a thiourea type ligand under balloon pressure of CO

Palladium-catalyzed alkoxycarbonylation of aryl iodides with a thiourea-oxazoline type ligand has been achieved under mild conditions. Various functional groups were tolerated and the yields were from moderate to excellent.     

Efficient hydroxycarbonylation of aryl iodides using recoverable and reusable carbon aerogels doped with palladium nanoparticles as catalyst

Electron-rich and electron-poor aryl iodides are converted, in high to excellent yields, into the corresponding carboxylic acids through a hydroxycarboxylation reaction catalyzed by a recoverable and reusable phosphine free palladium-carbon aerogel catalyst using lithium formate and acetic anhydride as an internal condensed source of carbon monoxide. The catalyst system can be reused several times without any appreciable loss of activity.     

Palladium on carbon as a precatalyst for the Suzuki-Miyuara cross-coupling of aryl chlorides

Palladium on carbon is used as a precatalyst for Suzuki-Miyaura reaction of aryl chlorides and aryl boronic acids. An efficient catalyst system is obtained that allows the reaction of substrates that are difficult to couple under ligand free conditions. This includes electron rich and sterically hindered aryl chlorides as well as electron deficient and sterically hindered boronic acids. We have discovered that the amount of ligand needed to catalyze these reactions can be significantly decreased by incorporating an incubation period. This study also provides valuable insight into the mechanism of the Pd/C-catalyzed Suzuki-Miyaura cross-coupling. For example, mercury poisoning studies provide evidence that the active catalytic species is homogeneous. However, catalyst reuse and low metal contamination indicate that this system retains many of the advantages of a heterogeneous catalyst. From these results, a catalytic cycle is proposed.     

A diphenylphosphinoethane-functionalized polystyrene resin-supported Pd(0) complex as an effective catalyst for copper-free Sonogashira coupling reactions under aerobic conditions

A polymer-supported palladium(0) diphenylphosphinoethane complex was found to be a highly active catalyst for the copper-free Sonogashira coupling reaction of aryl iodides with terminal alkynes, giving excellent yields of products (85-98%) under aerobic conditions.