Preparation of benzolactams by Pd(OAc)2-catalyzed direct aromatic carbonylation

We developed a new method for Pd(II)-catalyzed direct aromatic carbonylation in a phosphine-free catalytic system using Pd(OAc)2 and Cu(OAc)2 in an atmosphere of CO gas containing air. The carbonylation proceeded with ortho-palladation, inducing a remarkable site selectivity to afford a variety of five- or six-membered benzolactams from secondary omega-arylalkylamines, such as N-alkylbenzylamines or N-alkylphenethylamines.     

丙酮为溶剂Pd(OAc)2催化的Heck反应研究

研究了无需外加配体、在丙酮溶剂中Pd(OAc)2催化的Heck反应.得到的反应最优结果是:Pd( OAc)2(1 mol%)为催化剂,K2CO3(1.2 equiv.)为添加剂,以廉价易得的丙酮为溶剂,在100℃下各种碘代芳烃(1equiv.)可以顺利地与丙烯酸乙酯、苯乙烯和乙烯环已烷等烯基化合物(2 equiv.)发...     

经由Domino脱HCl/Pd（OAc）2催化的Heck反应合成查尔酮

通过Domino脱HCl/Pd(OAc)2催化的Heck反应实现了β-氯代烷基芳基酮、酯和酰胺与卤代芳烃的交叉偶联反应,高效合成了查尔酮类化合物。利用原位生成烯酮为中间体进行反应的策略,减少副反应的发生,从而提高反应的效率。该方法对各种官能团的容忍性好,为从氯代烷烃出发直接合成查尔酮类化合物提供了一条新途径。     

LiCl-Promoted Pd(II)-catalyzed ortho carbonylation of N,N-dimethylbenzylamines

Palladium-catalyzed highly regioselective carbonylation of substituted N,N-dimethylbenzylamines with the assistance of LiCl was developed. The ortho-functionalized N,N-dimethylbenzylamine was further transformed into ortho-methyl benzoate under mild conditions. These two transformations could be combined into one pot to produce the desired product in moderate yield. Applications of this methodology to synthesize the fragments of variolaric acid were also studied.     

Preparation of benzolactams by Pd(II)-catalyzed carbonylation of N-unprotected arylethylamines

An unprecedented NH(2)-directed Pd(II)-catalytic carbonylation of quaternary aromatic α-amino esters to yield 6-membered benzolactams has been developed. The reaction shows a strong bias to 6-membered lactams over 5-membered ones. The steric hindrance around the amino group seems to be pivotal for the success of the process.     

Pd(OAc)2-catalyzed fluoride-free cross-coupling reactions of arylsiloxanes with aryl bromides in aqueous medium

Mild conditions have been developed to achieve the Pd(OAc)2-catalyzed fluoride-free cross-coupling between the aryl bromides and arylsiloxanes in good to high yields in aqueous medium. The success of the reactions requires the presence of poly(ethylene glycol) (PEG) and 3 equiv of sodium hydroxide. The product was easily separated with ethyl ether extraction, and the catalytic system can be reused eight times with high efficiency.     

Pd(OAc)2-catalyzed oxidative carbonylation of aromatics: synthesis of naphthalenecarboxylic acids

The liquid-phase oxidative carbonylation of aromatics leading to aromatic carboxylic acids is studied to develop new approaches to 2,6-naphthalenedicarboxylic acid (NDA) preparation. It is shown that the catalytic system Pd(OAc)₂/K₂S₂O₈ allows the synthesis of naphthalic anhydride (NAn) by direct oxidative carbonylation of naphthalene under mild conditions (25 °С, 2 atm СО). The subsequent alkaline hydrolysis of NAn and isomerization of the obtained 1,8-naphthalenedicarboxylic acid salt is known to lead to NDA.     

Pd(OAc)(2)-catalyzed oxidative C-H/C-H cross-coupling of electron-deficient polyfluoroarenes with simple arenes

Pd(OAc)(2)-catalyzed intermolecular C-H/C-H cross-coupling reactions between electron-deficient polyfluoroarenes and simple arenes for the synthesis of fluorinated biaryls have been developed. Deuterium-labeling experiments suggested that C-H bond cleavage of the simple arenes rather than the polyfluoroarenes is involved in the rate-limiting step.     

采用醋酸钯/邻菲洛林/脂肪胺催化体系制备丙烯酸乙烯酯

以醋酸钯/邻菲洛林/脂肪胺为催化体系,丙烯酸和乙酸乙烯酯为原料,通过乙烯基交换反应制备丙烯酸乙烯酯。用红外光谱和核磁共振对产物的结构进行了分析和表征;用气相色谱研究了反应的产率;考察了不同种类的共催化剂、反应物配比、不同的脂肪胺对该反应体系催化活性和催化剂稳定性的影响。结果表明,加入脂肪胺能有效稳定钯催化剂,提高反应活性,反应产率达到60%以上。     

Pd(OAc)2-catalyzed orthogonal synthesis of 2-hydroxybenzoates and substituted cyclohexanones from acyclic unsaturated 1,3-carbonyl compounds

A Pd-catalyzed orthogonal synthesis of substituted 2-hydroxybenzoates and substituted cyclohexanones was developed for the first time. The substituted 2-hydroxybenzoates were obtained from acyclic unsaturated 1,3-carbonyl compounds using a combination of catalytic Pd(OAc)₂ and Cu(OAc)₂. On the other hand, the substituted cyclohexanones were produced from similar substrates via catalytic Pd(OAc)₂ and hydrogen chloride. Each transformation was clean, easy to work up, provided the desired compounds in good purities, and did not require column chromatography purification.     

Guanidine/Pd(OAc)2-catalyzed room temperature Suzuki cross-coupling reaction in aqueous media under aerobic conditions

A highly efficient Pd(OAc)2/guanidine aqueous system for the room temperature Suzuki cross-coupling reaction has been developed. The new water-soluble and air-stable catalyst Pd(OAc)2.(1f)2 from Pd(OAc)2 and 1,1,3,3-tetramethyl-2-n-butylguanidine (1f) was synthesized and characterized by X-ray crystallography. In the presence of Pd(OAc)2.(1f)2, coupling of arylboronic acids with a wide range of aryl halides, including aryl iodides, aryl bromides, even activated aryl chlorides, was carried out smoothly in aqueous solvent to afford the cross-coupling products in good to excellent yields and high turnover numbers (TONs) (TONs up to 850,000 for the reaction of 1-iodo-4-nitrobenzene and phenylboronic acid). Furthermore, this mild protocol could tolerate a broad range of functional groups.     

Simple amine/Pd(OAc)(2)-catalyzed suzuki coupling reactions of aryl bromides under mild aerobic conditions

A new palladium catalyst (DAPCy) made from Pd(OAc)(2) and commercially available, inexpensive dicyclohexylamine has been developed for the Suzuki coupling reaction of aryl bromides with boronic acids to give the coupling products in good to high yields. The air-stable catalyst was characterized and well-defined by X-ray crystallography. A catalytic system involving DAPCy in dioxane demonstrates a temperature-dependent reactivity toward aryl bromides with different electronic substituents, and selectively couples electron-deficient aryl bromides with boronic acids over electron-rich ones at room temperature. Another catalytic system employing DAPCy in EtOH provides a general and convenient method to prepare biaryls from aryl bromides and boronic acids with a broad range of functional groups at room temperature and under aerobic conditions.     

Co2(CO)8-catalyzed carbonylation of acetals using N-silylamines

Formaldehyde dialkyl acetals and cyclic acetal, 1,3-dioxolane, are smoothly carbonylated using N-silylamines at 140–160 °C under 70–88 kg cm⁻² CO pressure in the presence of a catalytic amount of Co₂(CO)₈ to give the corresponding 2-alkoxyamides in moderate to good yields. In the carbonylation of formaldehyde dialkyl acetals using N-silylamines, addition of pyridine drastically enhances the catalytic activity.     

Cu（OAc）2 catalyzed Sonogashira cross-coupling reaction in amines

A simple Cu(OAc)_2 catalyzed Sonogashira coupling protocol is presented.It was found that the couplings of a variety of aryl halides with terminal alkynes were conducted smoothly to afford the corresponding desired products in moderate to excellent yields,using Cu(OAc)_2 as the catalyst and Et3N as the solvent.     

Pd(OAc)2/P(cC6H11)3-catalyzed allylation of aryl halides with homoallyl alcohols via retro-allylation

Allylations of aryl halides take place upon treatment of tertiary homoallyl alcohols with aryl halides in the presence of cesium carbonate and a palladium catalyst. The allylation reaction would consist of the following steps: (1) oxidative addition of aryl halide to palladium, (2) ligand exchange between the halide and the homoallyl alcohol affording aryl(homoallyloxy)palladium, (3) retro-allylation of the palladium alkoxide to generate sigma-allyl(aryl)palladium with concomitant liberation of the relevant ketone, and (4) productive reductive elimination. Since the retro-allylation step proceeds in a concerted fashion via a conformationally regulated six-membered cyclic transition state, the allylation reactions are highly regio- and stereospecific when homoallyl alcohols having a substituted allyl group are used. Whereas triarylphosphine is known to serve as a ligand for the palladium-catalyzed allyl transfer reactions, tricyclohexylphosphine proves to significantly expand the scopes of aryl halides to electron-rich aryl chlorides and of homoallyl alcohols to cyclic homoallyl alcohols. The new arylative ring-opening reactions of cyclic homoallyl alcohols allow for the synthesis of ketones having a branched or linear allylarene moiety at the remote terminus in regio- and stereospecific manners.     

Cu(OAc)2-catalyzed N-arylations of sulfoximines with aryl boronic acids

[reaction: see text] A simple and mild copper salt-catalyzed N-arylation of sulfoximines in high yields is reported. Cu(OAc)(2) activates aryl boronic acids for the reaction with NH-sulfoximines without additional base or heating. Furthermore, this new method allows the preparation of N-arylated sulfoximines, which have previously been more difficult to access.     

Pd(OAc)2 promoted bis-N-heterocyclic carbene-catalyzed oxidative transformation of aldehydes

The bis-N-heterocyclic carbene-catalyzed (bis-NHC-catalyzed) oxidative transformation of aldehydes was successfully studied in water under air. The reaction rate increased through the use of Pd(OAc)₂ as an additive. Notably, the catalytic system exhibited good tolerance toward aliphatic and aromatic aldehydes bearing halide and alkyl functional groups. In addition, gram-scale reaction was also tested in this study. The use of water and operational simplicity make this methodology environmentally benign and cost-effective.     

The Real Structure of Pd(OAc)2 in Various Solvents

Pd(OAc)₂ is an extensively utilized palladium source in the palladium initiated transformations either directly or as a catalyst precursor. However, the comprehension of the real structure of Pd(OAc)₂ in solution is still vague. In this work, the structure of palladium acetate in solution was studied in detail by using X-ray absorption fine structure (XAFS) spectroscopy. The results demonstrate that monomer is the main form for Pd(OAc)₂ in the solution of 1,4-dioxane, N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), 1,2-dimethoxyethane (DME), MeCN and dimethyl sulfoxide (DMSO). In addition, Pd(II) could be reduced to Pd(0) in ethanol solution. The structural information in this research will benefit the understanding of the mechanism of Pd(OAc)₂ involved organic reactions.     

Pd(OAc)(2)-catalyzed Domino reactions of 1-chloro-2-haloarenes and 2-haloaryl tosylates with hindered Grignard reagents via palladium-associated arynes

The palladium-associated aryne generation strategy and Pd(OAc)(2)-catalyzed annulative Domino reactions of 1-chloro-2-halobenzenes and 2-haloaryl tosylates with hindered Grignard reagents via palladium-associated arynes are described. The palladium-associated aryne generation strategy described here not only allows the high yield, one-step access to potentially useful substituted fluorenes from readily available 1-chloro-2-halobenzenes and 2-haloaryl tosylates, but may also lead to the development of other tandem reactions based on these readily available ortho leaving group bearing haloarenes. [reaction: see text]     

Pd(OAc)_2/HQ/FePc、Pd(OAc)_2/FePc 催化烯烃氧化合成酮的研究

考察了在乙腈酸性水溶液中Ｐｄ（ＯＡｃ）２／氢醌（ＨＱ）／酞青铁（ＦｅＰｃ）和Ｐｄ（ＯＡｃ）２／ＦｅＰｃ对环己烯、环戊烯、苯乙烯、正癸烯氧化合成相应酮的催化活性．实验结果表明，两类催化体系对环戊烯的酮基化均呈现出较高的催化活性，环戊酮收率可达９８％．在其它烯烃的氧化反应中，三元催化体系Ｐｄ（ＯＡｃ）２／ＨＱ／ＦｅＰｃ的催化活性高于二元的Ｐｄ（ＯＡｃ）２／ＦｅＰｃ．这表明，在Ｗａｃｋｅｒ类催化体系中，电子传递体的作用是很重要的．对催化体系中各组分的作用进行了讨论，并给出了可能的催化作用机理．