A mild and efficient protocol for the conversion of carboxylic acids to olefins by a catalytic decarbonylative elimination reaction

A new method for the conversion of aliphatic carboxylic acids to olefins under unprecedented mild conditions is disclosed, wherein the carboxylic acids are converted in situ with pivalic anhydride to the mixed anhydrides, which regioselectively add to a PdCl(2)-DPE-Phos catalyst. At a temperature of only 110 degrees C, smooth decarbonylation and beta-hydride elimination occur, and the corresponding olefins along with CO, CO(2) and pivalic acid are liberated.     

Efficient and Rapid Method for the Oxidation of Electron‐Rich Aromatic Aldehydes to Carboxylic Acids Using Improved Basic Hydrogen Peroxide

An efficient and rapid method for oxidation of electron‐rich aromatic aldehydes to their corresponding carboxylic acids in excellent yields was developed. It is based on the oxidation of methoxy‐substituted benzaldehydes in methanol with an improved aqueous basic hydrogen peroxide system. Benzaldehydes with electron‐withdrawing substituents are oxidized to the corresponding carboxylic acid in excellent yields under mild reaction conditions.     

Palladium-catalyzed highly regioselective and stereoselective decarboxylative arylation of unactivated olefins with aryl carboxylic acids

Palladium(II)-catalyzed highly regioselective and stereoselective decarboxylative arylation of unactivated olefins with aryl carboxylic acids has been developed. This method is applicable to a variety of unactivated olefins, including allylamides, long chain functionalized olefins and purely aliphatic olefins, leads to the formation of linear E-configured products in high yields. Both electron-rich and electron-deficient aryl carboxylic acids are suitable arylation reagents. It was found that the choice of solvent, catalyst precursor and oxidant had an important influence on reaction efficiency. As a co-solvent and ligand, DMSO is critical to catalysis. This chemistry expands the scope of decarboxylative arylation of olefins with aryl carboxylic acids, and provides a rapid access to useful linear arylation products of unactivated olefins.     

高效钴氧化物催化羧酸可控加氢制醇（英文）

羧酸选择加氢是合成醇的重要方法,廉价高效的催化体系仍然在探索中.我们利用地球上储量丰富的钴氧化物作为催化剂,通过控制催化反应过程,进而实现高选择性地催化羧酸加氢制备醇.一系列含有不同官能团的羧酸可以被选择加氢至相应的醇类化合物,反应选择性可以满足工业生产要求.通过一系列的谱学表征以及理论计算,我们证实了钴氧化物在羧酸选择加氢反应中的优选活性位点位为氧化亚钴,从而建立了催化剂与反应活性之间的构效关系,为催化剂的理性设计提供指导.首先,我们选取硬脂酸加氢反应作为模型反应,通过对地球上储量丰富的氧化镍、四氧化三铁和四氧化三钴的催化活性对比发现,四氧化三钴催化剂活性最高,在473 K,2 MPa氢气条件下,反应速率可以达到1.2 mmol/(h·g).对四氧化三钴催化剂进行不同温度的预还原处理,我们发现催化剂的活性得到显著提高,其中573 K还原的样品活性最高,反应速率可以达到7.3 mmol/(h·g),要远远高于贵金属催化剂Pd/C(0.6 mmol/(h·g))和Pt/C(1.8 mmol/(h·g)).XRD结果表明,随着还原处理温度的不断升高,催化剂由四氧化三钴变为氧化亚钴,最终变为金属态的钴.当还原温度为573 K时,催化剂的组成为单一相氧化亚钴.XPS测试结果表明,当还原温度为573 K时,样品中只含有Co~(2+)的信号峰,并且Co/O的比例为1/1,进一步证明样品是纯态的氧化亚钴.从TEM照片中可以发现,在原始的四氧化三钴样品中观察到晶面间距为0.467和0.244 nm,分别对应四氧化三钴的(111)和(311)晶面.而对于573 K还原的样品只观察到一种晶面间距(0.246 nm),对应氧化亚钴的(111)晶面.结合表征手段和硬脂酸催化加氢活性结果,我们得出氧化亚钴是573 K还原样品催化羧酸加氢反应的活性位点.理论计算结果进一步证实了这个实验结论.理论计算结果表明,在氧化亚钴(111)晶面,硬脂酸加氢转换为十八醇是非常快速和高效的,然而,对于氢解C-C键和C-O键,需要耗费更高的能量,能垒约为1.2 e V.因为硬脂酸的吸附远远强于十八醇的吸附,硬脂酸的存在会抑制十八醇氢解形成烯烃的反应,只有当硬脂酸酸完全转化为十八醇,才会发生随后的氢解反应.通过控制催化反应过程,可以实现在氧化亚钴(111)晶面高选择性催化酸加氢至醇,也就是反应控制催化过程.基于氧化亚钴在硬脂酸加氢制备十八醇上的优异催化性能,我们进一步研究了一系列含有不同官能团的羧酸化合物的催化加氢,发现氧化亚钴表现出良好的官能团容忍度,可以实现高效、广谱的酸选择加氢至醇反应.     

Ruthenium-catalyzed oxidative cleavage of olefins to aldehydes.

Three oxidation protocols have been developed to cleave olefins to carbonyl compounds with ruthenium trichloride as catalyst (3.5 mol %). These methods convert olefins that are not fully substituted to aldehydes rather than carboxylic acids. While aryl olefins were cleaved to aromatic aldehydes in excellent yields by using the system of RuCl3-Oxone-NaHCO3 in CH3CN-H2O (1.5:1), aliphatic olefins were converted into alkyl aldehydes with RuCl3-NaIO4 in 1,2-dichloroethane-H2O (1:1) in good to excellent yields. It is noteworthy that terminal aliphatic olefins were cleaved to the corresponding aldehydes in excellent yields by using RuCl3-NaIO4 in CH3CN-H2O (6:1).     

水溶性铑膦配合物催化烯烃氢甲酰化反应研究进展

 水/有机两相体系中水溶性铑膦配合物催化的烯烃氢甲酰化反应由于具有环境友好和催化剂容易分离等优点而受到广泛关注. 其中水溶性催化剂体系已经用于丙烯氢甲酰化反应制备丁醛的工业化生产. 然而, 长链烯烃在含有催化剂的水相中溶解性较差, 反应速率较慢. 综述了有关加速水/有机两相体系中长链烯烃氢甲酰化反应的方法和进展, 包括使用具有表面活性的膦配体, 以及在催化体系中添加环糊精和表面活性剂等促进剂. 另外, 还讨论了有关内烯烃氢甲酰化反应和提高直链醛选择性的方法.     

Domino Rhodium/Palladium‐Catalyzed Dehydrogenation Reactions of Alcohols to Acids by Hydrogen Transfer to Inactivated Alkenes

The combination of the d⁸ Rh^I diolefin amide [Rh(trop₂N)(PPh₃)] (trop₂N=bis(5‐H‐dibenzo[a,d]cyclohepten‐5‐yl)amide) and a palladium heterogeneous catalyst results in the formation of a superior catalyst system for the dehydrogenative coupling of alcohols. The overall process represents a mild and direct method for the synthesis of aromatic and heteroaromatic carboxylic acids for which inactivated olefins can be used as hydrogen acceptors. Allyl alcohols are also applicable to this coupling reaction and provide the corresponding saturated aliphatic carboxylic acids. This transformation has been found to be very efficient in the presence of silica‐supported palladium nanoparticles. The dehydrogenation of benzyl alcohol by the rhodium amide, [Rh]N, follows the well established mechanism of metal–ligand bifunctional catalysis. The resulting amino hydride complex, [RhH]NH, transfers a H₂ molecule to the Pd nanoparticles, which, in turn, deliver hydrogen to the inactivated alkene. Thus a domino catalytic reaction is developed which promotes the reaction R‐CH₂‐OH+NaOH+2 alkene→R‐COONa+2 alkane.     

Pd-catalyzed dearboxylative Heck coupling with dioxygen as the terminal oxidant

Pd-catalyzed decarboxylative Heck coupling of aromatic carboxylic acids with various olefins is developed using O(2) as the terminal oxidant. Enhancement of O(2) pressure leads to improving reaction turnover in this transformation and allows significantly reducing catalyst loading for efficient conversion of electron-rich benzoic acids. A Pd catalyst supported by a carbene ligand enables using electron-deficient benzoic acids as coupling partners.     

无溶剂条件下锰 (Ⅲ)-席夫碱配合物催化过氧化氢氧化醇

 Aliphatic and aromatic alcohols are efficiently oxidized to ketones or carboxylic acids using aqueous hydrogen peroxide as an oxidant in the presence of a Mn(III) Schiff-base complex as a catalyst under solvent-free conditions. The oxidation of alcohols occurred at 50 °C to give the corresponding ketones or carboxylic acids with a yield higher than 60%.     

Phosphine‐ and Hydrogen‐Free: Highly Regioselective Ruthenium‐Catalyzed Hydroaminomethylation of Olefins

A highly regioselective ruthenium‐catalyzed hydroaminomethylation of olefins is reported. Using easily available trirutheniumdodecacarbonyl an efficient sequence consisting of a water‐gas shift reaction, hydroformylation of olefins, with subsequent imine or enamine formation and final reduction is realized. This novel procedure is highly practical (ligand‐free, one pot) and economic (low catalyst loading and inexpensive metal). Bulk industrial as well as functionalized olefins react with various amines to give the corresponding tertiary amines generally in high yields (up to 92 %), excellent regioselectivities (n/iso>99:1), and full chemoselectivity in favor of terminal olefins.     

Organocatalytic Asymmetric Hydrolysis of Epoxides

The hydrolytic ring opening of epoxides is an important biosynthetic transformation and is also applied industrially. We report the first organocatalytic variant of this reaction, exploiting our recently discovered activation of carboxylic acids with chiral phosphoric acids via heterodimerization. The methodology mimics the enzymatic mechanism, which involves an enzyme‐bound carboxylate nucleophile. A newly designed phosphoric acid catalyst displays high stereocontrol in the desymmetrization of meso‐epoxides. The methodology shows wide generality with cyclic, acylic, aromatic, and aliphatic substrates. We also apply our method in the first highly enantioselective anti‐dihydroxylation of simple olefins.     

Electrospray ionization mass spectrometry studies of cyclodextrin‐carboxylate ion inclusion complexes

Aqueous solutions containing simple model aliphatic and alicyclic carboxylic acids (surrogates 1–4) were studied using negative ion electrospray mass spectrometry (ESI‐MS) in the presence and absence of α‐, β‐, and γ‐cyclodextrin. Molecular ions were detected corresponding to the parent carboxylic acids and complexed forms of the carboxylic acids; the latter corresponding to non‐covalent inclusion complexes formed between carboxylic acid and cyclodextrin compounds (e.g., β‐CD, α‐CD, and γ‐CD). The formation of 1:1 non‐covalent inclusion cyclodextrin‐carboxylic complexes and non‐inclusion forms of the cellobiose‐carboxylic acid compounds was also observed. Aqueous solutions of Syncrude‐derived mixtures of aliphatic and alicyclic carboxylic acids (i.e. naphthenic acids; NAs) were similarly studied using ESI‐MS, as outlined above. Molecular ions corresponding to the formation of CD‐NAs inclusion complexes were observed whereas 1:1 non‐inclusion forms of the cellobiose‐NAs complexes were not detected. The ESI‐MS results provide evidence for some measure of inclusion selectivity according to the 'size‐fit' of the host and guest molecules (according to carbon number) and the hydrogen deficiency (z‐series) of the naphthenic acid compounds. The relative abundances of the molecular ions of the CD‐carboxylate anion adducts provide strong support for differing complex stability in aqueous solution. In general, the 1:1 complex stability according to hydrogen deficiency (z‐series) of naphthenic acids may be attributed to the nature of the cavity size of the cyclodextrin host compounds and the relative lipophilicity of the guest. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel palladium(II) complex containing a chelating anionic N-O ligand: efficient carbonylation catalyst

[reaction: see text] A novel palladium(II) complex containing chelating anionic pyridine-2-carboxylato and labile tosylato ligands is a highly efficient catalyst for the carbonylation of organic alcohols and olefins to carboxylic acids/esters. Carbonylation of primary, secondary, and tertiary alcohols as well as linear and functionalized terminal olefins was studied. In all cases remarkable activity and selectivity were observed. The catalyst is stable under reaction conditions even in the absence of excess phosphine ligands.     

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．     

Rhodium fluorapatite catalyst for the synthesis of trisubstituted olefins via cross coupling of Baylis-Hillman adducts and arylboronic acids

Treatment of fluorapatite (prepared by incorporating basic species F(-) in apatite in situ by coprecipitation) with an aqueous solution of RhCl(3) resulted in rhodium-exchanged fluorapatite catalyst (RhFAP), which successfully promoted cross coupling of Baylis-Hillman adducts with arylboronic acids to yield trisubstituted olefins. A variety of arylboronic acids and Baylis-Hillman adducts were converted to the corresponding trisubstituted olefins, demonstrating the versatility of the reaction. The reaction is highly stereoselective. RhFAP was recovered quantitatively by simple filtration and reused with almost consistent activity.     

Silica‐Supported Molybdenum Oxo Alkylidenes: Bridging the Gap between Internal and Terminal Olefin Metathesis

Grafting a molybdenum oxo alkylidene on silica (partially dehydroxylated at 700 °C) affords the first example of a well‐defined silica‐supported Mo oxo alkylidene, which is an analogue of the putative active sites in heterogeneous Mo‐based metathesis catalysts. In contrast to its tungsten analogue, which shows poor activity towards terminal olefins because of the formation of a stable off‐cycle metallacyclobutane intermediate, the Mo catalyst shows high metathesis activity for both terminal and internal olefins that is consistent with the lower stability of Mo metallacyclobutane intermediates. This Mo oxo metathesis catalyst also outperforms its corresponding neutral silica‐supported Mo and W imido analogues.     

Intramolecular Aminoboration of Unfunctionalized Olefins

A direct and catalyst‐free method for the intramolecular aminoboration of unfunctionalized olefins is reported. In the presence of BCl₃ (1 equiv) as the sole boron source, intramolecular aminoboration of sulfonamide derivatives of 4‐penten‐1‐amines, 5‐hexen‐1‐amines, and 2‐allylanilines proceeded readily without the use of any catalyst. The boronic acids obtained after hydrolysis could be converted into the corresponding pinacol borates in a straightforward manner by treatment with pinacol under anhydrous conditions.     

Direct hydrogenation of nitroaromatics and one-pot amidation with carboxylic acids over platinum nanowires

A novel ultrathin platinum nanowire with uniform length and a diameter of 1.5 nm was synthesized by acidic etching of FePt nanowire in methanol. This nanowire was characterized by high‐resolution transmission electron microscopy (HRTEM). X‐ray diffraction (XRD) data indicated that the main plane is (111). The ability of this nanowire to catalyze the heterogeneous hydrogenation of nitroaromatics to give the corresponding amines has been investigated. The catalyst showed satisfactory activity in various solvents under mild conditions and showed excellent stability. The catalytic performance was also evaluated in the one‐pot reduction of nitroaromatics and amidation with carboxylic acids under a hydrogen atmosphere at 100 °C. These methods for the hydrogenation of nitroaromatics and the direct amidation of nitroaromatics with carboxylic acids are simple, economical, and environmentally benign, and have practical advantages for the synthesis of amines and amides without the production of toxic byproducts.     

A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic Acids and Esters

We report herein the use of a dual catalytic system comprising a Lewis base catalyst such as quinuclidin‐3‐ol or 4‐dimethylaminopyridine and a photoredox catalyst to generate carbon radicals from either boronic acids or esters. This system enabled a wide range of alkyl boronic esters and aryl or alkyl boronic acids to react with electron‐deficient olefins via radical addition to efficiently form C−C coupled products in a redox‐neutral fashion. The Lewis base catalyst was shown to form a redox‐active complex with either the boronic esters or the trimeric form of the boronic acids (boroxines) in solution.     

Selective Palladium‐Catalyzed Aminocarbonylation of Olefins to Branched Amides

A general and efficient protocol for iso‐selective aminocarbonylation of olefins with aliphatic amines has been developed for the first time. Key to the success for this process is the use of a specific 2‐phosphino‐substituted pyrrole ligand in the presence of PdX₂ (X=halide) as a pre‐catalyst. Bulk industrial and functionalized olefins react with various aliphatic amines, including amino‐acid derivatives, to give the corresponding branched amides generally in good yields (up to 99 %) and regioselectivities (b/l up to 99:1).