A ruthenium-catalyzed reaction of aromatic ketones with arylboronates: a new method for the arylation of aromatic compounds via C-H bond cleavage

The ruthenium-catalyzed reaction of aromatic ketones with arylboronic acid esters (arylboronates) gave the ortho arylation product. For this coupling reaction, a RuH2(CO)(PPh3)3 complex exhibited the highest catalytic activity among the complexes screened. Several aromatic ketones, for example, acetophenones, acetonaphthone, alpha-tetralone, and benzosuberone, can be used in this coupling reaction. A variety of arylboronates containing electron-donating (OMe and NMe2) and -withdrawing (F and CF3) groups were found to react with aromatic ketones to give the corresponding aylation products. The corresponding arylboronic acids could be used in this coupling reaction, but the yields were slightly lower, as compared to those of the reaction using the corresponding arylboronates.     

Ruthenium-catalyzed functionalization of aryl carbon-oxygen bonds in aromatic ethers with organoboron compounds

The ruthenium-catalyzed reaction of aryl ethers having a carbonyl group at the ortho position to the ether group with organoboronates (R-B(OCH2CMe2CH2O), R = aryl, alkenyl, and alkyl) resulted in site-selective C-C bond formation. Among the transition metal complexes screened, the RuH2(CO)(PPh3)3 complex showed the highest activity. Several aromatic ketones having methoxy or phenoxy groups at the ortho position can also be used in this coupling reaction. A variety of arylboronates containing electron-donating (NMe2, OMe, methyl, and vinyl) and -withdrawing (F and CF3) groups reacted with methoxy ketones to give the corresponding coupling products in high yields.     

A RuH(2)(CO)(PPh(3))(3)-catalyzed regioselective arylation of aromatic ketones with arylboronates via carbon-hydrogen bond cleavage

When the reaction of aromatic ketones with arylboronates (arylboronic acid esters) using RuH(2)(CO)(PPh(3))(3) (3) as a catalyst was conducted in toluene, the corresponding arylation product was obtained in moderate yields. In this case, a nearly equivalent amount of a benzyl alcohol derived from a reduction of an aromatic ketone was also formed. The use of aliphatic ketones, such as pinacolone and acetone, as an additive or a solvent dramatically suppressed the reduction of the aromatic ketones and, as a result, ortho-arylation products were obtained in high yield based on the aromatic ketones. In these reactions, the aliphatic ketone functioned as a scavenger of ortho-hydrogens of the aromatic ketones and the B(OR)(2) moiety of the arylboron compound (HB species). A variety of aromatic ketones, such as acetophenones, acetonaphthones, tetralones, and benzosuberone, could also be used in this coupling reaction. Several arylboronates containing electron-donating (NMe(2), OMe, and Me) and -withdrawing (CF(3) and F) groups were also applicable to this coupling reaction. Intermolecular competitive reaction using pivalophenone-d(0)() and -d(5) and intramolecular competitive reaction using pivalophenone-d(1) were carried out using 3 as a catalyst. The k(H)/k(D) value for the intermolecular competitive reaction was substantially different, compared with intramolecular competitive reaction. This strongly suggests the production of an intermediate where the ketone carbonyl is coordinated to the ruthenium involved in this catalytic reaction. (1)H and (11)B NMR studies using 2'-methylacetophenone, phenylboronate (2), and pinacolone (6) indicate that 6 functions effectively as a scavenger of the HB species.     

Simple and efficient nickel-catalyzed cross-coupling reaction of alkynylalanes with benzylic and aryl bromides

Highly efficient and simple coupling reactions of benzylic and aryl bromides with aluminium acetylide catalyzed by NiCl(2)(PPh(3))(2) are reported. The coupling reactions proceed at room temperature employing 4 mol% catalyst, affording coupling products in excellent yields of up to 95% in short reaction times. The system worked efficiently with aryl and heterocyclic bromides as well.     

Palladium charcoal-catalyzed Suzuki-Miyaura coupling to obtain arylpyridines and arylquinolines

A phosphine ligand, such as PPh3 or 2-(dicyclohexylphosphino)biphenyl, is essential for the Pd/C-catalyzed Suzuki-Miyaura coupling of halopyridines and haloquinolines, although it has been reported that the reaction of phenyl chlorides can be catalyzed by nonprereduced Pd/C without any additives. In the reactions of bromopyridines, bromoquinolines, 2-chloropyridines, and 2-chloroquinolines, PPh3 was effective enough to provide coupling products in good yields. However, in the reactions of 3-chloropyridine, 4-chloropyridine, and 6-chloroquinoline, sterically hindered 2-(dicyclohexylphosphino)biphenyl was indispensable as a ligand.     

An efficient nickel-catalyzed alkenylation of functionalized benzylic halides with alkenylaluminum reagents

Highly efficient and simple coupling reactions of benzylic bromides or chlorides with alkenylaluminum reagents catalyzed by NiCl(2)(PPh(3))(2) are reported. The coupling reactions proceed effectively at room temperature employing low loading of catalyst, 0.5 mol% for benzylic bromides having either electron-donating or -withdrawing substituents on the aromatic ring, affording coupling products in excellent yields of up to 94% in short reaction times. The coupling reactions of benzylic chloride require 5 mol% of the catalyst and a longer reaction time of 2 h.     

Catalytic addition of C-H bonds to multiple bonds with the aid of ruthenium complexes

Ruthenium complexes, e.g., RuH2(CO)(PPh3)3, have been found to catalyze the direct addition of ortho carbon-hydrogen bonds of aromatic ketones to olefins and acetylenes with high efficiency and selectivity. The C-H/olefin coupling reaction is applicable to not only C-H bonds in aromatic ketones but also to those in a,b-enones and aro-matic esters. Catalytic addition of ortho carbon-hydrogen bonds of aromatic imines to olefins is found to be catalyzed by Ru3(CO)12.     

Room-temperature regioselective C-H/olefin coupling of aromatic ketones using an activated ruthenium catalyst with a carbonyl ligand and structural elucidation of key intermediates

Mechanistic studies of the ruthenium-catalyzed reaction of aromatic ketones with olefins are presented. Treatment of the original catalyst, RuH(2)(CO)(PPh(3))(3), with trimethylvinylsilane at 90 °C for 1-1.5 h afforded an activated ruthenium catalyst, Ru(o-C(6)H(4)PPh(2))(H)(CO)(PPh(3))(2), as a mixture of four geometric isomers. The activated complex showed high catalytic activity for C-H/olefin coupling, and the reaction of 2'-methylacetophenone with trimethylvinylsilane at room temperature for 48 h gave the corresponding ortho-alkylation product in 99% isolated yield. The activated catalyst was thermally robust and showed excellent catalytic activity under refluxing toluene conditions. (1)H and (31)P NMR studies of the C-H/olefin coupling at room temperature suggested that an ortho-ruthenated complex, P,P'-cis-C,H-cis-Ru(2'-(6'-MeC(6)H(4)C(O)Me))(H)(CO)(PPh(3))(2), participated in the reaction as a key intermediate. Isotope labeling studies using acetophenone-d(5) indicated that the rate-limiting step was the C-C bond formation, not the C-H bond cleavage, and that each step prior to the reductive elimination was reversible. The rate of C-H/olefin coupling was found to exhibit pseudo first-order kinetics and to show first-order dependence on the ruthenium complex concentration.     

Rhodium-catalyzed novel trifluoromethylation at the alpha-position of alpha,beta-unsaturated ketones

Treatment of alpha,beta-unsaturated ketones with CF(3)I in the presence of Et(2)Zn and RhCl(PPh(3))(3) gave novel alpha-trifluoromethylation products in good yields. Hydrogen transfer from the ethyl group on the rhodium complex to the beta-position of the enone seems to play an important role in this reaction.     

Direct synthesis of 1,3-diketones by Rh-catalyzed reductive alpha-acylation of enones

1,3-Diketones were synthesized from alpha,beta-unsaturated ketones by treatment with acid chlorides and Et(2)Zn in the presence of RhCl(PPh(3))3. This is a very simple and extremely chemoselective reaction to give the adduct at the alpha-position of alpha,beta-unsaturated ketones.     

Osmium pyme complexes for fast hydrogenation and asymmetric transfer hydrogenation of ketones

The osmium compound trans,cis-[OsCl2(PPh3)2(Pyme)] (1) (Pyme=1-(pyridin-2-yl)methanamine), obtained from [OsCl2(PPh3)3] and Pyme, thermally isomerizes to cis,cis-[OsCl2(PPh3)(2)(Pyme)] (2) in mesitylene at 150 degrees C. Reaction of [OsCl2(PPh3)3] with Ph2P(CH2)(4)PPh2 (dppb) and Pyme in mesitylene (150 degrees C, 4 h) leads to a mixture of trans-[OsCl2(dppb)(Pyme)] (3) and cis-[OsCl2(dppb)(Pyme)] (4) in about an 1:3 molar ratio. The complex trans-[OsCl2(dppb)(Pyet)] (5) (Pyet=2-(pyridin-2-yl)ethanamine) is formed by reaction of [OsCl2(PPh3)3] with dppb and Pyet in toluene at reflux. Compounds 1, 2, 5 and the mixture of isomers 3/4 efficiently catalyze the transfer hydrogenation (TH) of different ketones in refluxing 2-propanol and in the presence of NaOiPr (2.0 mol %). Interestingly, 3/4 has been proven to reduce different ketones (even bulky) by means of TH with a remarkably high turnover frequency (TOF up to 5.7 x 10(5) h(-1)) and at very low loading (0.05-0.001 mol %). The system 3/4 also efficiently catalyzes the hydrogenation of many ketones (H2, 5.0 atm) in ethanol with KOtBu (2.0 mol %) at 70 degrees C (TOF up to 1.5 x 10(4) h(-1)). The in-situ-generated catalysts prepared by the reaction of [OsCl2(PPh3)3] with Josiphos diphosphanes and (+/-)-1-alkyl-substituted Pyme ligands, promote the enantioselective TH of different ketones with 91-96 % ee (ee=enantiomeric excess) and with a TOF of up to 1.9 x 10(4) h(-1) at 60 degrees C.     

Efficient synthesis of 2,2-diaryl-1,1-difluoroethenes via consecutive cross-coupling reactions of 2,2-difluoro-1-tributylstannylethenyl p-toluenesulfonate

2,2-Difluoro-1-tributylstannylethenyl p-toluenesulfonate (2) was reacted with aryl iodides in the presence of 10 mol % of Pd(PPh(3))(4) and 10 mol % of CuI in DMF at 80 °C for 10-20 h to give the cross-coupled products 3 in 35-97% yields. Further coupling reaction of 3 with arylstannanes in the presence of 5 mol % of Pd(PPh(3))(4) and 3 equiv of LiBr in DMF at 100 °C for 2-24 h afforded the desired products 5 in 25-78% yields.     

Anti-selective and regioselective aldol addition of ketones with aldehydes using MgI2 as promoter

The first example of a direct aldehyde-ketone coupling using the secondary amine piperidine as base in the presence of MgI₂ to generate high selectivity of anti-aldol products from unmodified ethyl ketones in high yield is reported. The coupling reactions were carried out in a one-pot reaction by mixing four reaction components at room temperature. In the case of unsymmetrical ketones, addition was made to the less hindered α-side.     

Nickel-catalyzed cross-coupling reaction of grignard reagents with alkyl halides and tosylates: remarkable effect of 1,3-butadienes

A new method for the cross-coupling reaction of Grignard reagents with alkyl chlorides, bromides, and tosylates has been developed by the use of a nickel catalyst in the presence of a diene as an additive. This reaction proceeds efficiently at 0-25 degrees C in THF using primary and secondary alkyl and aryl Grignard reagents. Nickel complexes bearing no phosphine ligands, such as NiCl2, Ni(acac)2, and Ni(COD)2, afford the coupling products in good yields, whereas NiCl2(PPh3)2 and NiCl2(dppp) were less effective. 1,3-Butadiene shows the highest activity as an additive for the present coupling reaction. A plausible reaction pathway was proposed.     

Gold-catalyzed hydrative carbocyclization of 1,5- and 1,6-diyn-3-ones via an oxygen transfer process

This study reports new hydrative carbocyclizations of 1,5- and 1,6-diyn-3-ones catalyzed by PPh3AuOTf, involving a pi-alkyne-assisted oxygen transfer in the reaction mechanisms. Treatment of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes with PPh3AuOTf (5 mol %) in wet 1,4-dioxane (23 degrees C, 10 min) led to hydrative aromatization to give 4-hydroxyl-1-naphthyl ketones efficiently. This approach is also extendible to the hydrative cyclization of acyclic 1,5-diyn-3-ones, which afforded 4-cyclopentenonyl ketones in reasonable yields. On the basis of this oxygen-labeling study, we propose a plausible mechanism involving an alkyne-assisted oxygen transfer to generate key oxonium and gold-enolate intermediates.     

Ortho alkylation of aromatic ketimine with functionalized alkene by Rh(I) catalyst

[reaction: see text] The reaction of the imine of aromatic ketones with functionalized alkenes was performed under a catalytic amount of (PPh3)3RhCl, and corresponding ortho-alkylated ketones were obtained after hydrolysis. A variety of functional groups in the alkene were tolerated in this ortho alkylation. This procedure expands the scope of ortho alkylation to the direct ortho functionalization of aromatic ketones.     

An efficient direct alpha-alkylation of ketones with primary alcohols catalyzed by [Ir(cod)Cl]2/PPh3/KOH system without solvent

alpha-Alkylation of ketones was successfully achieved by the reaction of ketones with alcohols catalyzed by iridium complexes in the presence of a small amount of base. For example, 2-octanone was allowed to react with butanol under the influence of [Ir(cod)Cl]2/PPh3/KOH to give 6-dodecanone in good yield. The reaction was found to proceed by using a 1:1 mixture of ketone and alcohol without use of any solvent.     

一种侧基横挂偶极单元的聚苯撑乙炔的光学性质

以对苯二乙炔和2,5-二溴苯衍生物为单体,无水N,N-二甲基甲酰胺（DMF）为溶剂,通过Sonogashira偶联反应,采用2种Pd催化剂（Pd(PPh₃)₄和PdCl₂(PPh₃)₂）合成了一种侧基带有偶极基团的聚苯撑乙炔。 单体的化学结构通过IR、NMR和元素分析等测试技术得到确证。 聚合物外观为黄色粉状固体,室温下溶于CHCl₃和THF等有机溶剂。 2种Pd催化剂对合成聚合物的分子量以及光学性质影响不大,但对聚合物的发光效率影响较大,由Pd(PPh₃)₄催化得到的聚合物分子链具有较高的立构规整性,因此,具有较高的发光效率。 不同溶剂环境以及聚合物固体膜的紫外以及荧光光谱研究结果表明,侧基偶极基团的相互静电排斥力,可以有效阻止大分子链之间的聚集,从而有效地抑制了聚苯撑乙炔聚集体的形成。     

Palladium(0)-catalyzed amination,Stille coupling,and Suzuki coupling of electron-deficient aryl fluorides

The amination of 2-fluoronitrobenzene was Pd(0) catalyzed at 65 degrees C in DMF, and the effectiveness of the catalysis was ligand-dependent. Among the five catalyst systems investigated, Pd(PPh3)4 was the most effective catalyst. The control experiments revealed that Pd(OAc)2 or PPh3 was not responsible for the catalysis. 4-Fluoro-3-nitro-benzonitrile and 4-fluoro-3-nitro-benzaldehyde also underwent Stille coupling and Suzuki coupling in the presence of Pd(PPh3)4, and the reactions afforded the coupling products in 28-86% yields. The control experiments showed no sign of reaction in the absence of palladium. These results were in agreement with the oxidative addition/reductive elimination pathway, where the oxidative addition could conceivably proceed via the SNAr mechanism.     

镍络合物催化条件下2,2'-联吡啶的偶联合成

在制备联吡啶的偶联反应中，镍化合物和三苯基膦通常是以化学计量参与反应 。我们在对Tiecco报道的偶联反应进行研究的过程中发现，这一反应可以在催化条 件下进行。这一改进订基于投料顺序的改变，充分利用零价镍当场（in situ）生 成时的高活性。将氯化镍、三苯基膦、2-溴吡啶先溶于DMF中，然后在50 ℃时加入 锌粉，催化偶联生成联吡啶，可以获得满意的收率。同时对三种镍化合物的反应活 性作了比较，以NiCl_2·6H_2O活性最高。