Single-flask preparation of polyazatriaryl ligands by sequential borylation/Suzuki-Miyaura coupling

We report a convenient single-flask methodology for the preparation of polyazatriaryl products with relevance to luminescence, catalysis, and pharmacology. The diborylation of 1,3-dibromobenzenes and double Suzuki-Miyaura coupling produces 1,3-diheteroarylbenzenes. Similarly, borylation of heteroaryl halides and double coupling to 2,6-dichloropyridine produces 2,6-diheteroarylpyridines. This methodology appears general in producing challenging polyheteroaryl targets as long as the boronic esters have no ortho heteroatoms and coupling avoids adjacent oxygens.     

Synthesis of new di-anchoring organic sensitizer based on quinoxaline acceptor for dye-sensitized solar cells

New quinoxaline-based organic sensitizer bearing di-anchoring group for dye-sensitized solar cells (DSSCs) was synthesized from diethyl 4,5-diaminophthaltate, in which was prepared under mild condition by using Takehito’s method. The synthesized sensitizer was compared with mono-anchoring sensitizer through absorption spectra, emission spectra, J-V curve, and IPCE spectra, indicating the di-anchoring group leads to a noticeable improvement of J_sc value owing to more efficient intramolecular charge transfer and channel number increment.     

Suzuki-Miyaura coupling for general synthesis of dehydrocoelenterazine applicable for 6-position analogs directing toward bioluminescence studies

Synthesis of coelenterazine analogs is in recent demand to supply more luminescent compounds with reasonable stability as substrate for the photoprotein manipulated in a living cells or particular organelle. There are limited methods for the synthesis of 6-substituted coelenterazine due to the route and instability of the compounds under the existing conditions. This paper describes six examples including Suzuki-Miyaura cross coupling reaction with reactive triflate (unstable) and stable tosylate intermediates of the imidazo[1,2-a]pyrazin-3-one. Five examples of 2-amino-3-benzyl-5-O-Tf-pyrazine are also discussed. The product coelenterazine analogs are obtained in the form of dehydrocoelenterazine, which is the substrate of a squid photoprotein, symplectin.     

Suzuki-Miyaura coupling in the presence of (2,2,2-triferrocenylethyl)diphenylphosphane

The electron rich and sterically bulky title phosphane was prepared and efficiently applied in the palladium catalyzed Suzuki-Miyaura cross-coupling reaction. With electron rich aryl chlorides and bromides the yields and reaction times were significantly improved by microwave heating.     

Expanding the scope of the Cu assisted Suzuki-Miyaura reaction

Recent advances in the development of the copper facilitated Suzuki-Miyaura reaction are described. Improvements include expansion of substrate scope to include aryl chlorides and polyhalo aryl boronates. It was found that use of S-Phos and X-Phos could accomplish the coupling of 2-pyridyl boronates to aryl chlorides and bromides in shorter reaction times and in higher yield than previously described with DPPF.     

Ni(PPh3)2Cl2催化2-氯嘧啶与芳基硼酸的Suzuki-Miyaura偶联反应

本文在Ni(PPh3)2 Cl2催化下顺利实现了不同取代基2-氯嘧啶与芳基硼酸的Suzuki-Miyaura偶联反应.实验表明,取代基的电子效应和空间位阻效应对2-氯嘧啶的反应活性影响较小.该反应产率良好,官能团耐受性好,为2-芳基嘧啶衍生物的合成提供了一类简单有效的方法.     

An expeditious aqueous Suzuki-Miyaura method for the arylation of bromophenols

The development of a novel Suzuki-Miyaura method has been achieved to allow the efficient arylation of bromophenols. A range of functionality is tolerated with regard to the boronic acid coupling partner and the reaction exhibits complete chemoselectivity for the C_aryl-Br bond versus the C_aryl-Cl bond in the aryl halide input. The experimental protocol features a short reaction time of 15 min, utilizes inexpensive Pd/C as a catalyst, and is conducted with water as the solvent.     

An efficient and general synthesis of 3-substituted propionaldehydes using the Suzuki-Miyaura coupling

An efficient method to prepare 3-substituted propionaldehyde derivatives using a Suzuki-Miyaura coupling is reported. The reaction has been demonstrated on a range of substrates including several where the Heck reaction with allyl alcohol failed to give the desired aldehyde product.     

Suzuki coupling reaction for the solid-phase preparation of 5-substituted nicotinic acid derivatives

The application of the Suzuki coupling reaction to the preparation of small combinatorial libraries using 5-bromonicotinic acid as a scaffold onto three different types of solid support (Wang, Rink, and BAL resin) is described.     

An efficient Pd(II)-(2-aminonicotinaldehyde) complex as complementary catalyst for the Suzuki-Miyaura coupling in water

An efficient new Pd(II)-(2-aminonicotinaldehyde)-catalyzed Suzuki-Miyaura coupling of the aryl halides (Br, Cl and I) and organoboronic acids at moderate temperature in water is described. Low catalyst loading, easy accessibility, being an air-stable catalyst, functional group compatibility, and water as the reaction medium are some of the key features of this synthetic method. This protocol is also applicable for gram scale.     

One-pot synthesis of 1,4-diarylsubstituted 1,3-diynes from the sequential coupling reactions of aryl iodides and propiolic acid

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.     

Synthesis and cross coupling of a highly substituted 2-pyridylboronate: application to the large scale synthesis of a mineralocorticoid antagonist

The large scale synthesis of functionalized 2-pyridylboronate 8 and optimization of its Suzuki-Miyaura coupling to chloropyrazoline (R)-7 to provide a scalable synthesis of mineralocorticoid antagonist (R)-1 is described.     

Use of thiopropyl sepharose for preparation of 2-nitro-5-thiobenzoic acid

A simple method is described for preparation of 2-nitro-5-thiobenzoic acid (NTB), a compound with versatile applications but is commercially unavailable. In this method, NTB is produced by the reduction of 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) with thiopropyl sepharose, which is then separated from NTB by filtration. Two molecules of NTB can be generated from each molecule of DTNB when a large excess of thiopropyl sepharose is used. Thiopropyl sepharose is commercially available and can be readily regenerated for repeated use in the preparation of NTB. This method is simple and more effective than any other reported methods of NTB preparation.     

A general and efficient synthesis of substituted fluorenes and heterocycle-fused indenes containing thiophene or indole rings utilizing a Suzuki-Miyaura coupling and acid-catalyzed Friedel-Crafts reactions as key steps

A general and efficient synthesis of fluorenes or heterocycle-fused indenes including 3-thia-cyclopenta[a]indenes, 9-thia-indeno[1,2-a]indenes, 5,6-dihydroindeno[2,1-b]indoles has been developed. This methodology is realized by a multistep protocol involving first preparation of ortho-formylbiaryls through Suzuki-Miyaura coupling of o-bromobenzaldehydes with arylboronic acids or the coupling of aryl halides with 2-formylbenzene boronic acid, this is followed by Grignard addition and Friedel-Crafts cyclization reactions catalyzed by Brønsted or Lewis acid to form the desired fluorene or indene rings. The method offers several advantages such as high yields, high selectivities, mild reaction conditions, easily accessible starting materials, and so on.     

A direct route for the preparation of Fmoc/OtBu protected iodotyrosine

Herein the synthesis of an Fmoc/O^tBu orthogonally protected iodotyrosine derivative is reported. This has been achieved via a simple two-step process in an overall 58% yield from commercially available Fmoc-Tyr(^tBu)-OH. The Fmoc/O^tBu orthogonally protected iodotyrosine was also shown to be amenable to Suzuki-Miyaura cross-coupling to deliver a novel bi-aryl tyrosine derivative.     

An improved Ullmann-Ukita-Buchwald-Li conditions for CuI-catalyzed coupling reaction of 2-pyridones with aryl halides

An effective CuI-trans-N,N′-dimethylcyclohexane-1,2-diamine (DMCDA)-K₂CO₃-catalyzed coupling reaction of 2-pyridones with aryl halides is described. Under our conditions, DMCDA was found to be an effective catalyst that facilitates the coupling reactions even in toluene, a common industrial solvent. In addition, 3-bromopyridine could also be coupled effectively under these conditions, indicating that the catalytic reactivity of this system is high. The reaction could be applied for polymer modification and iterative oligo-pyridone synthesis.     

A highly efficient and recyclable NiCl2(dppp)/PEG-400 system for Suzuki-Miyaura reaction of aryl chlorides with arylboronic acids

Abstract

NiCl₂(dppp) in PEG-400 is shown to be a highly efficient catalyst for Suzuki-Miyaura coupling of aryl chlorides with arylboronic acids. The reaction could be conducted at 100?°C using K₃PO₄ as base, yielding a variety of biaryls in good to excellent yields. The isolation of the products was readily performed by extraction with petroleum ether and NiCl₂(dppp)/PEG-400 system could be easily recycled and reused up to five times without significant loss of activity. Our system not only avoids the use of easily volatile and toxic dioxane or toluene as a solvent but also solves the basic problem of nickel catalyst reuse.     

碱性条件下Ru/C催化5-羟甲基糠醛选择氧化反应

以活性炭负载金属钌(Ru/C)为催化剂,在碱性水溶液中研究了5-羟甲基糠醛(HMF)选择氧化反应.与MgO,Ca(OH)₂和NaOH相比,加入具有合适碱强度的镁铝水滑石有利于生成5-甲酰基-2-呋喃甲酸(FFCA)或2,5-呋喃二甲酸(FDCA).X射线光电子能谱实验表明金属态的钌是活性催化中心.同位素示踪结果则表明水而非氧气提供了5-甲酰基-2-呋喃甲酸及2,5-呋喃二甲酸等羧酸产物的氧源.根据这些结果,并结合HMF和2,5-呋喃二甲醛氧化的动力学研究,我们提出HMF选择性氧化制备FFCA遵循Langmuir-Hinshelwood反应机理.其中,HMF在金属Ru表面饱和解离吸附,在解离吸附的氧原子的协助下发生β-脱氢生成2,5-呋喃二甲醛(DFF)吸附物种.该DFF物种进一步发生水合与氧化形成FFCA产物.     

Use of Pd-catalyzed Suzuki-Miyaura coupling reaction in the rapid synthesis of 5-aryl-6-(phosphonomethoxy)uracils and evaluation of their inhibitory effect towards human thymidine phosphorylase

A number of new 5-aryl substituted pyrimidine acyclic nucleoside phosphonates were synthesized and tested for their ability to inhibit human TP. Their rapid synthesis using Pd-catalyzed Suzuki-Miyaura coupling reactions of various arylboronic acids with 5-bromo-4-(phosphonomethoxy)-2,6-dibutoxypyrimidine was successfully applied. For a series of 5-aryl-6-phosphonomethoxyuracils, an increased inhibitory effect was determined. This effect is supported by the results found for 4-fluorophenyl (K_i^dThd=4.89±0.62) and 3-nitrophenyl (K_i^dThd=3.98±0.46) substituents.