Selective double Suzuki cross-coupling reactions. Synthesis of unsymmetrical diaryl (or heteroaryl) methanes

Using a double Suzuki cross-coupling reaction ortho- or para-bromobenzyl bromides are easily transformed into unsymmetrical diaryl (or heteroaryl) methanes     

Photochromic Dihetarylethenes. 8. A Novel Route to the Synthesis of 3,4-Bis(2,5-dimethyl-3-thienyl)furan-2,5-dione as a Potential Photochrome

There is proposed, and in the case of 2,5-dimethylthiophene carried out, a novel route to the synthesis of 3,4-dithienylfuran-2,5-dione type photochromes. This is done in two stages, the first being a Friedel-Crafts reaction of the starting thiophene with the dichloride of squaric acid and the second is a Baeyer-Villiger oxidation of the 3,4-bis(2,5-dimethyl-3-thienyl)cyclobutenedione to give the target 3,4-bis(2,5-dimethyl-3-thienyl)furan-2,5-dione.     

The Discovery of a Palladium(II)‐Initiated Borono‐Catellani Reaction

Reported is a novel palladium(II)‐initiated Catellani‐type reaction that utilizes widely accessible aryl boronic acids as the substrates instead of aryl halides, thereby greatly expanding the existing scope of this powerful transformation. This borono‐Catellani reaction was promoted by cooperative catalysis between Pd(OAc)₂ and the inexpensive 5‐norbornene‐2‐carbonitrile. Practicality is the striking feature of the reaction: it is run open to air at ambient temperature and no phosphine ligand is needed. This mild, chemoselective, and scalable protocol is compatible with a large range of readily available functionalized aryl boronic acids and bromides, as well as terminating olefins (50 examples, 39–97 % yields). Moreover, the orthogonal reactivity between the borono‐Catellani and classical Catellani reaction was demonstrated. This work is expected to open new avenues for developing novel Catellani‐type reactions.     

Synthesis and photochromic properties of tetrakis(3,5-dimethyl-2-thienyl)- and tetrakis(2,5-dimethyl-3-thienyl)ethylenes

Tetrakis(3,5-dimethyl-2-thienyl)ethylene and tetrakis(2,5-dimethyl-3-thienyl)ethylene were obtained from the corresponding dithienyl ketones by the McMurry reaction. The photochromic properties of the compounds obtained were studied. Dedicated to the Academician N. K. Kochetkov on the occasion of his 90th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1177–1181, May, 2005.     

Palladium‐Catalyzed Synthesis of (Hetero)Aryl Alkyl Sulfones from (Hetero)Aryl Boronic Acids,Unactivated Alkyl Halides,and Potassium Metabisulfite

A palladium‐catalyzed one‐step synthesis of (hetero)aryl alkyl sulfones from (hetero)arylboronic acids, potassium metabisulfite, and unactivated or activated alkylhalides is described. This transformation is of broad scope, occurs under mild conditions, and employs readily available reactants. A stoichiometric experiment has led to the isolation of a catalytically active dimeric palladium sulfinate complex, which was characterized by X‐ray diffraction analysis.     

Enantioselective Synthesis of Chromenes via a Palladium‐Catalyzed Asymmetric Redox‐Relay Heck Reaction

A palladium‐catalyzed asymmetric redox‐relay Heck reaction of 4H ‐chromenes and arylboronic acids has been successfully developed. The reaction proceeded in moderate to good yields with good to high enantioselectivities. The resulting product is an advanced intermediate of bio‐active compound BW683C.     

α-二亚胺钯配合物的合成及催化Suzuki偶联反应

设计合成并表征了3个具有不同骨架结构的α-二亚胺钯配合物,并在有氧条件下催化不同溴代芳烃与芳硼酸的Suzuki偶联反应,重点考察了配合物骨架结构、碱性强度、溶剂极性和不同反应温度对催化反应的影响。结果表明,α-二亚胺类钯配合物能催化Suzuki偶联反应,采用质子溶剂、无机碱,以及较高反应温度都有利于偶联反应的进行,能够高效制备一系列联芳类化合物。     

Synthesis and Crystal Structure of 2,5—Bis（morpholino）—3,4—bis（p—chlorophenyl）thiophene

1 INTRODUCTION -Thiocarbonylthioformamide synthesized in 1980[1, 2] is a class of stable and almost unexplored compounds[3]. We have reported the reaction of - thiocarbonylthioformamides in our previous paper[4]. Here, we will report a novel synthesis of 2 by the reaction of 1 and trimethyl phosphite in refluxing xylene. In order to determine the structure of 2, X- ray crystallographic study was carried out. 2 EXPERIMENTAL 2. 1 Preparation of the title compound Trimethyl phosph…     

Chemoselective Synthesis of Polysubstituted Pyridines from Heteroaryl Fluorosulfates

A selection of heteroaryl fluorosulfates were readily synthesized using commercial SO₂F₂ gas. These substrates are highly efficient coupling partners in the Suzuki reaction. Through judicious selection of Pd catalysts the fluorosulfate functionality is differentiated from bromide and chloride; the order of reactivity being: ‐Br> ‐OSO₂F> ‐Cl. Exploiting this trend allowed the stepwise chemoselective synthesis of a number of polysubstituted pyridines, including the drug Etoricoxib.     

Synthesis of 2,5 -Bis(4-methyl-2-thienyl)thiophene and 2,5-Bis(4-methyl-2-thienyl)pyrrole

Syntheses of 2,5-bis(4-methyl-2-thienyl)thiophene 3 and 2,5-bis(4-methyl-2-thienyl)pyrrole 4 are described. The key step involves Stetter reaction between 4-methyl-2-thiophenecarboxaldehyde and divinyl sulfone. Cyclizaton of the resulting 1,4-bis-(4-methyl-2-thienyl)-1,4-butanedione 2 with Lawesson's reagent gives 2,5-bis(4-methyl-2-thienyl)thiophene 3, whereas condensation with ammonium acetate provides the 2,5-bis(4-methyl-2-thienyl)pyrrole 4.     

Convenient Preparation of Cycloalkenyl Boronic Acid Pinacol Esters

A practical method for the preparation of cycloalkenyl boronic acid pinacol esters is described. These important synthetic intermediates are typically made using more expensive methods like transition metal-catalyzed borylation of alkenyl halides or triflates. In this work, they are obtained from the simple corresponding cycloalkanones, which are subjected to Shapiro reaction conditions followed by trapping with a borate ester. The requisite products are obtained in very good to excellent yields, and the reactions can be scaled up to multigram amounts. By providing a simple alternative to common methods that make use of expensive transition-metal catalysts and formation of sensitive intermediates, this convenient method will be useful for the synthesis of ring-containing partners for Suzuki–Miyaura cross-coupling and other reactions employing boronic esters as substrates.     

Synthesis and reduction of 5,5-dimethyl-2,4-bis(3,4-dimethoxyphenyl)-2-chloro-2,5-dihydrofuran

A new, stable 5-membered ring heterocyclic cation was prepared and reduced into the corresponding dihydrofuran, tetrahydrofuran and pentanol derivatives.     

Synthesis of novel 2,5-bis(5-aryl-1,3,4-oxadiazol-2-yl)furans from furan-2,5-dicarboxylic acid dihydrazide and trichloromethylarenes

2,5-Bis(5-aryl-1,3,4-oxadiazol-2-yl)furans are synthesized via the reaction of trichloromethylarenes with furan-2,5-dicarboxylic acid dihydrazide. The structures of the products are confirmed by IR and mass spectra.N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences, Moscow 117913, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 993–996, July, 1999.     

Synthesis of Substituted 1,2,4-Triazines Based on 1,2-Bis(2,5-dimethyl-3-thienyl)ethanedione

A novel, convenient method has been developed for the synthesis of 1,2-bis(2,5-dimethyl-3-thienyl)ethanedione, from which were prepared 5,6-bis(2,5-dimethyl-3-thienyl)-1,2,4-triazines (analogs of the photochromic 1,2-diarylethenes). The principial possibility of using 1,2,4-triazines obtained as photochromic agents was investigated.     

Synthesis and application of ortho-palladated complex of (4-phenylbenzoylmethylene)triphenylphosphorane as a highly active catalyst in the Suzuki cross-coupling reaction

The ortho-metallated complex [Pd(μ-Cl){κ₂(C,C)-[C₆H₄(PPh₂CHC(O)C₆H₄-Ph-4)}]₂ (2a) was prepared by refluxing of Pd(OAc)₂ and {(Ph)₃PCHCOC₆H₄-Ph-4} (PhBPPY) of in CH₂Cl₂ followed by addition of an excess of KCl in MeOH Complex (2a) reacts with triphenylphosphine to give the mononuclear derivative [Pd(Cl)(PhC₆H₄COCHPPh₂C₆H₄)(PPh₃)] (3a) whose crystal structure has been determined by single crystal X-ray diffraction. The Suzuki reactions of aryl bromides and chlorides of varying electron density using complex (3a) as an efficient catalyst were performed, giving the cross-coupling products in good to excellent yields.     

2,5-Bis-(butyltelluro) thiophene as a convenient precursor for the synthesis of 2,5-bis-(acetylenic) thiophenes

Both symmetrically and unsymmetrically substituted 2,5-bis-(acetylenic) thiophene derivatives were obtained in good yields under mild conditions through palladium-catalyzed cross coupling reaction of 2,5-bis-(butyltelluro) thiophene 2 and terminal alkynes. The methodology represents a general and efficient protocol for carrying out the synthesis of thiophene derivatives with potential biological activities.     

Nickel and Copper Catalyzed ipso-Phosphonodifluoromethylation of Arylboronic Acids with BrCF2P(O)(OEt)2 for the Synthesis of Phosphonodifluoromethylarenes

A convenient method for the direct ipso-phosphonodifluoromethylation of arylboronic acids via nickel-copper co-catalysis is disclosed. This work, which utilizes inexpensive first row transition metals, represents a facile alternative to the traditional palladium catalyzed approach. The method utilizes inexpensive commodity chemicals and substrates while tolerating a variety of biologically relevant functional groups. Structurally diverse phosphonodifluoromethylarenes are furnished in good yields under short reaction times. Control experiments to probe possible reaction pathways are also included.     

One-pot synthesis of substituted styrenes from vicinal dibromoalkanes and arylboronic acids

Dehydrobromination of vicinal dibromoalkanes in systems comprising 1,2-dimethoxy-ethane, N-butyl-N′-methylimidazolium tetrafluoroborate (or tetrabutylammonium bromide), and a base with subsequent palladium-catalyzed cross-coupling of the thus formed bromoalkenes with arylboronic acids furnished substituted styrenes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 116–123, January, 2007.     

One-Pot Synthesis of 2,3-Diarylbenzofurans via Sequential Iodocyclization and Pd-Catalyzed Suzuki Coupling Reactions of 2-Alkynylanisoles with Boronic Acids in Water

An efficient approach for the one-pot synthesis of 2,3-diarylbenzofurans via sequential iodocyclization and Pd-catalyzed Suzuki coupling reaction of 2-alkynylanisoles with boronic acids in water is reported. The protocol utilizes water as the solvent and there is no need to isolate the intermediate 3-iodine-2-arylbenzofurans, which exemplifies the ideal of green chemistry. Various 2-alkynylanisoles and boronic acids can participate in the reactions, providing a series of 2,3-diarylbenzofurans for drug discovery in moderate to good yields.