Displacement reactions of 2-chloro- and 2,9-dichloro-1,10-phenanthroline: synthesis of a sulfur-bridged bis-1,10-phenanthroline macrocycle and a 2,2′-amino-substituted-bis-1,10-phenanthroline

The synthesis and structural assignments of 9-chloro-1,1-phenanthroline-2(1H)-thione and 1,10-dihydro-1,10-phenanthroline-2,9-dithione have been accomplished. The sulfur-bridged bis-1,10-phenanthroline macrocycle was readily prepared by heating the thione or equimolar amounts of the dithione and 2,9-dichloro-1,10-phenanthroline in diphenyl ether. Displacements of 2-chloro- or 2,9-dichloro-1,10-phenanthroline with N,N-dimethylethylenediamine afforded the corresponding amine and diamino analogues. An amino-substituted-2,2′-bis-1,10-phenanthroline has been prepared.     

Copper(I)-2-(2′-pyridyl)benzimidazole catalyzed N-arylation of indoles

CuI-2-(2′-pyridyl)benzimidazole catalyst system can serve efficiently to promote N-arylation of various indoles to afford the N-arylated indoles. The bidentate ligand, 2-(2′-pyridyl)benzimidazole was proved superior to monodentate nitrogen-based ligands and well-known bidentate ligands such as 2,2′-bipyridyl and 1,10-phenanthroline.     

Synthesis and reactions of 1,10-phenanthroline-2(1H)-thione: a facile synthesis of 2,2′-thiobis-1,10-phenanthroline

Treatment of 2-chloro-1,10-phenanthroline with NaSH hydrate in DMF, Na₂S nonahydrate in DMF or thiourea in refluxing ethanol readily afforded 1,10-phenanthroline-2(1H)-thione. This thione undergoes reaction with 1,2-dibromoethane to yield a thiazole bromide salt. Upon heating the thione in diphenyl ether with 2-chloro-1,10-phenanthroline, the hydrochloride salt of 2,2′-thiobis-1,10-phenanthroline precipitated and could be converted into the corresponding free base on treatment with aqueous base. Heteroaryl substituted sulfides could be prepared by treatment of 2-chloro-1,10-phenanthroline with pyridine-2-thione or pyrimidine-1-thione with potassium carbonate in DMF.     

Ring opening reactions of pyromellitic dianhydride for the synthesis of first row transition metal dicarboxylate complexes

The ring opening reaction of pyromellitic dianhydride by methanol is an effective method to prepare first row transition metal dicarboxylate complexes. The reactions of different first row transition metal salts with pyromellitic dianhydride in the presence of nitrogen donating bidentate ligands such as 1,10-phenanthroline and 2,2′-bipyridine gives different compositions depending on the ligand and the metal salts used. For example, the reaction of nickel(II) acetate with pyromellitic dianhydride in the presence of 1,10-phenanthroline results in the formation of a carboxylato bridged nickel(II) metallacycle through the ring opening reaction of pyromellitic dianhydride (PAH) at the 1 and 3-positions, whereas a mononuclear tetra-aqua 2,2′-bipyridine nickel(II) complex is formed in a similar reaction of nickel(II) acetate through ring opening at the 1,4-position of PAH. Mononuclear cobalt(II) dicarboxylate complexes are formed from the ring opening reaction of pyromellitic dianhydride in methanol in the presence of the nitrogen donor ligands 1,10-phenanthroline or 2,2′-bipyridine. Copper(II) chloride on reaction with PAH and 2,2′-bipyridine gives a mononuclear complex via ring opening at the 1 and 4-positions; having chlorides inside and outside the coordination sphere. Whereas, the reaction of copper(II)acetate gives dinuclear copper complexes having a monodentate carboxylato bridge arising from the carboxylato groups at the 1 and 4-positions on the aromatic ring. The crystal structures of all the complexes have been determined.     

Synthesis of unnatural 3′-phospha-2′-deoxyfuranose nucleoside analogues

This Letter describes the synthesis of racemic analogues of unnatural 2′-deoxy nucleoside with a phosphorus atom replacing the carbon atom in the 3′-position. A seven-step sequence was developed in racemic series to afford unnatural 3′-phospha-2′-deoxyfuranose nucleosides. The phospha nucleoside analogues were tested against HCV, but did not show any antiviral activity at a 10 μM maximum concentration used for the inhibition assays of analogues 2-T, 2-C and 4-Tα.     

Synthesis of 3′-azido-4′-ethynyl-3′,5′-dideoxy-5′-norarabinouridine: a new anti-HIV nucleoside analogue

3′-Azido-4′-ethynyl-3′,5′dideoxy-5′-norarabinouridine 10 was synthesized from commercial uridine 1 in which the key step is the opening of protected 2′,3′-epoxyuridine derivative 7 by sodium azide and the hydroxymethyl at 4-position of the ribose ring are replaced by ethynyl group.     

Synthesis of 5,5′-diarylated 2,2′-bithiophenes via palladium-catalyzed arylation reactions

2,2′-Bithiophene and 3,3′-dicyano-2,2′-bithiophenes are diarylated directly with aryl bromides at the 5- and 5′-positions accompanied by C-H bond cleavage in the presence of Pd(OAc)₂ and a bulky phosphine ligand using Cs₂CO₃ as base. In the reaction using (2,2′-bithiophen-5-yl)diphenylmethanol as the substrate, monoarylation at the 5-position via C-C bond cleavage occurs selectively to give 5-aryl-2,2′-bithiophenes and the subsequent arylation with a different aryl bromide affords the corresponding unsymmetrically 5,5′-diarylated products.     

General method for the synthesis of 2′-O-carboranyl-nucleosides

The carboranyl cage is a new modifying entity for nucleosides, DNA oligonucleotides, and other biomolecules. Herein, the first reliable method for the synthesis of nucleosides modified with a carborane cluster at the 2′-position is described.     

A simple synthetic approach to homochiral 6- and 6′-substituted 1,1′-binaphthyl derivatives

Various homochiral binaphthyl derivatives having functional groups at the 6-position are important key intermediates for the immobilization of binaphthyl compounds on various solid-supports and have been prepared from commercially available 1,1′-bi-2-naphthol via controlled monopivalation of the 2-hydroxyl group and electrophilic aromatic substitution at the 6-position. (S)-2,2′-Bis-((S)-4-alkyloxazol-2-yl)-6-(2-methoxycarbonyl)ethyl-1,1′-binaphthyls (6-functionalized (S,S)-boxax)) were prepared and immobilized on various polymer supports including PS-PEG, PS, PEGA and MeO-PEG resin.     

An efficient synthesis of 5,5′-diaryl-2,2′-bichalcophenes

A convenient and high yielding synthesis of 5,5′-diaryl-2,2′-bichalcophenes (furans, thiophenes, and selenophenes) by the hexabutylditin-mediated homocoupling of 5-bromochalcophenes is described. This approach has been applied to the synthesis of the blue-light-emitting compound 5,5′-bis(4-aminophenyl)-2,2′-bifuryl (PFDA).     

Synthesis of (±)-4′-ethynyl-5′,5′-difluoro-2′,3′-dehydro-3′-deoxy- carbocyclic thymidine: a difluoromethylidene analogue of promising anti-HIV agent Ed4T

Synthesis of (±)-4′-ethynyl-5′,5′-difluoro-2′,3′-dehydro-3′-deoxy-carbocyclic-thymidine (8) was carried out. The difluoromethylylidene group of 8 was constructed by the electrophilic fluorination to the cyclopentenone 11 by using Selectfluor^®. Introduction of thymine base was investigated based on the Mitsunobu reaction by employing cyclopentenyl allyl alcohols variously substituted at the 4-position. It was found the 4-methoxycarbonyl derivative 14 gave the highest selectivity both in terms of regio- and stereochemistry.     

Synthesis of 2′,3′-dideoxy-6′,6′-difluoro-3′-azanucleosides

The straightforward synthesis of four novel 2′,3′-dideoxy-6′,6′-difluoro-3′-azanucleosides 1a-d is described. Efficient construction of the fluorine-containing pyrrolidine ring through two different ways and installation of pyrimidine rings using the amino groups in the intermediates 12, 26 were the key steps of our synthesis.     

A versatile reagent for the synthesis of 5′-phosphorylated, 5′-thiophosphorylated or 5′-phosphoramidate-conjugated oligonucleotides

We report the synthesis of a new phosphorylating reagent that is easily accessible and allows not only the chemical synthesis of 5′-phosphorylated and 5′-thiophosphorylated oligonucleotides but also the 5′-conjugation through a phosphoramidate linkage. 5′-Amino-linker and 5′-alkyne oligonucleotides were obtained and the latter was conjugated by a 1,3-dipolar cycloaddition (click chemistry) with a galactosylated azide derivative to afford 5′-galactosyl oligonucleotide with high efficiency.     

5,5′-二甲基-2,2′-二茚满-1,1′,3,3′-四酮的合成及结构表征

本文以4-甲基邻苯二甲酸酐为原料, 成功地合成了5,5′-二甲基-2,2′-二茚满-1,1′,3,3′-四酮(2). 通过元素分析、核磁共振、红外光谱及质谱等测试手段, 确定了化合物2的结构与存在形式, 通过ESR测试发现化合物2具有顺磁性.     

Synthesis,spectral, thermal and BVS investigations on ZnS4N^N/N coordination environment: Single crystal X-ray structures of bis(dibenzyldithiocarbamato)(N^N)Zinc(II) complexes (N^N = 1,10-phenanthroline,tetramethylethylenediamine and 4,4′-bipyridine)

The current paper describes the synthesis and spectral investigations on the adducts of [Zn(dbzdtc)₂] (1) with 1,10-phen (2), tmed (3), 2,2′-bipy (4) and 4,4′-bipy (5) (where, dbzdtc = dibenzyldithiocarbamate anion, 1,10-phen = 1,10-phenanthroline, tmed = tetramethylethylenediamine, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridne) and single crystal X-ray structures of [Zn(dbzdtc)₂(1,10-phen)] (2) and [Zn(dbzdtc)₂(tmed)] (3) and [Zn(dbzdtc)₂(4,4′-bipy)] (5). ¹H and ¹³C NMR spectra of 1,10-phen, tmed, 2,2′-bipy and 4,4′-bipy adducts were recorded. ¹H NMR spectra of the complexes show the drift of electrons from the nitrogen of the substituents forcing a high electron density towards sulfur via the thioureide π-system. In the ¹³C NMR spectra, the most important thioureide (N¹³CS₂) carbon signals are observed in the region: 206–210 ppm. Fluorescence spectra of complexes (2) and (4) show intense fluorescence due to the presence of rigid conjugate systems such as 1,10-phenanthroline and 2,2′-bipyridine. The observed fluorescence maxima for complexes with an MS₄N₂ chromophore in the visible region are assigned to the metal-to-ligand charge transfer (MLCT) processes. Single crystal X-ray structural analysis of (2) and (3) showed that the zinc atom is in a distorted octahedral environment. Bond Valence Sum was found to be equivalent to 1.865 for (2), 1.681 for (3) supporting the correctness of the determined structure. BVS of (3) deviates from the formal oxidation number of zinc due to the non-aromatic, sterically hindering tetramethyl bonding end of tmed. Thermal studies on the compounds show the formation of Zn(NCS)₂ as an intermediate during the decay.     

Synthesis of 1′-fluorouracil nucleosides as potential antimetabolites

The first synthesis of 1′-fluoronucleosides, which has long been synthetic targets as the potential antimetabolites, was achieved. Electrophilic fluorination of the 1′-position occurred to form an anomeric mixture of 1′-fluorouridine derivatives, when the lithium enolate, prepared from 3′,5′-O-tetraisopropyldisiloxane-1,3-diyl (TIPDS)-protected 2′-ketouridine (10) and LiHMDS, was treated with an electrophilic fluorinating agent such as NFSI (13). Subsequent reduction of the 2′-keto-moiety of the resulting β-nucleoside gave the protected 1′-fluorouridine 16 and its arabino-type congener 17. Alternatively, nucleophilic fluorination was also successful. Thus, treatment of 2′,3′,5′-tri-O-acetyl-1′-phenylselenouridine (20) with DAST/NBS produced the 1′-fluorouridine triacetate (21) and its α-anomer 22.     

Synthesis, structure and electrochemistry of cationic diruthenium complexes of the type [(N∩N)2Ru2(CO)2(μ-CO)2(μ-OOCFc)] containing a ferrocenecarboxylato bridge and two chelating aromatic diimine ligands

The dinuclear bis(ferrocenecarboxylato) complex Ru₂(CO)₄(μ-OOCFc)₂(py)₂ (Fc = ferrocenyl, py = pyridine) was found to react with aromatic diimines (2,2′-dipyridyl, 4,4′-dimethyl-2,2′-dipyridyl, 1,10-phenanthroline, 5-nitro-1,10-phenanthroline, and 5-amino-1,10-phenanthroline) in methanol to give the cationic diruthenium complexes [(N∩N)₂Ru₂(CO)₂(μ-CO)₂(μ-OOCFc)]⁺ (1: N∩N = 2,2′-dipyridyl, 2: N∩N = 4,4′-dimethyl-2,2′-dipyridyl, 3: N∩N = 1,10-phenanthroline, 4: N∩N = 5-nitro-1,10-phenanthroline, 5: N∩N = 5-amino-1,10-phenanthroline), which have been isolated as the hexafluorophosphate salts. The molecular structure of 3, solved by single-crystal X-ray analysis of the tetraphenylborate salt [3][BPh₄], shows a diruthenium backbone bridged by two carbonyl and by one ferrocenecarboxylato ligand, the two 1,10-phenanthroline ligands being in the axial positions. Cyclic voltammetry in dichloromethane reveals for all compounds two successive oxidations due to ferrocene/ferrocenium redox couple and oxidation of the diruthenium core.     

A general and efficient route to 3′-deoxy-3′-N-, S-, and C-substituted altropyranosyl thymines from 2′,3′-O-anhydro-mannopyranosylthymine

An efficient route to 1-(2,3-O-anhydro-4,6-O-phenylmethylene-β-d-mannopyranosyl) thymine from 1,2,4,6-tetra-O-acetyl-3-O-tosyl-β-d-glucopyranose has been devised. This newly synthesized epoxide is opened up regioselectively at the C-3′-position by N-, S-, and C-nucleophiles to afford a wide range of new 3′-deoxy-3′-substituted altropyranosyl thymines.     

An efficient synthesis of new 1-H-4′-methyl-3′,4′-dihydrospiro[piperidine-4,2′(1′H)quinoline] scaffolds

Efficient synthesis of new 3′,4′-dihydrospiro[piperidine-4,2′(1′H)quinolines] by a four step synthetic route based on 1-benzyl-4-piperidone reactivity is reported.     

A facile synthesis of cyclic bis(3′→5′)diguanylic acid

This paper describes a new method for synthesizing biologically important cyclic bis(3′→5′)diguanylic acid (cGpGp) in a higher yield than that of the existing synthetic method. In the new synthesis, the following two means, in place of those used in the existing synthesis are employed as main strategies to cause the increase in product yield. One of these distinctive strategies in the new synthesis is that the phosphoramidite method is used for the preparation of a key synthetic intermediate of a linear guanylyl(3′→5′)guanylic acid derivative. This method allowed higher-yield formation of the intermediate than that by the triester method used in the existing synthesis. The second distinctive strategy used in the new synthesis is that allyloxycarbonyl and allyl groups are used for the protection of two guanine bases and two internucleotide bonds, respectively. These four allylic protectors can be removed all at once by the organopalladium-catalyzed reaction under neutral conditions. Thus, deprotection of the protected cGpGp precursor was achieved in the present synthesis in a shorter step and under milder conditions than the deprotection achieved in the existing synthesis, which uses diphenylacetyl and o-chlorophenyl groups as protectors for two guanine bases and two internucleotide bonds, respectively, whose full removal requires two different procedures including rather harsh basic treatment. As a result, technical loss and decomposition of the target product in the new synthesis is remarkably reduced.