Intramolecular Aryl Migration of Diaryliodonium Salts: Access to ortho‐Iodo Diaryl Ethers

By using vicinal trifluoromethanesulfonate‐substituted diaryliodonium salts, a novel approach was developed for the synthesis of ortho‐iodo diaryl ethers by intramolecular aryl migration. The reaction conditions are mild with a broad substrate scope. Mechanistic insight suggests a sulfonyl‐directed nucleophilic aromatic substitution pathway. Additionally, the product ortho‐iodo diaryl ethers serve as versatile synthons as demonstrated with several coupling reactions. Furthermore, a useful thyroxine analogue of the 3‐iodo‐l ‐thyronine (3‐T₁) derivative was synthesized by this aryl migration procedure.     

An Efficient Synthesis of Diaryl Ethers by Coupling Aryl Halides with Substituted Phenoxytrimethylsilane in the Presence of TBAF

A general synthesis of diaryl ethers via coupling of aryl halides with substituted phenoxytrimethylsilane in the presence of TBAF is described. The protocol is simple and mild, and gives good to excellent yields.     

Nonconventional Stereochemical Issues in the Design of the Synthesis of the Vancomycin Antibiotics: Challenges Imposed by Axial and Nonplanar Chiral Elements in the Heptapeptide Aglycons

Controlling the elements of planar and axial chirality are the principal challenges in the synthesis of the aglycon of vancomycin. Vancomycin is the prototypical member of the glycopeptide family of antibiotics which are effective for the treatment of infections by methicillin-resistant Staphylococcus aureus. The first total syntheses of the vancomycin and eremomycin aglycons provide insight into the influence of structure on kinetic and thermodynamic control of atropselective macrocyclizations.     

Synthesis of RHPS4 via an anionic ring closing cascade

A new and convergent synthesis of the potent telomerase inhibitor RHPS4 is presented. The key step is the construction of the pentacyclic framework via an anionic ring closing cascade in which two new rings are formed.     

A Rapid and Efficient Synthesis of Diaryl Thioureas via Solvent-Free Reaction Using Microwave

The application of microwave techniques for chemical synthesis has attracted considerable interest in recent years1-5. The reason is that technology can enhance the selectivity and reactivity6,7, increase the chemical yields and shorten the reaction time8,9. In order to provide a method that is economic, without pollution, easy to carry out, we coupled the solvent-free reaction with microwave.As we know, thiourea compounds are associated with a serious biological activities such as antiviral10…     

New Type of Lariat Ethers: Synthesis and Cation Binding Ability of Phosphonoalkyl-Azacrown Ethers

The synthesis of azacrown ethers with phosphonoalkyl side chains of two to five carbon atoms ( 3–8, 10), potentially useful as a new type of cation binding agent, is described. Introduction of the phosphonoalkyl moiety into the parent monoaza-15-crown-5 ( 1) decreases the cation extraction ability, but results in an increase in the selectivity towards the cations examined. The effect of the phosphonoalkyl-azacrown ethers on the properties of membranes used in ion-selective electrodes is also reported.     

Nucleophilic Reactivity of Ethers Against Terminal Epoxides in the Presence of BF3: A Mechanistic Study

In the presence of BF₃, a series of symmetrical and unsymmetrical ethers reacted with epichlorohydrin and 2‐[(benzyloxy)methyl]oxirane, two terminal epoxides, to afford 1‐alkoxy‐3‐chloropropan‐2‐ol and 1‐alkoxy‐3‐(benzyloxy)propan‐2‐ol. The cleavage of unsymmetrical ethers occurred via an S_N2 or S_N1 mechanism. Secondary epoxides did not give similar ring‐opening products.     

Synthesis of Highly Functionalized Diaryl Ethers by Copper‐Mediated O‐Arylation of Phenols using Trivalent Arylbismuth Reagents

Highly functionalized diaryl ethers were prepared by copper(II) acetate mediated O‐arylation reaction of phenols using trivalent organobismuthanes. The reaction is performed under simple conditions and tolerates a wide diversity of functional groups on the phenol and on the organobismuth reagent. Substoichiometric amounts of catalyst can be used by performing the reaction under an oxygen atmosphere. The N‐arylation of pyridones is also reported.     

Twenty-five Years of "Crowning" Around: Synthesis of Crown Ethers at Brigham Young University

A review of the synthesis of crown ethers at Brigham Young University ispresented. Topics include: thiacrown ethers, diestercrown ethers,proton-ionizable crown ethers, chiral crown ethers, azacrown ethers,cryptands and other polycyclic ligands, and the Mannich reaction method toprepare azacrown ethers and cryptands.     

Direct Amination of meso‐Tetraarylporphyrin Derivatives – Easy Route to A3B‐, A2BC‐, and A2B2‐Type Porphyrins Bearing Two Nitrogen‐Containing Substituents at the meso‐Positioned Phenyl Groups

meso‐Tetraarylporphyrinato complexes 1a – g (Zn^II, Cu^II, and Ni^II) bearing one or two nitro‐substituted aryl moieties react with 1,1,1‐trimethylhydrazinium iodide in the presence of ^tBuOK in THF at 0–5° or in the presence of KOH in DMSO at 60–70° according to a nucleophilic substitution of an H‐atom, thus affording porphyrins 2a – g and 3f , g with amino‐functionalized meso‐positioned aryl substituents in yields up to 73% (Scheme 1 and Table). The products obtained are attractive intermediates for further derivatization of porphyrins and may be of potential use as sensitizers in photodynamic cancer therapy.     

Direct Preparation of Trifluoromethyl Ketones from Carboxylic Esters: Trifluoromethylation with (Trifluoromethyl)trimethylsilane

Previously difficult to prepare , aliphatic and alicyclic trifluoromethylketones (e.g. 1 and 2 ), which are of pharmacalogic interest as potential enzyme inhibitors, can now be synthesized easily and efficiently. The one-step reaction starting with carbonic esters and trimethyl(trifluoromethyl)silane is induced by tetrabutylammonium fluoride in nonpolar, aprotic solvents and proceeds without formation of double-addition products.     

Rhodium-Catalyzed Dimerization of Diaryl Acetylenes in the Presence of Grignard Reagents: Synthesis of 1,2,3-Triphenyl Naphthalene Derivatives

An efficient Rh-catalyzed dimerization of diaryl acetylenes was achieved in the presence of Wilkinson catalyst, AgF₂, and 1.5 equivalent of PhMgBr in toluene, providing the 1,2,3-triaryl naphthalene derivatives in moderate to good yields.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.     

Organometallic Compounds of Titanium and Zirconium as Selective Nucleophilic Reagents in Organic Synthesis

The addition of carbanionic organometallic compounds (usually RLi or RMgX) to a carbonyl group—a key step in numerous syntheses—is not always straightforward. Depending on the substrate, various complications and problems may arise, but in many cases these can be remedied by addition of (RO)₃TiCl, (RO)₃ZrCl or (R₂N)₃TiX to the classic lithium and Grignard reagents. This usually leads to formation of stable organo-titanium and -zirconium compounds which react highly selectively with carbonyl groups. For example, CH₃Ti(OiPr)₃ reacts five orders of magnitude faster with benzaldehyde than with acetophenone at room temperature; reagents of the type RTi(OiPr)₃ add smoothly to nitro-, ido-, or cyano-subsituted benzaldehyde, and the reactions may be performed in chlorinated solvents or acetonitrile; the zirconium analogues have particularly low basicity and add in high yield to α- and β-tetralones or to substrates containing a nitroaldol group; the inclusion of chiral OR^* groups gives enantioselective reagents (up to 90% ee); allylic (RO₃)Ti- derivatives react only at the more highly substituted carbon atom and, in addition, react diastereoselectively (up to 98% ds) with unsymmetrical ketones. Finally, titanium reagents have also been found to effect novel transformations such as direct geminal dialkylation (C?O→CMe₂) and alkylative amination [C?O→CR(NR)]. The modification and finetuning (“taming”) of carbonyl reactivity obtainable by use of the new reagents is not dearly bought; starting materials are the cheap and harmless “titanates”, “zirconates” and the corresponding tetrachlorides.     

An Easy Access to Oxime Ethers by Pd‐Catalyzed C—O Cross‐Coupling of Activated Aryl Bromides with Ketoximes and Chalcone Oximes

An efficient Pd‐catalyzed method for C—O cross‐coupling of ketoximes and chalcone oximes with activated aryl bromides and bromo‐chalcones has been developed. All oxime ethers were obtained in good to excellent yields by [(π‐allyl)PdCl]₂/tBuXPhos ( L7 ) catalyst system. TrixiePhos ( L11 ) was also found to be effective for the oxime coupling. This method offers an easy and smooth coupling of chalcone oximes with activated aryl bromides and bromo‐chalcones, which has not been previously explored.     

Palladium‐Catalyzed Arylation of (Di)azinyl Aldoxime Ethers by Aryl Iodides: Stereoselective Synthesis of Unsymmetrical (E)‐(Di)azinylaryl Ketoxime Ethers

The first example of direct arylation of (di)azinyl aldoxime ethers by aryl iodides is reported. The reaction produces, in a single step, a variety of geometrically pure unsymmetrical (E)‐(di)azinylaryl ketoxime ethers, a class of nitrogenated motifs that have found wide applications in medicinal and organic chemistry but are difficult to access using conventional procedure. The utility of the method is further illustrated in a formal synthesis of the Merck melanin‐concentrating hormone 1 receptor antagonist.     

Synthesis of novel 4-(2-amino-5-thiazolyl)-pyrimidine-2-amines as potential protein kinase inhibitors

Abstract  A short and efficient sequence for the synthesis of a series of 4-(2-amino-5-thiazolyl)-pyrimidine-2-amines was developed. 1-Phenyl-2-(6-pyrimidinyl)-ethanones, obtained via Weinreb’s methodology, were used in a Hantzsch thiazole cyclization reaction, followed by introduction of the aniline moieties via nucleophilic substitution. Graphical abstract        

Synthesis of Diaryl Ethers Through the Copper-Catalyzed Arylation of Phenols with Aryl Iodides Using KF/Al2O3

An efficient synthesis of diaryl ethers by the copper-catalyzed arylation of phenols with a variety of aryl iodide susing KF/Al₂O₃ as a suitable base and CuI and 1,3 diphenyl-1,3 propandione as the catalyst is described.