Biphenomycin B and Derivatives: Total Synthesis and Translation Inhibition

A full account on the synthesis of the antibiotic natural product biphenomycin B and several derivatives is reported, which employs a Suzuki coupling reaction of a free carboxylic acid and macrolactam formation as key transformations. Liberal exchange of the central amino acid was demonstrated. This procedure gave derivatives to study the influence of the polar side chain of the central amino acids on translation inhibition.     

Organotin catalysts in organosilicon chemistry

Organotin compounds are best known in the chemical industry as PVC stabilizers, polyurethane foam formers and antifungal agents. However, they have also been widely used in the silicon industry for decades for curing organosilicon polymers, despite the fact that neither the mechanism through which the siloxane bonds are formed nor their inherent toxicity are completely understood. This review gives an account of the use of organotin compounds in the preparation of diverse polysiloxane‐containing materials via cross‐linking with either organic or inorganic polymers. As they are common ingredients for this application, a brief outline of the preparation of relevant silicon‐containing compounds, as well as their reactivity, are given. In addition, since there is some evidence that stannasiloxanes formed in situ during the reaction play a determinant role as intermediates in the reaction mechanism, an overview of the synthesis and reactivity of Sn‐O‐Si‐containing compounds is also presented. Copyright © 2012 John Wiley & Sons, Ltd.     

Tetrathiafulvalene–Oligo(para‐phenyleneethynylene) Conjugates: Formation of Multiple Mixed‐Valence Complexes upon Electrochemical Oxidation

Short monodisperse oligo‐ (para‐phenyleneethynylene) (pOPE) units bearing laterally attached tetrathio‐substituted tetrathiofulvalene (TTF) units have been synthesised from functionalised aromatic building blocks by using the Sonogashira cross‐coupling methodology. The unusual redox properties of these TTF–pOPE conjugates were observed by employing electrochemical methods, such as cyclic voltammetry and exhaustive electrolysis. We found that formally one half of the TTF units in the pOPE monomer 1 , dimer 2 , and trimer 3 (with 2, 4, and 6 TTF units, respectively) are electrochemically silent during the first‐step oxidation at 0.49 V. We propose the formation of persistent mixed‐valence complexes from the TTF and TTF^+. units present in an equal ratio. Such mixed‐valence dyads (single or multiple in the partially oxidised 1 – 3 ) exhibit an unusual stability towards oxidation until the potential of the second oxidation at 0.84 V is achieved. This finding suggests that below this potential the oxidation of the respective mix‐valence complexes is extremely slow.     

The development of phosphinoamine–Pd(II)–imidazole complexes: implications in room‐temperature Suzuki–Miyaura cross‐coupling reaction

The reaction of N‐methylimidazole (N‐MeIm) and N‐butylimidazole (N‐BuIm) with the complexes [PdCl₂(PPh₂py–P,N)] and [PdCl₂(PPh₂Etpy–P,N)] in the presence of NH₄PF₆ under N₂ at room temperature afforded four new cationic Pd(II) complexes [PdCl(PPh₂py–P,N)(N‐MeIm)](PF₆) ( 1 ), [PdCl(PPh₂py–P,N)(N‐BuIm)](PF₆) ( 2 ), [PdCl(PPh₂Etpy–P,N)(N‐MeIm)](PF₆) ( 4 ) and [PdCl(PPh₂Etpy‐P,N)(N‐BuIm)](PF₆) ( 5 ) in good yields, where PPh₂py is 2‐(diphenylphosphino)pyridine and PPh₂Etpy is 2‐{2‐(diphenylphosphino)ethyl}pyridine). The complexes were fully characterized. The catalytic activities of these complexes were investigated for Suzuki–Miyaura cross‐coupling reactions at room temperature. Complex 2 exhibited excellent activity compared to other analogs. Copyright © 2013 John Wiley & Sons, Ltd.     

Heteroacene Synthesis through C−S Cross‐Coupling/5‐endo‐dig Cyclization

Highly efficient, one‐step synthesis of sulfur‐containing heteroacenes was achieved through palladium‐catalyzed C?S cross‐coupling of bis‐alkynes with thioacetate as hydrogen sulfide surrogate. Heteroacenes consisting of three, five, and seven fused aromatic rings were obtained in a single catalytic step by four‐, six‐, and eightfold C?S bond formation.     

Asymmetric Suzuki–Miyaura Cross‐Coupling for the Synthesis of Chiral Biaryl Compounds as Potential Monophosphine Ligands

Efficient asymmetric Suzuki–Miyaura coupling reactions have been employed for the first time to synthesize chiral biaryl compounds with phosphinate groups as chiral auxiliaries. A series of functionalized chiral biaryls are thereby synthesized in excellent yields and good diastereoselectivities (up to >95:5 d.r.) and axially chiral monophosphorus ligands are obtained through further functionalizations.     

Design and Synthesis of a New Family of Fluorinated Liquid Crystals

A convenient and simple three‐step pathway to the new family of CF₂CF₂S‐bridged alkanes and CF₂S‐, CF₂O‐bridged alkenes and alkynes was elaborated by using catalytic olefination reaction as a key step of the synthetic sequence. The obtained compounds revealed attractive liquid crystalline characteristics.     

Ionic iron(III) complexes bearing a dialkylbenzimidazolium cation: Efficient catalysts for magnesium‐mediated cross‐couplings of aryl phosphates with alkyl bromides

A series of ionic iron(III) complexes of general formula [HLⁿ ][FeX₄] (HL¹ = 1,3‐dibenzylbenzimidazolium cation, X = Cl, 1 ; HL¹, X = Br, 2 ; HL² = 1,3‐dibutylbenzimidazolium cation, X = Br, 3 ; HL³ = 1,3‐bis(diphenylmethyl)benzimidazolium cation, X = Br, 4 ) were easily prepared in high yields by the direct reaction of FeX₃ with 1 equiv. of [HLⁿ ]X under mild conditions. All of them were characterized using elemental analysis, Raman spectroscopy and electrospray ionization mass spectrometry, and X‐ray crystallography for 1 and 4 . In the presence of magnesium turnings and LiCl, these air‐ and moisture‐insensitive complexes showed high catalytic activities in direct cross‐couplings of aryl phosphates with primary and secondary alkyl bromides with broad substrate scope, wherein complex 4 was the most effective.