Interaction of hydrogen peroxide and thiourea or its oxides with terephthalic acid

The suitability of thiourea and its oxides for the hydroxylation of terephthalic acid in aqueous solutions was explored. Allsulfur-containing compounds tested were found to favor the formation of hydroxyterephthalic acid. It was shown that thiourea and its di- and trioxides can act as both traps and promoters of hydroxyl radicals in aqueous solutions.     

Fragmentation behavior of a thiourea‐based reagent for protein structure analysis by collision‐induced dissociative chemical cross‐linking

The fragmentation behavior of a novel thiourea‐based cross‐linker molecule specifically designed for collision‐induced dissociation (CID) MS/MS experiments is described. The development of this cross‐linker is part of our ongoing efforts to synthesize novel reagents, which create either characteristic fragment ions or indicative constant neutral losses (CNLs) during tandem mass spectrometry allowing a selective and sensitive analysis of cross‐linked products. The new derivatizing reagent for chemical cross‐linking solely contains a thiourea moiety that is flanked by two amine‐reactive N‐hydroxy succinimide (NHS) ester moieties for reaction with lysines or free N‐termini in proteins. The new reagent offers simple synthetic access and easy structural variation of either length or functionalities at both ends. The thiourea moiety exhibits specifically tailored CID fragmentation capabilities—a characteristic CNL of 85 u—ensuring a reliable detection of derivatized peptides by both electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization (MALDI) tandem mass spectrometry and as such possesses a versatile applicability for chemical cross‐linking studies. A detailed examination of the CID behavior of the presented thiourea‐based reagent reveals that slight structural variations of the reagent will be necessary to ensure its comprehensive and efficient application for chemical cross‐linking of proteins. Copyright © 2010 John Wiley & Sons, Ltd.     

The influence of the type of halogen substituent and its position on the molecular conformation,intermolecular interactions and crystal packing for a series of 1‐benzoyl‐3‐(halogenophenyl)thioureas

By the reaction of benzoyl chloride, potassium isothiocyanate and the appropriate halogenoaniline, i.e. 2/3/4‐(bromo/iodo)aniline, we have obtained five new 1‐benzoyl‐3‐(halogenophenyl)thioureas, namely, 1‐benzoyl‐3‐(2‐bromophenyl)thiourea and 1‐benzoyl‐3‐(3‐bromophenyl)thiourea, C₁₄H₁₁BrN₂OS, and 1‐benzoyl‐3‐(2‐iodophenyl)thiourea, 1‐benzoyl‐3‐(3‐iodophenyl)thiourea and 1‐benzoyl‐3‐(4‐iodophenyl)thiourea, C₁₄H₁₁IN₂OS. Structural and conformational features of the compounds have been analyzed using X‐ray diffraction and theoretical calculations. The novel compounds were characterized by solid‐state IR and ¹H/¹³C NMR spectroscopy. The conformations and intermolecular interactions, such as hydrogen bonds, π–π and S(6)…π stacking, and X…O (X = I or Br), I…S and I…π, have been examined and rationalized, together with four analogous compounds described previously in the literature. The set of nine compounds was chosen to examine how a change of the halogen atom and its position on the phenyl ring affects the molecular and crystal structures.     

Synthesis,Chemical Characterization,DNA Interaction and Antioxidant,Studies of New Nitrosubstituted Thioureas and Their Copper Complexes

In the present work new nitro substituted thioureas, and their copper complexes have been synthesized and characterized by FTIR and multinuclear NMR techniques. Some of the compounds namely 1‐benzoyl‐3‐(4‐chloro‐3‐nitrophenyl) thiourea (A‐1), 1‐benzoyl‐3‐(4‐chloro‐3‐nitrophenyl) thiourea (A‐2) and 1‐benzoyl‐3‐(2‐methoxy‐4‐nitrophenyl) thiourea (A‐2) have also been characterized by single crystal XRD. All the synthesized compounds have been screened for DNA binding potencies (using cyclic voltametry, UV‐vis spectroscopy) and free radical scavanging activities.     

An Efficient Route to Nanostructured Tungsten Oxide Films with Improved Electrochromic Properties

An effective chemical route to nanostructured tungsten oxide films derived from a peroxopolytungstic acid (PTA)/thiourea precursor solution is demonstrated. The conventional procedure of preparing the precursor needs more than 24 h for well‐mixing and refluxing the PTA‐based solution, while the thiourea‐assisted approach takes less than 1 h to prepare the precursor solution because the excess hydrogen peroxide can be efficiently eliminated by oxidation of thiourea. With the precursor solution, tungsten oxide films are deposited by spin coating followed by high temperature annealing. The film annealed at 400 °C possesses a porous nanostructure of nanocrystalline tungsten oxide embedded in an amorphous tungsten oxide matrix, which arises from the gaseous species released through decomposition of thiourea oxides during annealing. The 400 °C‐annealed, thiourea‐assisted tungsten oxide film exhibits electrochromic (EC) properties superior to those of the film prepared without thiourea, including large transmittance modulation and coloration efficiency, fast response time and adequate reliability. When increasing the annealing temperature to 450 °C, the thiourea‐assisted tungsten oxide film is also porous but well‐crystallized and shows inferior EC properties. Electrochemical impedance spectroscopy analysis indicates that, in addition to the porous structure, a fast charge‐transport rate within the solid portion of the 400 °C‐annealed nanostructured film plays a crucial role in enhancing EC performances of the thiourea‐assisted tungsten oxide film.     

Synthèses stéréosélectives de deux trioxydes C18H30O3 stéréo-isomères,d'ambréinolide et de sclaréol-lactone à partir de dérivés du (+)-manool

Ambreinolide, sclareol-lactone and a pair of new trioxides C₁₈H₃₀O₃ have been synthesized from suitable derivatives of (+)-manool through stereoselective reactions.     

N‐Glycosyl‐N′‐[p‐(isoamyloxy)phenyl]‐thiourea Derivatives: Potential Anti‐TB Therapeutic Agents

Thiocarlide (THC; N,N′‐bis[p‐(isoamyloxy)phenyl]‐thiourea; also known as Isoxyl^®) has been used in the past as an anti‐tuberculosis agent. In an effort to improve the therapeutic value of THC, several N‐glycosyl‐N′‐[p‐(isoamyloxy)phenyl]‐thiourea derivatives were synthesized by coupling an aniline derivative and glycosyl isothiocyanates. The minimum inhibitory concentration (MIC) values of the new products against M. tuberculosis were determined.     

Brønsted Acid Catalyzed Morita–Baylis–Hillman Reaction: A New Mechanistic View for Thioureas Revealed by ESI‐MS(/MS) Monitoring and DFT Calculations

A Morita–Baylis–Hillman (MBH) reaction catalyzed by thiourea was monitored by ESI‐MS(/MS) and key intermediates were intercepted and characterized. These intermediates suggest that thiourea acts as an organocatalyst in all steps of the MBH reaction cycle, including the rate‐limiting proton‐transfer step. DFT calculations, performed for a model MBH reaction between formaldehyde and acrolein with trimethylamine as base and in the presence or the absence of thiourea, suggest that thiourea accelerates MBH reactions by decreasing the transition‐state (TS) energies through bidentate hydrogen bonding throughout the whole catalytic cycle. In the rate‐limiting proton‐transfer step, the thiourea acts not as a proton shuttle, but as a Brønsted acid stabilizing the basic oxygen center that is formed in the TS.     

High-temperature tungsten trioxides obtained by concentrated solar energy: physicochemical and electrochemical characterization

Journal of Solid State Electrochemistry - High-crystalline tungsten trioxides (WO3) have been synthesized by an environmentally friendly method using concentrated solar energy. The obtained...     

Synthesis and Chemistry of Endoperoxides Derived from 3,4‐Dihydroazulen‐1(2H)‐one: An Entry to Cyclopentane‐Anellated Tropone Derivatives

Reduction of trienone 1 and subsequent treatment with acid in MeOH furnished 1‐methoxy‐1,2,3,4‐tetrahydroazulene ( 13 ). Photo‐oxygenation of 13 provided the two bicyclic endoperoxides 14 and 15 . Pyrolysis of 14 and 15 gave the corresponding bis‐epoxides 17 and 18 , which have been synthesized also upon treatment with a catalytic amount of CoTPP (TPP=tetraphenylporphyrin). That an unusual endoperoxide‐endoperoxide rearrangement has not been observed strongly supports the assumption that the carbonyl group in 2 – 4 is responsible for this unprecedented endoperoxide‐endoperoxide rearrangement. Treatment of the endoperoxides 14 and 15 with a catalytic amount of Et₃N at 0° provided the azulenones 22 and 23 in high yield. Attempted cleavage of the O−O peroxide linkage in 14 and 15 with thiourea resulted, contrary to our expectation, in the formation of 22 and 23 . That thiourea acts as a base instead of a reducing reagent has been observed for the first time in peroxide chemistry.     

Enantioselective Allylic Amination of Morita‐Baylis‐Hillman Acetates Catalyzed by Chiral Thiourea‐Phosphine

The enantioselective allylic amination of Morita‐Baylis‐Hillman acetates catalyzed by chiral cyclohexane‐based thiourea‐phosphine catalysts was investigated. In the presence of 20 mol% rosin‐derived thiourea‐phosphine 3j , the chiral amines were obtained in up to 88% yield and up to 85% ee.     

Efficient construction of C–C bonds from aryl halides/aryl esters with arylboronic acids catalysed by palladium(II) thiourea complexes

A new set of palladium(II) complexes comprising phenyl(thiazolyl)thiourea ligands have been successfully synthesized and characterized with the aid of analytical as well as spectral (IR, UV–visible and NMR) methods. A distorted square‐planar geometry with N^S coordination mode of thiourea ligands in the new palladium complexes was corroborated by single‐crystal X‐ray diffraction methods. Interestingly, the palladium(II) thiourea complexes showed the highest catalytic activity with 0.1 mol% catalyst loading in Suzuki–Miyaura cross‐coupling reactions utilizing a range of aryl bromides/unactivated aryl chlorides with arylboronic acids as coupling partners in aqueous–organic media. Syntheses of diaryl ketones using aryl esters and arylboronic acids as coupling partners were also achieved with low catalyst loading within 20 h. The potential of our catalyst was demonstrated by its wide substrate scope, low catalyst loadings and high isolated yield. Moreover, the influences of key parameters like solvent, base, temperature and catalyst loading were also investigated.     

Highly Enantioselective Intramolecular Morita‐Baylis‐Hillman Reaction Catalyzed by Mannose‐Based Thiourea‐phosphine

The saccharide‐based chiral bifunctional thiourea‐phosphines were developed as chiral organocatalysts for the intramolecular Morita‐Baylis‐Hillman reaction of ω‐formyl‐enones. With only 2 mol% of thiourea‐phosphine catalyst 3c , chiral functionalized cyclohexenes were achieved under mild reaction conditions with excellent yields and enantioselectivities.     

Electrochemistry Broadens the Scope of Flavin Photocatalysis: Photoelectrocatalytic Oxidation of Unactivated Alcohols

Riboflavin‐derived photocatalysts have been extensively studied in the context of alcohol oxidation. However, to date, the scope of this catalytic methodology has been limited to benzyl alcohols. In this work, mechanistic understanding of flavin‐catalyzed oxidation reactions, in either the absence or presence of thiourea as a cocatalyst, was obtained. The mechanistic insights enabled development of an electrochemically driven photochemical oxidation of primary and secondary aliphatic alcohols using a pair of flavin and dialkylthiourea catalysts. Electrochemistry makes it possible to avoid using O₂ and an oxidant and generating H₂O₂ as a byproduct, both of which oxidatively degrade thiourea under the reaction conditions. This modification unlocks a new mechanistic pathway in which the oxidation of unactivated alcohols is achieved by thiyl radical mediated hydrogen‐atom abstraction.     

Zinc Coordination Complex for use in Uniform ZnS Microflowers Synthesis

Uniform snowball zinc sulfide (ZnS) microflowers with nanosheet covering were synthesized using the one step reaction of zinc coordination compounds with thiourea at 160 °C for 24 h. X‐ray single crystal diffraction, electron microscopy, energy‐dispersive X‐ray spectrometry, and X‐ray diffraction were used to characterize the products. The flower‐like ZnS crystals may have some application in catalyst or solar cell devices. This work is also expected to be applied in the fabrication of other transition metal sulfide crystals with special morphology.     

Preparation of Silver Nanoparticles‐Based Sensors for the Electrochemical Detection of Thiourea in Leaching Solutions of Waste Electrical and Electronic Equipment

Waste of electrical and electronic equipment is an interesting secondary resource of base and precious metals. Particularly the use of thiourea‐leaching in acidic medium was proposed for noble metals recovery. In this work, a novel and easy‐to‐use electrochemical sensor was developed, aimed to test thiourea from leaching solutions containing significant thiourea and copper amounts. The sensor was constructed using silver nanoparticles (AgNPs) deposited on screen‐printed electrodes. Its performance was studied in a synthetic leaching solution; changes in the overall surface charge of AgNPs resulting in changes in the charge‐transfer resistance for the copper ions were evaluated by electrochemical impedance spectroscopy.     

2,6‐Diaryl‐4,4‐disubstituted‐4H‐thiopyran: Source for spiro heterocycles

The 1,5‐diaryl‐3,3‐disubstituted‐1,5‐pentanedione on reaction with ammonium acetate, phosphorus pentoxide and phosphorus pentasulfide gave respective 1,4‐dihydropyridine, 4H‐pyran and 4H‐thiopyran. Novel spiro heterocycles have been obtained by the cyclocondensation of 4H‐thiopyran with hydrazine, hydroxylamine, urea and thiourea.     

Synthesis and Metal Complexes of Thiourea Ligands Containing Carbohydrate‐Derived Substituents

Two glucose‐derived thiourea derivatives, 2a and 2b , were prepared by addition of the corresponding amino sugars to a solution of 4‐nitrobenzoyl isothiocyanate (Scheme 1). The thioureas were isolated as colorless solids in good yields and were fully characterized by NMR spectroscopy, optical rotation, elemental analysis, and also by single‐crystal X‐ray diffraction. Attempts to obtain Cu^II and Ni^II bis(chelate) complexes with these thioureas failed. However, the C(1)‐protected thiourea derivative 2a reacted with orthopalladated acetato‐bridged dimers to afford the corresponding monomeric Pd^II complexes 3 and 4 (Scheme 2). In these compounds, the thiourea coordinates to the metal as monoanionic O,S chelate ligand, which was confirmed by X‐ray crystallography.     

Catalytic Thiourea Promoted Electrophilic Thiocyanation of Indoles and Aromatic Amines with NCS/NH4SCN

A simple and efficient protocol for the electrophilic thiocyanation of indoles and aromatic amines with thiourea/NCS/NH₄SCN system has been developed. The major features of the present procedure are the mild conditions, good yields, short reaction times, and the use of inexpensive and readily available organocatalyst. Moreover, N‐chlorosuccinimide (NCS) was found to be indispensable, and thiourea could greatly promote the reaction.     

Enantioselective Sulfur‐Michael Addition of Thioacetic Acid to Nitroalkenes Catalyzed by Bifunctional Amine‐Thiourea Catalysts

An enantioselective Michael addition of thioacetic acid (AcSH) to nitroalkenes, catalyzed by a leucine‐derived bifunctional amine? thiourea, was developed with high yields and moderate enantioselectivities. The thiourea‐ammonium salt formed in the reaction is identified as the active catalyst, and the multiple H‐bonding system is responsible for the stereocontrol. The resulting thioester products are useful intermediates for the synthesis of enantiomerically enriched S‐containing compounds.