Nitroalkanes as new, ideal precursors for the synthesis of benzene derivatives

Nitroalkanes have emerged, in the past few years, as powerful acyclic building blocks to synthesize polyfunctionalized benzene derivatives, avoiding any serious regiochemical ambiguities due to the activating/deactivating and orienting effects of the substituents. Many of these procedures are realized in a one-pot process or a few-step sequence. This feature article describes recent results, mainly from our group, in this field.     

Characteristic features of crystal chemistry of natural mercury-containing sulfides and sulfosalts

Many mercury-containing minerals belonging to the class of sulfides and sulfosalts are based on a highly symmetric sphalerite type structure (ZnS), where both components occupy sites with high point symmetry providing stable orientation of directed interatomic interactions. Some structures of natural compounds of this type are used to demonstrate that the geometric matrix of cations and anions tends to be preserved during variation of the chemical composition caused by migration of elements under natural conditions. The fundamental laws of crystal formation are confirmed: the governing role of the families of close packed (crystallographic) planes, the independence of ordering of different types of atoms, the tendency of sulfur atoms to mirror plane symmetry, and the trend to cluster formation in the development of crystal structures, as exemplified by [As₄S₁₂]¹²⁻, [(Cs,Tl)S₁₂]²³⁻, [Tl₂S₁₂]²²⁻ atomic groups.     

L-cysteine as sustainable and effective sulfur source in the synthesis of diaryl sulfides and heteroarenethiols

L-cysteine, a natural and essential amino acid, was employed as novel sulfur source in the synthesis of symmetrical diaryl sulfides from a variety of aryl iodides in moderate to excellent yields. A tandem three steps’ reactions including C(sp²)-S bond formation, C(sp³)-S bond cleavage and another C(sp²)-S bond formation were proposed to be involved in this conversion. This protocol was featured by broad substrate scope and good functional group tolerance. In addition, heteroarenes including benzothiazoles and benzoxazoles were successfully converted into the corresponding heteroarenethiols using L-cysteine as C-H mercaptalization reagent.     

Unfairly forgotten member of the iodocarborane family: synthesis and structural characterization of 8-iodo-1,2-dicarba-closo-dodecaborane, its precursors, and derivatives

8-Iodo-1,2-dicarba-closo-dodecaborane (7) was prepared in three steps starting from decaborane-14 with 20% overall yield. In the presence of nucleophiles, compound 7 undergoes selective removal of the boron vertex in the position para to the iodine substituent to form the anionic nido-carborane 1-iodo-7,8-dicarba-nido-undecaborate. Capping of the corresponding dicarbollide dianion with BI(3) led to formation of the new carborane, 3,10-diiodo-1,2-dicarba-closo-dodecaborane (15). The same dicarbollide dianion reacts with cobalt and nickel acetylacetonates in anhydrous tetrahydrofuran to form the corresponding bis(dicarbollide) complexes with excellent yields. All compounds were characterized by multinuclear NMR and high-resolution mass spectroscopy. Structures of 2-iododecaborane (2), 8-iodo-1,2-dicarba-closo-dodecaborane (7), 1-ethoxycarbonyl-8-iodo-1,2-dicarba-closo-dodecaborane (10), cesium 1-iodo-7,8-dicarba-nido-undecaborate (13), 3,10-diiodo-1,2-dicarba-closo-dodecaborane (15), and cesium 3,3'-commo-(10-iodo-1,2-dicarba-3-cobalta-closo-dodecaborane)-(10'-iodo-1',2'-dicarba-3'-cobalta-closo-dodecaborane) (16) were established by X-ray analysis of single crystals.     

Acetylenic chemistry. Part 17 Acetylenic amides as precursors for the synthesis of 3-propynylquinazolinones

Cyclocondensation of acetylenic amides with triethylorthoformate and triethylorthoacetate in boiling glacial acetic acid under nitrogen gave 3-propynylquinazolinones. 2-Ethoxy-2-methyl-3[1,1-dimethylpropynyl]quinazolin-4(1H,3H)-one ( 3b ) and 2-ethoxy-2-methyl-3-[1-cyclohexylpropynyl]quinazolin-4(1H,3H)-one ( 3c ) in refluxing ethanolic sodium hydroxide afforded the corresponding oxazoloquinazolinones.     

2,6-Diazasemibullvalenes: synthesis, structural characterization, reaction chemistry, and theoretical analysis

A series of 2,6-diazasemibullvalenes (NSBVs) were synthesized and isolated from the reaction of 1,4-dilithio-1,3-dienes with nitriles via oxidant-induced C-N bond formation. For the first time, the activation barrier and an X-ray crystal structure of a substituted 2,6-diazasemibullvalene were determined. All NSBVs show extremely rapid aza-Cope rearrangement in solution, but the rapid aza-Cope rearrangement is "frozen" in the solid state, as shown by solid-state NMR measurements and X-ray single-crystal structural analysis. Insertion of unsaturated compounds or a low-valent metal center into the NSBV C-N bond gave diverse and interesting ring-expansion products. Theoretical analysis showed that the localized structure is predominant and that the homoaromatic delocalized structure exists as a minor component in the equilibrium.     

Atropisomeric lactam chemistry: catalytic enantioselective synthesis, application to asymmetric enolate chemistry and synthesis of key intermediates for NET inhibitors

In the presence of (R)-SEGPHOS-Pd(OAc)₂ catalyst, the intramolecular N-arylation of ortho-tert-butyl-NH-anilides possessing an iodophenyl group proceeded in a highly enantioselective manner (89-98% ee) to give optically active atropisomeric lactams having an N-C chiral axis. MPLC purification of the enantio-enriched lactam products using an achiral silica gel column led to a further increase in the enantiomeric purity (>99% ee). The reaction of the lithium enolate prepared from the optically active atropisomeric lactam with various alkyl halides gave α-substituted and α,α-disubstituted lactam products with high diastereoselectivity. α-Alkylated lactam derivatives were efficiently converted to key intermediates for the synthesis of an NET inhibitor.     

The synthesis of unusual isocoumarin derivatives: the chemistry of homophthalic acid

Homophthalic acid was reacted with thionyl chloride/DMF and ethyl chloroformate/NEt₃ in the presence and absence of NaN₃. In all cases completely different isocoumarin derivatives were obtained. These unusual isocoumarin derivatives were characterized and their mechanism of formation is discussed.     

Palladium(II)-selenoether complexes as new single source precursors: first synthesis of Pd4Se and Pd7Se4 nanoparticles

Pd(4)Se and Pd(7)Se(4) nanoparticles (size 38-104 nm), protected by TOP, have been obtained for the first time using Pd(II) ligated with selenated primary and secondary amines (see 1 and 2) as single source precursors respectively. TEM, SEM, powder XRD and photoluminescence have been used to characterize them. 1 and 2 are also the first Pd(II)-selenoether complexes used for the synthesis of nanoparticles containing palladium and selenium.     

Functionalized derivatives of 1,4-dimethylnaphthalene as precursors for biomedical applications: synthesis, structures, spectroscopy and photochemical activation in the presence of dioxygen

Decomposition of endoperoxide containing molecules is an attractive approach for the delayed release of singlet oxygen under mild reaction conditions. Here we describe a new method for the adaptation of the corresponding decay times by controlling the supramolecular functional structure of the surrounding matrix in the immediate vicinity of embedded singlet oxygen precursors. Thus, a significant prolongation of the lifetime of the endoperoxide species is possible by raising the energy barrier of the thermal (1)O(2)-releasing step via a restriction of the free volume of the applied carrier material. Enabling such a prolonged decomposition period is crucial for potential biomedical applications of endoperoxide containing molecules, since sufficient time for appropriate cell uptake and transport to the desired target region must be available under physiological conditions before the tissue damaging-power of the reactive oxygen species formed is completely exhausted. Two novel polyaromatic systems for the intermediate storage and transport of endoperoxides and the controlled release of singlet oxygen in the context of anticancer and antibiotic activity have been prepared and characterized. These compounds are based on functionalized derivatives of the 1,4-dimethylnaphthalene family which are readily forming metastable endoperoxide species in the presence of dioxygen, a photosensitizer molecule such as methylene blue and visible light. In contrast to previously known systems of similar photoreactivity, the endoperoxide carrying molecules have been designed with optimized molecular properties in terms of potential chemotherapeutic applications. These include modifications of polarity to improve their incorporation into various biocompatible carrier materials, the introduction of hydrogen bonding motifs to additionally influence the endoperoxide decay kinetics, and the synthesis of bifunctional derivatives to enable synergistic effects of multiple singlet oxygen binding sites with an enhanced local concentration of reactive species. With these compounds, a promising degree of endoperoxide stability adjustment within the carrier matrix has been achieved (polymer films or nanoparticles), which now opens the stage for appropriate targeting of the corresponding pro-drugs into live cells. First results on cytocidal and cytostatic properties of these compounds embedded in ethylcellulose nanoparticles are presented. Furthermore, an efficient low-cost method for the photochemical production of reactive endoperoxides based on high-power 660 nm LED excitation at room temperature and ambient conditions in ethanol solution is reported.     

Synthesis of hexadecylamine capped CdS nanoparticles using heterocyclic cadmium dithiocarbamates as single source precursors

Heterocyclic cadmium dithiocarbamates, [Cd(S₂CNC₅H₁₀)₂] and [Cd(S₂CNC₉H₁₀)₂] were synthesized. The complexes were thermolysed in hexadecylamine (HDA) to give HDA capped CdS nanoparticles. A combination of close to spherical, rod, bipods and tripods was obtained by varying the reaction parameters such as precursor concentration and temperature. The optical properties and X-ray diffraction studies of the particles are also reported.     

Magnesium oxide nanotubes: synthesis,characterization and application as efficient recyclable catalyst for pyrazolyl 1,4-dihydropyridine derivatives

Magnesium oxide nanotubes were prepared by electrospinning technique. The nanocatalysts have been characterized by various sophisticated techniques, including XRD, SEM, and TEM. The activities of these NT catalysts are promoting pyrazolyl 1,4-dihydropyridine syntheses have been extensively investigated. Various advantages associated with these protocols simple workup procedure, short reaction times, high yields and reusability of the catalyst.     

Synthesis and characterization of CuInS2 single source precursors for chemical vapor deposition

A family of single source precursors, for the spray chemical vapor deposition (CVD) of chalcopyrite thin films (CuInS₂), has been synthesized in good yields (ca. 65%). Newly synthesized compounds include [{L}₂Cu(SR)₂In(SR)₂], (R=alkyl, aryl; L=neutral donor ligand). The use of the single source precursors provides an attractive alternative over conventionally used multi-source precursors, which are often toxic, air sensitive and pyrophoric. However, it is desirable that these thin films be processed on flexible polymer substrates such as Kapton^TM. Therefore, milder deposition temperatures are needed to maintain the structural integrity of the underlying polymer substrates. By selective manipulation of the steric and electronic properties of the precursor, milder processing temperatures may be employed, while mainting the desired stoichiometry of the deposited films. Elucidation of the structures have been confirmed by the use of NMR. Thermal analytical techniques, differential scanning calorimetry (DSC) and thermogravimetric analysis (TG), have been employed to determine thermal profiles of each candidate compound. This revised version was published online in August 2006 with corrections to the Cover Date.     

The methyl group as a source of structural diversity in heterocyclic chemistry: side chain functionalization of picolines and related heterocycles

The reaction of 2-picoline at the methyl group with NDA and KDA followed by dimethyldisulfide trapping furnished, respectively, dithioacetals and trithioortho esters with high selectivity. The method was successfully applied to other methyl-substituted pyridines, quinolines, and pyrazines. Dithioketals were prepared by a one-pot procedure involving the reaction of metalated 2-picoline with 2 equiv of dimethyldisulfide followed by in situ trapping with a second electrophile. All of the generated thio-substituted compounds were efficiently transformed in presence of mercury salts or under oxidizing conditions to other functional groups comprising aldehydes, ketones, ketals, thiol esters, orthoesters, and esters.     

New triorganotin (IV) derivatives of dipeptides as models for metal-protein interactions: synthesis, structural characterization and biological studies

New non-electrolytic triorganotin(IV) derivatives of dipeptides with general formulae R3Sn(HL), where R = Ph and HL = monoanion of glycylisoleucine (H2L-1), valylvaline (H2L-2), alanylvaline (H2L-3), leucylalanine (H2L-4), leucylleucine (H2L-5); R = n-Bu and HL = monoanion of glycylisoleucine (H2L-1) and leucylalanine (H2L-4); and R = Me and HL = monoanion of leucylalanine (H2L-4) have been synthesized and characterized on the basis of infrared, multinuclear 1H, 13C and 119Sn NMR and 119Sn M?ssbauer spectroscopic studies. These investigations suggest that all the ligands in R3Sn(HL) act as monoanionic bidentates coordinating through the COO- and NH2 groups. The 119Sn M?ssbauer studies, together with the NMR data, indicate that, for these polymeric derivatives, the polyhedron around tin in R3Sn(HL) is a trigonal-bipyramid with the three organic groups in the equatorial positions, while the axial positions are occupied by a carboxylic oxygen and the amino nitrogen atom from the adjacent molecule. The anti-inflammatory and cardiovascular activities and toxicity of all these compounds have been determined. Four of the complexes have also been screened against some of the chosen bacterial and fungal strains. The Ph3Sn(IV) compounds exhibit better anti-inflammatory and cardiovascular activities in comparison to the Me3Sn(IV) and n-Bu3Sn(IV) analogues. n-Bu3Sn(Gly-Ile) and Ph3Sn(Ala-Val) exhibit good antibacterial activity against all the chosen strains.     

New P-stereogenic triaminophosphines and their derivatives: synthesis,structure, conformational study,and application as chiral ligands

The synthesis, structural, and conformational studies of new P-chiral triaminophosphines, which feature an indolidine and a 1,2,3,4-tetrahydroquinolidine pattern, respectively, are reported. These compounds can feature very different 3D-structures, although they both could be seen a priori as close derivatives of the previously reported 3-phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]octane. The consequences for the use of such compounds and their derivatives in asymmetric metal-catalysis are discussed on the basis of preliminary results in asymmetric cobalt-catalyzed [6+2] cycloaddition.     

A convenient synthesis of methylindium(III) dithiolate complexes—precursors for indium sulfides

Methylindium(III) dithiolate complexes of the general formulae [Me₂In(S^∩S)] ( 1 ) and [MeIn(S^∩S)₂] ( 2 ) [S^∩S = (EtO)₂PS₂^?, (PrⁱO)₂PS₂^?, Et₂NCS₂^?, , O(CH₂CH₂)₂NCS₂^?, EtOCS₂^? and PrⁱOCS₂^?] have been isolated conveniently by the reaction of Me₃In·OEt₂ with In(S^∩S)₃ ( 3 ) in an appropriate stoichiometry. Both 1 and 2 have been characterized by indium analysis, IR, NMR (¹H, ¹³C{¹H} and ³¹P{H}) and mass spectral data. NMR data of 3 are also included for comparison. The Me–In and S^∩S resonances are sensitive to the number of methyl groups attached to indium metal. The mass spectral data indicate that these complexes are monomeric in nature. The thermal behavior of a few complexes has been investigated. The xanthate and dithiocarbamate complexes on pyrolysis under dynamic vacuum or flowing nitrogen atmosphere gave either In₂S₃ or a mixture of InS, In₂S₃ and In₆S₇, which were characterized using EDAX and powder XRD. Copyright © 2005 John Wiley & Sons, Ltd.     

The application of nanostructured transition metal sulfides as anodes for lithium ion batteries

With wide application of electric vehicles and large-scale in energy storage systems, the requirement of secondary batteries with higher power density and better safety gets urgent. Owing to the merits of high theoretical capacity, relatively low cost and suitable discharge voltage, much attention has been paid to the transition metal sulfides. Recently, a large amount of research papers have reported about the application of transition metal sulfides in lithium ion batteries. However, the practical application of transition metal sulfides is still impeded by their fast capacity fading and poor rate performance. More well-focused researches should be operated towards the commercialization of transition metal sulfides in lithium ion batteries. In this review, recent development of using transition metal sulfides such as copper sulfides,molybdenum sulfides, cobalt sulfides, and iron sulfides as electrode materials for lithium ion batteries is presented. In addition, the electrochemical reaction mechanisms and synthetic strategy of transition metal sulfides are briefly summarized. The critical issues, challenges, and perspectives providing a further understanding of the associated electrochemical processes are also discussed.     

High structural control in metal-mediated synthesis of new functionalized diphosphines using diphosphinoketenimines as precursors

The diphosphinoketenimine ligand in the neutral complexes fac-[MnI(CO)(3){(PPh(2))(2)C=C=NR}] (1 a: R = Ph; 1 b: R = p-tolyl) undergoes nucleophilic attack by MeLi and nBuMgCl yielding, after hydrolysis, the diphosphinoenamine-containing complexes fac-[MnI(CO)(3){(PPh(2))(2)C=C(R')NHR}] (3 a,b: R' = Me; 4 a,b: R' = nBu). Complex 1 a reacts under the same conditions with H(2)C=C=CHMgBr to afford fac-[MnI(CO)(3){(PPh(2))(2)C=C(CH(2)CC[triple chemical bond]CH)NHR}] (5 a), which contains a terminal alkyne group on the alpha-carbon atom of the diphosphinoenamine ligand. The cationic complexes fac-[Mn(CO)(4){(PPh(2))(2)C=C=NR}](+) (6) react with H(2)C=C=CHMgBr to afford diphosphinomethanide derivatives bearing three different types of functional groups, depending upon the substituent on the nitrogen atom of the ketenimine: cumulene in fac-[Mn(CO)(4){(PPh(2))(2)C--C(CH=C=CH(2))=N-xylyl}] (7 d), internal alkyne in fac-[Mn(CO)(4){(PPh(2))(2)C--C(C[triple chemical bond]CCH(3))=NtBu}] (8), and quinoline in 9 (R = Ph), whose formation implies an unusual cyclization process. Protonation of 7 d, 8, and 9 with HBF(4) occurs at the nitrogen atom to give the cationic derivatives 10 d, 11, and 12, respectively, which contain the corresponding functionalized diphosphine ligands. Irradiation of 3 a,b and 4 a,b with Vis/UV light makes it possible to isolate the free ligands (PPh(2))(2)C=C(R')NHR (13 a,b and 14 a,b), completing the metal-assisted synthesis of these novel functionalized diphosphines. Irradiation of 12 with Vis/UV light generates free phosphinoquinoline ligand 15, which readily affords a complex 16 containing 15 as a P,N-chelating ligand when treated with [PdCl(2)(NCMe)(2)], thus demonstrating its coordination capability.