Showing papers on "Reactivity (chemistry) published in 2011"
TL;DR: Hydrogenolysis of lignin model compounds highlights the potential of this approach for the conversion of refractory aryl ether biopolymers to hydrocarbons.
Abstract: Selective hydrogenolysis of the aromatic carbon-oxygen (C-O) bonds in aryl ethers is an unsolved synthetic problem important for the generation of fuels and chemical feedstocks from biomass and for the liquefaction of coal. Currently, the hydrogenolysis of aromatic C-O bonds requires heterogeneous catalysts that operate at high temperature and pressure and lead to a mixture of products from competing hydrogenolysis of aliphatic C-O bonds and hydrogenation of the arene. Here, we report hydrogenolyses of aromatic C-O bonds in alkyl aryl and diaryl ethers that form exclusively arenes and alcohols. This process is catalyzed by a soluble nickel carbene complex under just 1 bar of hydrogen at temperatures of 80 to 120°C; the relative reactivity of ether substrates scale as Ar-OAr>>Ar-OMe>ArCH2-OMe (Ar, Aryl; Me, Methyl). Hydrogenolysis of lignin model compounds highlights the potential of this approach for the conversion of refractory aryl ether biopolymers to hydrocarbons.
684 citations
TL;DR: The chemistry described here, combining fundamental organometallic, catalytic, and organic methodology, remains rich in opportunities, especially considering that only a handful of gold(I) architectures has been studied.
Abstract: Gold has emerged as a powerful synthetic tool in the chemist’s arsenal. From the early use of inorganic salts such as AuCl and AuCl3 as catalysts, the field has evolved to explore ligands that fine-tune reactivity, stability, and, more recently, selectivity in gold-mediated processes. Substrates generally contain alkenes or alkynes, and they usually involve straightforward protocols in air with solvents that can oftentimes be of technical grade. The actual catalytic species is the putative cationic gold(I) complex [Au(L)]+ (where L is a phosphorus-based species or N-heterocyclic carbene, NHC). The early gold systems bearing phosphine and phosphite ligands provided important transformations and served as useful mechanistic probes. More recently, the use of NHCs as ligands for gold has rapidly gained in popularity. These two-electron donor ligands combine strong σ-donating properties with a steric profile that allows for both stabilization of the metal center and enhancement of its catalytic activity. As a ...
550 citations
TL;DR: The copper species is proposed to catalytically activate the hypervalent iodine(III) oxidants to give a more diverse range of products in good to excellent yields.
Abstract: New synthetic procedures for intramolecular oxidative C-N bond formation have been developed for the preparation of carbazoles starting from N-substituted amidobiphenyls under either Cu-catalyzed or metal-free conditions using hypervalent iodine(III) as an oxidant. Whereas iodobenzene diacetate or bis(trifluoroacetoxy)iodobenzene alone undergoes the reaction to provide carbazole products in moderate to low yields, combined use of copper(II) triflate and the iodine(III) species significantly improves the reaction efficiency, giving a more diverse range of products in good to excellent yields. On the basis of mechanistic studies including kinetic profile, isotope effects, and radical inhibition experiments, the copper species is proposed to catalytically activate the hypervalent iodine(III) oxidants. The synthetic utility of the present approach was nicely demonstrated in a direct synthesis of indolo[3,2-b]carbazole utilizing a double C-N bond formation.
446 citations
TL;DR: The mechanistic insights from this work may be extended to provide a general description of a new class of bifunctional heterogeneous catalysts, based on the combination of a highly reducible metal with an oxophilic metal, for the selective C-O hydrogenolysis of biomass-derived feedstocks.
Abstract: A ReOx-promoted Rh/C catalyst is shown to be selective in the hydrogenolysis of secondary C–O bonds for a broad range of cyclic ethers and polyols, these being important classes of compounds in biomass-derived feedstocks. Experimentally observed reactivity trends, NH3 temperature-programmed desorption (TPD) profiles, and results from theoretical calculations based on density functional theory (DFT) are consistent with the hypothesis of a bifunctional catalyst that facilitates selective hydrogenolysis of C–O bonds by acid-catalyzed ring-opening and dehydration reactions coupled with metal-catalyzed hydrogenation. The presence of surface acid sites on 4 wt % Rh–ReOx/C (1:0.5) was confirmed by NH3 TPD, and the estimated acid site density and standard enthalpy of NH3 adsorption were 40 μmol g–1 and −100 kJ mol–1, respectively. Results from DFT calculations suggest that hydroxyl groups on rhenium atoms associated with rhodium are acidic, due to the strong binding of oxygen atoms by rhenium, and these groups ar...
444 citations
TL;DR: In this tutorial review the fundamental electronic and structural properties of squaramides are explored to rationalise the geometry, conformation, reactivity and biological activity.
Abstract: Squaramides are remarkable four-membered ring systems derived from squaric acid that are able to form up to four hydrogen bonds. A high affinity for hydrogen bonding is driven through a concomitant increase in aromaticity of the ring. This hydrogen bonding and aromatic switching, in combination with structural rigidity, have been exploited in many of the applications of squaramides. Substituted squaramides can be accessed via modular synthesis under relatively mild or aqueous conditions, making them ideal units for bioconjugation and supramolecular chemistry. In this tutorial review the fundamental electronic and structural properties of squaramides are explored to rationalise the geometry, conformation, reactivity and biological activity.
415 citations
TL;DR: This tutorial review provides an overview of gold-catalysed C-H functionalisation, looking at transformations which rely on the ability of gold to perform C- H activation, as well as those exploiting its potent π-acidity.
Abstract: The transition metal-catalysed direct functionalisation of C-H bonds is an increasingly viable alternative to the multi-step strategies traditionally adopted. The use of powerful and environmentally benign gold(I) and gold(III) catalysts in such transformations has highlighted their remarkable reactivity and led to a significant increase in their utilisation. This tutorial review provides an overview of gold-catalysed C-H functionalisation, looking at transformations which rely on the ability of gold to perform C-H activation, as well as those exploiting its potent π-acidity.
401 citations
TL;DR: The critical review describes the known dicopper systems mediating the aromatic hydroxylation of monophenolic substrates as structural and functional models of the type 3 copper enzyme tyrosinase, which catalyzes the ortho-hydroxylations of tyrosine to DOPA and the subsequent two-electron oxidation to dopaquinone.
Abstract: The critical review describes the known dicopper systems mediating the aromatic hydroxylation of monophenolic substrates. Such systems are of interest as structural and functional models of the type 3 copper enzyme tyrosinase, which catalyzes the ortho-hydroxylation of tyrosine to DOPA and the subsequent two-electron oxidation to dopaquinone. Small-molecule systems involving μ-η²:η² peroxo, bis-μ-oxo and trans-μ-1,2 peroxo dicopper cores are considered separately. These tyrosinase models are contrasted to copper–dioxygen systems inducing radical reactions, and the different mechanistic pathways are discussed. In addition to considering the stoichiometric conversion of phenolic substrates, the available catalytic systems are described. The second part of the review deals with tyrosinase. After an introduction on the occurrence and function of tyrosinases, several aspects of the chemical reactivity of this class of enzymes are described. The analogies between the small-molecule and the enzymatic system are considered, and the implications for the reaction pathway of tyrosinase are discussed (140 references).
373 citations
TL;DR: A palladium(II) catalyst system, incorporating an unconventional ortho-dimethylaminopyridine ligand, is reported, for the conversion of substituted cyclohexanones to the corresponding phenols, demonstrating a versatile and efficient strategy for the synthesis of substituted aromatic molecules with fundamentally different selectivity constraints from the numerous known synthetic methods.
Abstract: Aromatic molecules are key constituents of many pharmaceuticals, electronic materials, and commodity plastics. The utility of these molecules directly reflects the identity and pattern of substituents on the aromatic ring. Here, we report a palladium(II) catalyst system, incorporating an unconventional ortho-dimethylaminopyridine ligand, for the conversion of substituted cyclohexanones to the corresponding phenols. The reaction proceeds via successive dehydrogenation of two saturated carbon-carbon bonds of the six-membered ring and uses molecular oxygen as the hydrogen acceptor. This reactivity demonstrates a versatile and efficient strategy for the synthesis of substituted aromatic molecules with fundamentally different selectivity constraints from the numerous known synthetic methods that rely on substitution of a preexisting aromatic ring.
359 citations
TL;DR: The study reveals that Fe/FeS nanoparticles are a promising candidate for the efficient removal of pollutants.
Abstract: Multicomponent nanoparticles containing two or more different types of functionalities show unique physical and chemical properties, leading to significantly enhanced performance. In this study, we have developed a new one-pot method to prepare Fe/FeS nanoparticles using dithionite at room temperature. The FeS precipitates on the Fe surface are formed by the interaction between dissolved iron species and hydrogen sulfide, one of the decomposition products of dithionite in solution. The resulting Fe/FeS nanoparticles have high surface area, good electrical conductivity, and strong magnetic responsivity. In addition, the Fe/FeS shows a much higher reactivity toward contaminants than the pure Fe nanoparticles. The above synthesized nanoparticles are successfully applied for the rapid removal of trichloroethylene (TCE) from water. The study reveals that Fe/FeS nanoparticles are a promising candidate for the efficient removal of pollutants.
331 citations
TL;DR: In this article, the authors studied the geopolymerisation of mechanically activated fly ash at ambient (27 degrees C) and elevated (60 degrees C), by isothermal conduction calorimeter.
300 citations
TL;DR: In this paper, the mechanism of the hydrogenolysis of glycerol to 1,3-propanediol over Ir-ReOx/SiO2 catalyst was discussed.
Abstract: The mechanism of the hydrogenolysis of glycerol to 1,3-propanediol over Ir–ReOx/SiO2 catalyst was discussed. We investigated the catalytic performance, structure, reaction kinetics and reactivity trends of various substrates over the catalysts with different amount of Re. The conversion in the glycerol hydrogenolysis increased with increasing the amount of Re up to Re/Ir = 2, and the high selectivity to 1,3-propanediol (ca. 60%) was almost independent of the Re amount. The average size of Ir metal particle gradually decreased with increasing the amount of Re from XRD and TEM. Characterization results such as CO adsorption, TPR, XANES, EXAFS suggested that Ir metal surface was partially covered with ReOx cluster regardless of the Re amount. The reaction order on H2 pressure over Ir–ReOx/SiO2 (Re/Ir = 1) was one, suggesting that one active hydrogen species was produced from one hydrogen molecule. Low reaction order on glycerol concentration represented the strong interaction between glycerol and catalyst surface. This catalyst is also applicable to the selective hydrogenolysis of the C–O bond neighboring a –CH2OH group. These reaction trends and characterization results supported the direct reaction mechanism for the formation of 1,3-propanediol from glycerol via 2,3-dihydroxypropoxide species.
TL;DR: Reactivity results demonstrate that iron(iii)–hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes.
Abstract: The iron–oxygen species iron(III)-peroxo, iron(III)-hydroperoxo and iron(IV)-oxo are key intermediates often detected in the catalytic cycles of dioxygen activation by haem and non-haem iron enzymes. The high-resolution crystal structure of a mononuclear non-haem side-on iron(III)-peroxo complex has now been determined, and a series of chemical reactions in which the iron(III)-peroxo complex is cleanly converted to an iron(III)-hydroperoxo complex is described. All three of these iron species have been spectroscopically characterized, and relative reactivity studies demonstrate that iron(III)-hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes. This work shows how a series of biologically important iron–oxygen intermediates make use of a synthetic iron complex bearing a simple but versatile macrocyclic ligand. Oxygen-containing mononuclear iron species—iron(iii)–peroxo, iron(iii)–hydroperoxo and iron(iv)–oxo—are key intermediates in the catalytic activation of dioxygen by iron-containing metalloenzymes1,2,3,4,5,6,7. It has been difficult to generate synthetic analogues of these three active iron–oxygen species in identical host complexes, which is necessary to elucidate changes to the structure of the iron centre during catalysis and the factors that control their chemical reactivities with substrates. Here we report the high-resolution crystal structure of a mononuclear non-haem side-on iron(iii)–peroxo complex, [Fe(iii)(TMC)(OO)]+. We also report a series of chemical reactions in which this iron(iii)–peroxo complex is cleanly converted to the iron(iii)–hydroperoxo complex, [Fe(iii)(TMC)(OOH)]2+, via a short-lived intermediate on protonation. This iron(iii)–hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(iv)(TMC)(O)]2+, via homolytic O–O bond cleavage of the iron(iii)–hydroperoxo species. All three of these iron species—the three most biologically relevant iron–oxygen intermediates—have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(iii)–hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(iv)–oxo complex in C–H bond activation of alkylaromatics. These reactivity results demonstrate that iron(iii)–hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes.
TL;DR: In this article, the authors discuss how, for reactions and kinetics of bioinorganic species, particular pathways are also exchange-enhanced, that is, favored by an increase in the number of unpaired and spin-identical electrons on a metal centre.
Abstract: Principles based on overlaps and interactions between bonding and antibonding orbitals are known to control chemical reactivity. This Perspective discusses how, for reactions and kinetics of bioinorganic species, particular pathways are also exchange-enhanced — that is, favoured by an increase in the number of unpaired and spin-identical electrons on a metal centre.
TL;DR: It is proposed that the set of interactions is better described as a means of stabilizing the anionic transition state of the reaction, and the enhanced acidity of the critical cysteine is concurrent but not the cause of catalytic efficiency.
Abstract: Protein thiol reactivity generally involves the nucleophilic attack of the thiolate on an electrophile. A low pKa means higher availability of the thiolate at neutral pH but often a lower nucleophilicity. Protein structural factors contribute to increasing the reactivity of the thiol in very specific reactions, but these factors do not provide an indiscriminate augmentation in general reactivity. Notably, reduction of hydroperoxides by the catalytic cysteine of peroxiredoxins can achieve extraordinary reaction rates relative to free cysteine. The discussion of this catalytic efficiency has centered in the stabilization of the thiolate as a way to increase nucleophilicity. Such stabilization originates from electrostatic and polar interactions of the catalytic cysteine with the protein environment. We propose that the set of interactions is better described as a means of stabilizing the anionic transition state of the reaction. The enhanced acidity of the critical cysteine is concurrent but not the cause o...
TL;DR: This study pioneers the implementation of variable-temperature mass spectrometry to investigate reactive intermediates and the generation of a Fe(V)=O species within a synthetic non-haem complex at -40 °C and its reaction with an olefin.
Abstract: Oxo-transfer chemistry mediated by iron underpins many biological processes and today is emerging as synthetically very important for the catalytic oxidation of C-H and C=C moieties that are hard to activate conventionally. Despite the vast amount of research in this area, experimental characterization of the reactive species under catalytic conditions is very limited, although a Fe(V)=O moiety was postulated. Here we show, using variable-temperature mass spectrometry, the generation of a Fe(V)=O species within a synthetic non-haem complex at -40 °C and its reaction with an olefin. Also, with isotopic labelling we were able both to follow oxygen-atom transfer from H(2)O(2)/H(2)O through Fe(V)=O to the products and to probe the reactivity as a function of temperature. This study pioneers the implementation of variable-temperature mass spectrometry to investigate reactive intermediates.
TL;DR: Recent developments in the reactions of the multiple bonded and other open shell derivatives of the heavier main group elements with hydrogen, ammonia, olefins, or related molecules are summarized.
Abstract: We showed in 2005 that a digermyne, a main group compound with a digermanium core and aromatic substituents, reacted directly with hydrogen at 25 °C and 1 atm to give well-defined hydrogen addition products. This was the first report of a reaction of main group molecules with hydrogen under ambient conditions. Our group and a number of others have since shown that several classes of main group molecules, either alone or in combination, react directly (in some cases reversibly) with hydrogen under mild conditions. Moreover, this reactivity was not limited to hydrogen but also included direct reactions with other important small molecules, including ammonia, boranes, and unactivated olefins such as ethylene. These reactions were largely unanticipated because main group species were generally considered to be too unreactive to effect such transformations.In this Account, we summarize recent developments in the reactions of the multiple bonded and other open shell derivatives of the heavier main group element...
TL;DR: In this paper, it was shown that for all the essential bond forming and bond breaking reactions on metal surfaces, the reactivity of the metal surface correlates linearly with the reaction energy in a single universal relation.
Abstract: It is shown that for all the essential bond forming and bond breaking reactions on metal surfaces, the reactivity of the metal surface correlates linearly with the reaction energy in a single universal relation. Such correlations provide an easy way of establishing trends in reactivity among the different transition metals.
TL;DR: A detailed electronic structure analysis of alkane hydroxylation by an oxo-iron(IV) species on different spin-state potential energy surfaces is performed and shows that the lengthening of the Fe–oxo bond in ferryl reactants, which is the part of the reaction coordinate for H-atom abstraction, leads to the formation of oxyl- iron(III) species that then perform actual C–H bond activation.
Abstract: Oxo-iron(IV) species are implicated as key intermediates in the catalytic cycles of heme and nonheme oxygen activating iron enzymes that selectively functionalize aliphatic C–H bonds. Ferryl complexes can exist in either quintet or triplet ground states. Density functional theory calculations predict that the quintet oxo-iron(IV) species is more reactive toward C–H bond activation than its corresponding triplet partner, however; the available experimental data on model complexes suggests that both spin multiplicities display comparable reactivities. To clarify this ambiguity, a detailed electronic structure analysis of alkane hydroxylation by an oxo-iron(IV) species on different spin-state potential energy surfaces is performed. According to our results, the lengthening of the Fe–oxo bond in ferryl reactants, which is the part of the reaction coordinate for H-atom abstraction, leads to the formation of oxyl-iron(III) species that then perform actual C–H bond activation. The differential reactivity stems from the fact that the two spin states have different requirements for the optimal angle at which the substrate should approach the (FeO)2+ core because distinct electron acceptor orbitals are employed on the two surfaces. The H-atom abstraction on the quintet surface favors the “σ-pathway” that requires an essentially linear attack; by contrast a “π-channel” is operative on the triplet surface that leads to an ideal attack angle near 90°. However, the latter is not possible due to steric crowding; thus, the attenuated orbital interaction and the unavoidably increased Pauli repulsion result in the lower reactivity of the triplet oxo-iron(IV) complexes.
TL;DR: The extension of the frustrated Lewis pair (FLP) concept to the transition series with cationic zirconocene-phosphinoaryloxide complexes is demonstrated, and these transition metal FLPs are markedly more reactive than main group systems in many cases.
Abstract: The extension of the frustrated Lewis pair (FLP) concept to the transition series with cationic zirconocene–phosphinoaryloxide complexes is demonstrated. Such complexes mimic the reactivity of main group FLPs in reactions such as heterolytic hydrogen cleavage, CO2 activation, olefin and alkyne addition, and ring-opening of tetrahydrofuran. The interplay between sterics and electronics is shown to have an important role in determining the reactivity of these compounds with hydrogen in particular. The Zr–H species generated from the heterolytic activation of hydrogen is shown to undergo insertion reactions with both CO2 and CO. Crucially, these transition metal FLPs are markedly more reactive than main group systems in many cases, and in addition to the usual array of reactions they demonstrate unprecedented reactivity in the activation of small molecules. This includes SN2 and E2 reactions with alkyl chlorides and fluorides, enolate formation from acetone, and the cleavage of C–O bonds to facilitate SN2 ty...
TL;DR: In this paper, the solar thermochemical splitting of CO2 and H2O with ceria and Zr-doped ceria for CO and H 2 production is considered, and the two-step process is composed of the thermal reduction of the ceria-based compound followed by the oxidation of the nonstoichiometric ceria with CO2/H2O to generate CO/H 2, respectively.
Abstract: The solar thermochemical splitting of CO2 and H2O with ceria and Zr-doped ceria for CO and H2 production is considered. The two-step process is composed of the thermal reduction of the ceria-based compound followed by the oxidation of the nonstoichiometric ceria with CO2/H2O to generate CO/H2, respectively. As a reference, the reactivity of pure undoped ceria was first characterized during successive thermochemical cycles using a thermobalance. Then, Zr0.25Ce0.75O2 was synthesized using different soft chemical synthesis routes to evaluate the influence of the powder morphology on the reactivity during the reduction and the oxidation steps. The reduction yield of ceria was significantly improved by doping with Zr as well as the CO/H2 production yields, but the kinetic rates of the oxidation step for doped ceria were lower than for pure ceria. CO and H2 production of 241 and 432 μmol/g, respectively, have been measured. A kinetic analysis of the CO2-splitting step allowed one to estimate the activation ener...
TL;DR: The reactivity of hydrogen sulfide was compared to that of low-molecular-weight thiols such as cysteine and glutathione and probably cannot completely account for its protective effects.
TL;DR: It is proposed that C-H bond activation by the non-heme Mn(IV)-oxo complex does not occur via an oxygen-rebound mechanism.
Abstract: A mononuclear non-heme manganese(IV)-oxo complex has been synthesized and characterized using various spectroscopic methods. The Mn(IV)-oxo complex shows high reactivity in oxidation reactions, such as C-H bond activation, oxidations of olefins, alcohols, sulfides, and aromatic compounds, and N-dealkylation. In C-H bond activation, the Mn(IV)-oxo complex can activate C-H bonds as strong as those in cyclohexane. It is proposed that C-H bond activation by the non-heme Mn(IV)-oxo complex does not occur via an oxygen-rebound mechanism. The electrophilic character of the non-heme Mn(IV)-oxo complex is demonstrated by a large negative ρ value of -4.4 in the oxidation of para-substituted thioanisoles.
TL;DR: In this article, the authors described a simple approach to obtain a wide range of alcohol and/or ester functionalized renewable monomers using solvent and radical initiator-free addition of thiols to terpenes.
Abstract: Solvent and radical initiator-free addition of thiols to terpenes ((R)-(+)- and (S)-(−)-limonene and (−)-β-pinene) are described as a simple approach to obtain a wide range of alcohol and/or ester functionalized renewable monomers. (R)-(+)-Limonene (1) and (S)-(−)-limonene (2), presenting different reactivity at the endocyclic and exocyclic double bonds, have yielded the monoaddition or diaddition product by simple variation of the thiol feed ratio. In the same manner, (−)-β-pinene (3) derived alcohol and ester monomers have been prepared. The monomers thus obtained have been characterized, and their behavior in polycondensation has been studied. It has been found that long chain diesters or diols, which were synthesized from a castor oil derived platform chemical, are suitable comonomers and result in polycondensates with number-average molecular weights of up to 25 kDa. Thus, terpene/fatty acid-based polyesters were prepared, and their structure–thermal property relationships were studied.
TL;DR: A selection of recent achievements concerning the reaction mechanisms in the vanadium catalysed oxidation and bromination reactions with peroxides can be found in this paper, however, no clear-cut evidence of nucleophilic reactivity of vanadium peroxo complexes has been obtained.
TL;DR: The work has shown that the M-C(cage) bonds in transition metal-carboranyl complexes are generally inert toward electrophiles, and hence significantly different from traditional M-cage bonds, which can be ascribed to steric effects resulting from the carboranyl moiety.
Abstract: The construction and transformation of metal−carbon (M−C) bonds constitute the central themes of organometallic chemistry. Most of the work in this field has focused on traditional M−C bonds involving tetravalent carbon: relatively little attention has been paid to the chemistry of nontraditional metal−carbon (M−Ccage) bonds, such as carborane cages, in which the carbon is hypervalent. We therefore initiated a research program to study the chemistry of these nontraditional M−Ccage bonds, with a view toward developing synthetic methodologies for functional carborane derivatives. In this Account, we describe our results in constructing and elucidating the chemistry of transition metal−carboryne complexes.Our work has shown that the M−Ccage bonds in transition metal−carboranyl complexes are generally inert toward electrophiles, and hence significantly different from traditional M−C bonds. This lack of reactivity can be ascribed to steric effects resulting from the carboranyl moiety. To overcome this steric p...
TL;DR: A palladium-catalyzed carbon-carbon bond-forming reaction between aryl iodides and alkenes is reported, in contrast to traditional cross-coupling reactions, two new bonds are formed, and all of the atoms in the starting materials are incorporated into the product.
Abstract: We report a palladium-catalyzed carbon-carbon bond-forming reaction between aryl iodides and alkenes. In contrast to traditional cross-coupling reactions, two new bonds are formed, and all of the atoms in the starting materials are incorporated into the product. The use of a palladium catalyst with bulky phosphine ligands is found to be crucial for reactivity.
TL;DR: In this paper, a review of the activation, aggregation and degradation of white phosphorus by molecules containing reactive p-block centers has been presented, where the chemistry has been divided into a number of reaction types and possible mechanisms are used to aid in the understanding of these reactions.
TL;DR: Rh(III)-catalyzed ortho C-H activation/olefination of phenol carbamates provides a new approach for the synthesis of ortho-substituted phenols and enables efficient coupling with acrylates and styrenes.
TL;DR: A new palladium(II) catalyzed methodology for the direct synthesis of alkylidene isoindolinones from N-alkoxybenzamides is presented and both systems were found to tolerate a wide range of functionality.
TL;DR: It is reported that embedding the highly inert 1,2,3-triazole moiety within a poly(methyl acrylate) chain renders it susceptible to ultrasound-induced cycloreversion, as confirmed by comprehensive spectroscopic and chemical analyses.
Abstract: The specific targeting of covalent bonds in a local, anisotropic fashion using mechanical methods offers useful opportunities to direct chemical reactivity down otherwise prohibitive pathways. Here, we report that embedding the highly inert 1,2,3-triazole moiety (which is often prepared using the canonical "click" coupling of azides and alkynes) within a poly(methyl acrylate) chain renders it susceptible to ultrasound-induced cycloreversion, as confirmed by comprehensive spectroscopic and chemical analyses. Such reactivity offers the opportunity to develop triazoles as mechanically labile protecting groups or for use in readily accessible materials that respond to mechanical force.