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The fluorescence excitation spectra of jet-cooled benzocyclobutane have been recorded and together with its ultraviolet absorption spectra have been used to assign the vibrational frequencies for this molecule in its S1(π,π*) electronic excited state. Theoretical calculations at the CASSCF(6,6)/augcc- pVTZ level of theory were carried out to compute the structure of the molecule in its excited state. The calculated structure was compared to that of the molecule in its electronic ground state as well as to the structures of related molecules in their S0 and S1(π,π*) electronic states. In each case the decreased π bonding in the electronic excited states results in longer carbon-carbon bonds in the benzene ring. The skeletal vibrational frequencies in the electronic excited state were readily assigned and these were compared to the ground state and to the frequencies of five similarmolecules. The vibrational levels in both S0 and S1(π,π*) states were remarkably harmonic in contrast to the other bicyclic molecules. The decreases in the frequencies of the out-of-plane skeletal modes reflect the increased floppiness of these bicyclic molecules in their S1(π,π*) excited state. [ABSTRACT FROM AUTHOR]

This research project introduced a novel transition metal‐free C−C coupling reaction that is believed to be a new revolution in Suzuki type reactions. Carbon‐carbon bond formation can be promoted by a mixture of 2‐mercaptoethanol/KOH/DMSO without the aid of any transition metals. It has been suggested that this reaction proceeds through radical species, hence the electron transfer route is suggested for the operation during the oxidation of 2‐mercaptoethanol in DMSO. [ABSTRACT FROM AUTHOR]

This research demonstrates an economical and efficient reduction of carbon foot print. Tapioca powder as a source of organic carbon was utilized in the synthesis of carbon dots through optimization of the synthesis parameters such as temperature, dosage and time. Photoluminescent quantum yield (PLQY) was obtained under the visible region of 340 nm at 34.9%, which was achieved without dopants such as sulfur and nitrogen that are popularly used to increase the value of photoluminescence. The characterization of carbon dots such as FTIR and HrTem, were carried out for the analysis of functional groups, particle sizes (1‐5 nm) and shapes (quasi‐spherical). The high carbon‐carbon bonds and oxygen groups detected in FTIR analysis validates the basis of fluorescence of carbon dots and also presence of hydroxyl (OH), carboxylic acids (COO), and other vital functional groups (C=O, C−O‐C, C−H). These characteristics makes tapioca based carbon dots suitable for application in the fields of environmental studies including sensitive detection and absorbance of pollutants in water and bio imaging in health sciences. [ABSTRACT FROM AUTHOR]

Converting biomass into valuable products has great benefits in terms of both economic and environmental considerations, and has attracted considerable attention in recent years. Rice husk biomass was initially utilized to produce bulk materials for conventional applications while a variety of advanced nanostructures (NSs) have been fabricated over the past few years. In addition to their low cost and environmental friendliness, RH‐derived NSs (RH‐NSs) exhibit versatile properties, which are promising for broad applications in various fields. In this Review, we summarize the latest research on RH‐NSs, covering their design, fabrication, properties, and applications in the modern energy field. Based on the unique structure and components of RHs, a series of carbon/silicon‐based novel NSs with outstanding performances have been exploited, which are difficult to be synthesized using conventional chemical reagents. We also discuss perspective uses of RH‐NSs on the basis of the current research progress. Made from rice: Owing to its unique three‐dimensional net structure and chemical composition, rice husk biomass can be used to prepare versatile carbon‐ and silicon‐based nanostructures, as well as nanocomposites. Nanostructures derived from rice husks exhibit excellent optical, electrical, and electrochemical properties, with broad application prospects in lithium ion batteries, supercapacitors, solar cells, and triboelectric nanogenerators. [ABSTRACT FROM AUTHOR]

Abstract: By using Pd0/Mandyphos, we achieved a three‐component aminoarylation of alkynes to generate enamines, which are then hydrolyzed to either α‐arylphenones or α,α‐diarylketones. This Pd‐catalyzed method overcomes established known pathways to enable the use of amines as traceless directing groups for C−C bond formation. [ABSTRACT FROM AUTHOR]

On the basis of the strategy of iminyl radical-mediated C–C bond cleavage, a visible light photocatalytic radical addition/cyclization cascade is described, providing an efficient and regioselective access to cyanoalkylated 1,2,3,4-tetrahydrophenanthrenes. [ABSTRACT FROM AUTHOR]

We investigate the effect of covalently modified graphitic surfaces on the formation of single-layer covalent organic frameworks (sCOFs) at the solid–liquid interface. The impact of different densities of grafted aryl species was tested on the on-surface synthesis of three distinct imine-based 2D sCOFs. The grafted aryl species that act as defects provide steric barriers to the progress of the Schiff-base reaction, and can be locally removed to start the 2D polymer healing process. This unique strategy provides a general approach to study in situ this dynamic covalent on-surface chemistry. [ABSTRACT FROM AUTHOR]

Abstract: Die Photokatalyse mit sichtbarem Licht hat sich im letzten Jahrzehnt zu einer breit angewandten Methode in der organischen Synthese entwickelt. Für viele wichtige Reaktionen, wie Kreuzkupplungen, α‐Amino‐Funktionalisierungen, Cycloadditionen, ATRA‐Reaktionen oder Fluorierungen, wurden photokatalytische Varianten berichtet. Um Chemiker bei der Auswahl photokatalytischer Methoden für ihre Synthesen zu unterstützen, vergleichen wir in diesem Aufsatz klassische und photokatalytische Verfahren für ausgewählte Reaktionsklassen und zeigen deren Vorteile und Grenzen auf. In vielen Fällen verlaufen die photokatalytischen Reaktionen unter milderen Reaktionsbedingungen, typischerweise bei Raumtemperatur, und stöchiometrische Reagenzien werden durch einfache Oxidanzien oder Reduktionsmittel wie Luft, Sauerstoff oder Amine ersetzt. Beeinflusst die Photokatalyse mit sichtbarem Licht die organische Synthese? Die Aussicht, Elektronen zu Substraten und Zwischenprodukten hin‐ und herzuschieben oder Energie selektiv durch einen sichtbares Licht absorbierenden Photokatalysatoren zu übertragen, verspricht die aktuellen Verfahren in der Radikalchemie zu verbessern und neue Wege durch den Zugang zu reaktiven, bisher unbekannten Spezies zu erschließen, insbesondere durch das Zusammenspiel von Photokatalyse mit der Organo‐ oder Metallkatalyse. [ABSTRACT FROM AUTHOR]

A Lewis acid-catalyzed [3 + 3] cycloaddition reaction of donor‒acceptor aziridines with N,N -dialkyl-3-vinylanilines has been developed for the stereoselective synthesis of tetrahydroisoquinolines (THIQs). The reaction performed using Gd(OTf) 3 as the Lewis acid catalyst was tolerant to various N -tosylaziridine and N,N -dialkyl-3-vinylaniline substrates and provided access to highly functionalized THIQs in typically high yields with moderate-to-excellent diastereoselectivities. [ABSTRACT FROM AUTHOR]

Abstract: A “totally catalytic” nickel(0)‐mediated method for base‐free direct alkylation of allyl alcohols and allyl amines is reported. The reaction is selective for monoallylation, uses an inexpensive NiII precatalyst system, and requires no activating reagents to be present. [ABSTRACT FROM AUTHOR]

Molecular conversion reaction system containing a dye and a biocatalyst catalyzing a reaction of a carbon–carbon bond formation from CO 2 as a feedstock were constructed. For example, NADP-malic enzyme (ME, EC1.1.1.40) catalyzes the reaction of introducing CO 2 as a carboxy group to pyruvate (C3 compound) to form malate (C4 compound) via oxaloacetate in the presence of natural co-enzyme NADPH. In a recent study, visible light-induced oxaloacetate production from pyruvate and CO 2 with the system consisting an electron donor, a photosensitizer, diphenylviologen (PV 2+ ) derivative as an electron mediator and ME was reported. However, the visible light-induced reduction properties of PV 2+ with water-soluble Zn porphyrin have not been clarified. In this study, chemical and photo-redox properties of PV 2+ were studied. In addition, to produce malate, CO 2 saturated reaction solution containing triethanolamine, tetraphenylporphine tetrasulfonate (H 2 TPPS), pyruvate, PV 2+ and ME in the presence of Mg 2+ , co-factor for ME was irradiated with visible-light, the oxaloacetate and malate were produced. [ABSTRACT FROM AUTHOR]

Walnut shell-stabilized copper nanoparticles (CuNP/WS) were successfully prepared by a simple reaction of copper sulfate and Sodium borohydride. Formation of copper nanoparticles in this bio-nanocomposite was observed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscope (EDX). CuNP/WS was found to be an efficient, inexpensive, easy to prepare, green and reusable catalyst in the reduction of aromatic nitro and nitrile compounds to their corresponding amines with NaBH4 at 35 °C in aqueous medium. We continued our studies on the application of this nanocomposite in the classic Ullman reaction to synthesize biaryl. This method has the advantages of high yields, elimination of expensive stabilizer and homogeneous catalysts, simple methodology and easy work up. The catalyst can be recovered from the reaction mixture and reused several times without any significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

This report describes a three-component, Nicatalyzed reductive coupling that enables the convergent synthesis of tertiary benzhydryl amines, which are challenging to access by traditional reductive amination methodologies. The reaction makes use of iminium ions generated in situ from the condensation of secondary N-trimethylsilyl amines with benzaldehydes, and these species undergo reaction with several distinct classes of organic electrophiles. The synthetic value of this process is demonstrated by a single-step synthesis of antimigraine drug flunarizine (Sibelium) and high yielding derivatization of paroxetine (Paxil) and metoprolol (Lopressor). Mechanistic investigations support a sequential oxidative addition mechanism rather than a pathway proceeding via α-amino radical formation. Accordingly, application of catalytic conditions to an intramolecular reductive coupling is demonstrated for the synthesis of endo- and exocyclic benzhydryl amines. [ABSTRACT FROM AUTHOR]

Highly fluorescent N and S co-doped carbon dots (CDs) were synthesized in one pot using caffeine as a raw material via a facile, green and cost-effective solid-state method. It is found that when caffeine and a mixture of caffeine and urea were heated, the CDs were not produced. However, when a mixture of caffeine and ammonium persulfate was heated, the CDs were fabricated successfully and exhibited the blue fluorescence with a quantum yield of 38%. In addition, the formation of CDs was enhanced with excellent optical properties when urea was added to the mixture of caffeine and ammonium persulfate. Without further chemical modification, the CDs emitted bright blue fluorescence with a high quantum yield as high as 69% due to the enhancement effect of N and S co-dopants on the surface of the CDs. Owing to the strong blue fluorescence, the CDs fabricated in this study could be used effectively as a fluorescence probe for Ag + ions that exhibited high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

Transition-metal mediated C-H functionalization has emerged as a powerful method in the chemistry relevant to the synthesis of pharmaceuticals, agrochemicals, and advanced materials. Because organic molecules typically contain multiple types of C-H bonds, selective C-H functionalization is a major ongoing challenge. C-H activation of heteroatom-containing organics has often been approached via the use of the directing effect, whereby the coordination to the basic heteroatom directs the reactive metal center to a specific C-H bond. We now report a different approach where the nitrogen donor in pyridine derivatives coordinates to an ancillary Lewis acidic boryl ligand directly attached to the metal (iridium) center, as opposed to the metal itself. This topology directs the iridium center to activate a different C-H bond than in the cases of directing donor coordination to the metal. Using this strategy, we demonstrate ortho-regiospecific C-H activation of pyridines and an example of the subsequent functionalization via C-C bond formation. [ABSTRACT FROM AUTHOR]

The enantioselective total synthesis of (-)-hodgkinsine, (-)-calycosidine, (-)-hodgkinsine B, (-)-quadrigemine C, and (-)-psycholeine through a diazene-directed assembly of cyclotryptamine fragments is described. Our synthetic strategy enables multiple and directed assembly of intact cyclotryptamine subunits for convergent synthesis of highly complex bis- and tris-diazene intermediates. Photoextrusion of dinitrogen from these intermediates enables completely stereoselective formation of all C3a-C3a′ and C3a-C7′ carbon-carbon bonds and all the associated quaternary stereogenic centers. In a representative example, photoextrusion of three dinitrogen molecules from an advanced intermediate in a single-step led to completely controlled introduction of four quaternary stereogenic centers and guided the assembly of four cyclotryptamine monomers en route to (-)-quadrigemine C. The synthesis of these complex diazenes was made possible through a new methodology for synthesis of aryl-alkyl diazenes using electronically attenuated hydrazine-nucleophiles for a silver-promoted addition to C3a-bromocyclotryptamines. The application of Rh- and Ir-catalyzed C-H amination reactions in complex settings were used to gain rapid access to C3a- and C7-functionalized cyclotryptamine monomers, respectively, used for diazene synthesis. This convergent and modular assembly of intact cyclotryptamines offers the first solution to access these alkaloids through completely stereoselective union of monomers at challenging linkages and the associated quaternary stereocenters as illustrated in our synthesis of five members of the oligocyclotryptamine family of alkaloids. [ABSTRACT FROM AUTHOR]

Base-promoted insertion reactions of alkynes into the C-C σ-bonds of α-cyano ketones were established to construct highly functionalized conjugated olefins or chromone derivatives via transition metal-free tandem reactions. These reactions are initialized through the nucleophilic attack of α-cyano ketones to alkynones followed by intramolecular nucleophilic addition/ring-opening to furnish the cyano-containing alkenes. In the cases of alkynones bearing an ortho-halide-substituted aryl ring, a further C-O bond coupling reaction occurs to afford chromone derivatives in good to high yields. Various alkynones bearing alkyl or aryl substituents were compatible in the reaction. This reaction has the potential to become a general synthetic protocol for the preparation of cyano-substituted olefins and chromones due to the abundance of easily accessible starting materials possessing diverse substituent groups. [ABSTRACT FROM AUTHOR]

A silver-catalyzed tandem carbon-carbon triple bond hydroazidation, radical addition, and cyclization of biphenyl acetylene is described under mild conditions, leading to the formation of 6-methyl sulfonylated phenanthridines in good yields. In this novel cascade reaction, most of the atoms are incorporated into the product without cleavage of the C·C bond. Mechanistic studies suggest the reaction should proceed through an iminyl radical reactive intermediate. [ABSTRACT FROM AUTHOR]

Incorporation of CO2 into heterocyclic compounds (i.e., 2-oxazolidinones) under mild conditions, especially at atmospheric pressure still remains challenging. The mononuclear ZnII complex ZnCl2(TBD)2, where TBD=1,5,7-triazabicyclo[4.4.0]dec-5-ene, in this study was demonstrated as a robust catalyst for the carboxylative cyclization of propargylic amines with CO2 to exclusively afford various 2-oxazolidinones in excellent yields. Notably, the ZnII catalytic species is readily generated in situ from ZnCl2 and TBD without pre-preparation and further isolation. Such a CO2 fixation protocol could proceed smoothly under atmospheric pressure at mild temperature in an atom economic and environmentally benign manner. 13C NMR and control experiments were performed to explore the possible interaction between ZnII and the carbon-carbon triple bond of propargylic amine. The dual catalytic role of the Zn catalyst to enhance O-nucleophilicity of the carbamate anion intermediate and activate the carbon-carbon triple bond is proposed based on mechanistic investigations. [ABSTRACT FROM AUTHOR]

Metal-metal bonds play a vital role in stabilizing key intermediates in bond-formation reactions. We report that binuclear benzo[ h]quinoline-ligated NiII complexes, upon oxidation, undergo reductive elimination to form carbon-halogen bonds. A mixed-valent Ni(2.5+)-Ni(2.5+) intermediate is isolated. Further oxidation to NiIII, however, is required to trigger reductive elimination. The binuclear NiIII-NiIII intermediate lacks a Ni−Ni bond. Each NiIII undergoes separate, but fast reductive elimination, giving rise to NiI species. The reactivity of these binuclear Ni complexes highlights the fundamental difference between Ni and Pd in mediating bond-formation processes. [ABSTRACT FROM AUTHOR]

Catalytic activities of a series of functional bipyridine-based RuII complexes in β-alkylation of secondary alcohols using primary alcohols were investigated. Bifunctional RuII complex ( 3 a) bearing 6,6'-dihydroxy-2,2'-bipyridine (6DHBP) ligand exhibited the highest catalytic activity for this reaction. Using significantly lower catalyst loading (0.1 mol %) dehydrogenative carbon−carbon bond formation between numerous aromatic, aliphatic and heteroatom substituted alcohols were achieved with high selectivity. Notably, for the synthesis of β-alkylated secondary alcohols this protocol is a rare one-pot strategy using a metal-ligand cooperative RuII system. Remarkably, complex 3 a demonstrated the highest reactivity compared to all the reported transition metal complexes in this reaction. [ABSTRACT FROM AUTHOR]

An intermolecular approach to the construction of 3,4-dihydro-1 H-pyrrolo[2,1- c][1,4]oxazines is reported for the first time using the oxa-Pictet-Spengler reaction. The method involves a sequence of carbon-carbon- and carbon-oxygen-bond formation between a substituted 2-(1 H-pyrrol-1-yl)ethan-1-ol and an aldehyde/ketone. p-Toluenesulfonic acid ( pTSA) was identified as a suitable catalyst to promote the reaction. The method provides a one-step conversion of various aldehydes/ketones into the corresponding 3,4-dihydro-1 H-pyrrolo[2,1- c][1,4]oxazines. [ABSTRACT FROM AUTHOR]

Photolysis of an iron tricarbonyl complex in the presence of 1-hexyne results in the activation of the terminal C–H bond to yield an iron–alkynyl species. The reaction proceeds through a single transition state with an activation enthalpy of 13.5 kcal mol−1. The resulting molecule may have potential as a C–C bond formation reagent. [ABSTRACT FROM AUTHOR]

A new tandem process is reported that provides access to α- hydroxyamides from epoxides for the first time. Herein, we explore InCl3-mediated tandem rearrangement of epoxides to aldehydes and α-addition of TosMIC to in situ derived aldehydes. An unprecedented C-C bond-forming reaction is disclosed that features mild conditions, high yields, and shorter reaction times. [ABSTRACT FROM AUTHOR]

A facile and efficient approach is developed for the synthesis of fluorene and its derivatives starting from 2-iodobiphenyls and CH2Br2. A range of fluorene derivatives can be synthesized under relatively mild conditions. The reaction proceeds via a tandem palladium-catalyzed dual C-C bond formation sequence through the key dibenzopalladacyclopentadiene intermediates, which are obtained from 2-iodobiphenyls through palladium-catalyzed C-H activation. [ABSTRACT FROM AUTHOR]

The first Ni-catalyzed Suzuki-Miyaura coupling of amides for the synthesis of widely occurring biaryl compounds through N−C amide bond activation is reported. The reaction tolerates a wide range of electron-withdrawing, electron-neutral, and electron-donating substituents on both coupling partners. The reaction constitutes the first example of the Ni-catalyzed generation of aryl electrophiles from bench-stable amides with potential applications for a broad range of organometallic reactions. [ABSTRACT FROM AUTHOR]

An efficient continuous flow iron-catalyzed Kumada cross-coupling was developed for the coupling of 2-chloropyrazine and various aryl Grignard reagents in presence of low catalyst loadings (0.5 mol-%). Compared to batch mode, the continuous flow approach overcomes the exothermicity which enabled longer catalyst lifetime, facilitated scale-up and significantly improved the yield. To the best of our knowledge, this is the first example of flow iron-catalyzed Kumada cross-coupling reactions which addresses scale dependence issues which often plague Kumada reactions carried out in the traditional batch mode. [ABSTRACT FROM AUTHOR]

This review covers the formation of Csp³-Csp³ bonds through Pd-catalyzed reactions of benzylic and heterobenzylic substrates bearing acetate, carbonate, phosphonate, or halide leaving groups, with malonate-type compounds, oxazoles, aldehydes, &#945,β-unsaturated aldehydes, oxindoles, or azlactones. Some of these coupling reactions have been carried out efficiently under enantioselective conditions. In most cases the reaction involves nucleophilic addition to the η³-benzylpalladium intermediate formed by elimination of the leaving group. Before the nucleophilic attack, however, this intermediate can equilibrate with another benzylpalladium complex, leading to the isomeric coupling product. Because the nucleophilic addition can lead to the dearomatization of the aryl unit, subsequent rearomatization can transform the Csp³-Csp³ bond into a Csp²- Csp³ bond. Intramolecular reactions between benzylic and nucleophilic units have been reported, as well as decarboxylative benzylations from substrates in which the leaving group contains a potential nucleophilic species. [ABSTRACT FROM AUTHOR]

A highly stereoselective formal total synthesis of brevisamide is described that proceeds through a convergent pathway and utilizes our own tandem isomerization/C-O and C-C bond formation reaction as the key step to construct the trans-2,6-disubstituted dihydropyran ring system. Other significant reactions in this synthesis include an iodolactonization, a Crimmins-modified 'non-Evans' syn aldol reaction, and a Horner-Wadsworth-Emmons olefination. [ABSTRACT FROM AUTHOR]

Diels-Alder cycloaddition reactions of 1,3,5-hexatriynes with tetraphenylcyclopentadienone have been performed, and mainly gave 1,2-diethynyl-3,4,5,6-tetraphenylbenzene derivatives as products. The Diels-Alder reactions were optimized under conventional heating and microwave irradiation conditions, and showed good selectivity towards the central carbon-carbon triple bond of the triyne. Empirical evidence suggests that the selectivity of the reaction is governed predominantly by the steric demands of the end-groups of the triyne. Several of the Diels-Alder products could be further elaborated by a sequence of desilylation and oxidative homocoupling to provide dimeric products. The homocoupling reaction was optimized by Pd catalysis. The X-ray crystallographic analysis of two derivatives is reported. [ABSTRACT FROM AUTHOR]

The radical S-adenosylmethionine (SAM) protein PqqE is predicted to function in the pyrroloquinoline quinone (PQQ) biosynthetic pathway via catalysis of carbon-carbon bond formation between a glutamate and tyrosine side chain within the small peptide substrate PqqA.Wereport here that PqqE activity is dependent on the accessory protein PqqD, which was recently shown to bind PqqA tightly. In addition, PqqE activity in vitro requires the presence of a flavodoxin- and flavodoxin reductasebased reduction system, with other reductants leading to an uncoupled cleavage of the co-substrate SAM. These results indicate that PqqE, in conjunction with PqqD, carries out the first step in PQQ biosynthesis: a radical-mediated formation of a new carbon-carbon bond between two amino acid side chains on PqqA. [ABSTRACT FROM AUTHOR]

Applications of ferromagnetic in situ generated α-Fe2O3 NPs as an efficient and recyclable catalyst for carbon–carbon bond formation via Sonogashira–Hagihara coupling reactions and the synthesis of pyran derivatives by hetero-Diels–Alder reactions have been demonstrated. This catalytic system is easily recoverable due to the ferromagnetic nature of α-Fe2O3 NPs and can be reused with sustained selectivity and activity. [ABSTRACT FROM AUTHOR]

Two novel schemes have been developed for the synthesis of the C-C fragment of the macrocyclic antitumor drug laulimalide and its analogs via transformations of cyclopropanol intermediates. [ABSTRACT FROM AUTHOR]

Nickel nanoparticles have been shown to be an accessible catalyst which allows hydrogenation of unsaturated compounds to be accomplished under atmospheric pressure of hydrogen at relatively low temperatures. Linear and cyclic alkenes, styrene and norbornene derivatives, as well as pinenes and camphene have been smoothly hydrogenated under these conditions. In some cases, selective hydrogenation of unsaturated carbon-carbon bond is possible with the other functional group remaining intact. [ABSTRACT FROM AUTHOR]

A remote RuII(terpy)2 unit incorporated in conjugation with the [NHC-RuII(para-cymene)] catalytic site, acts as a “coordination booster” for enhancing the catalytic efficiency to achieve excellent performance in selective oxidative scission of various carbon–carbon multiple bonds to the corresponding aldehydes, ketones and diketones. Generation of an active catalyst via oxidative loss of para-cymene from the precatalyst was found to be accelerated by the “coordination booster” through the electronic effect. [ABSTRACT FROM AUTHOR]

The oxidative treatment of (m)ethyl 2-aryl cinnamates equipped with methoxy groups in position 4 of the phenyl moiety promote the formation of cyclohexadienone substructures. This dealkylative oxidative C-C coupling gives access to spirocyclic compounds and avoids the construction of the corresponding phenanthrenes. Furthermore, the transformation can be expanded to other spirocyclic systems. [ABSTRACT FROM AUTHOR]

An efficient palladium-catalyzed C-O and subsequent C-C bond formation of 2,4-dichloroquinazoline have been described. The designed strategy results in the synthesis of novel 2-arylated quinazolin-4-ones framework with various aryl/heteroaryl boronic acids in moderate to good yields along with 2,4-diarylated quinazolines. This methodology offers a direct transformation of aryl halides to aryl alcohols/ketone as well as the straight forward application to generate a wide variety of monoaryl and diaryl quinazoline. [ABSTRACT FROM AUTHOR]

The selective preparation of 1,1,1-tris-(boronates) from vinylarenes and bis(pinacolato)diboron is described. The reactions occur at ambient temperature with excellent selectivity, high yields, and good functional group tolerance. Mechanistic studies suggest that Co(l)-catalyzed double dehydrogenative borylations generate a 1,1-diborylalkene intermediate, which undergoes hydroboration with pinacolborane formed in situ to yield 1,1,1-tris(boronate). [ABSTRACT FROM AUTHOR]

Hapalindoles are bioactive indole alkaloids with fascinating polycyclic ring systems whose biosynthetic assembly mechanism has remained unknown since their initial discovery in the 1980s. In this study, we describe the fam gene cluster from the cyanobacterium Fischerella ambigua UTEX 1903 encoding hapalindole and ambiguine biosynthesis along with the characterization of two aromatic prenyltransferases, FamD1 and FamD2, and a previously undescribed cyclase, FamC1. These studies demonstrate that FamD2 and FamC1 act in concert to form the tetracyclic core ring system of the hapalindoles from cis-indole isonitrile and geranyl pyrophosphate through a presumed biosynthetic Cope rearrangement and subsequent 6-exo-trig cyclization/electrophilic aromatic substitution reaction. [ABSTRACT FROM AUTHOR]

Nitrogenase catalyzes substrate reduction at its cofactor center ([(Cit)MoFe7S9C]n-; designated M-cluster). Here, we report the formation of an artificial, nitrogenasemimicking enzyme upon insertion of a synthetic model complex ([Fe6S9(SEt)2]4-; designated Fe6 RHH) into the catalytic component of nitrogenase (designated NifDKapo). Two Fe6 RHH clusters were inserted into NifDKapo, rendering the conformation of the resultant protein (designated NifDKFe) similar to the one upon insertion of native M-clusters. NifDKFe can work together with the reductase component of nitrogenase to reduce C2H2 in an ATP-dependent reaction. It can also act as an enzyme on its own in the presence of EuIIDTPA, displaying a strong activity in C2H2 reduction while demonstrating an ability to reduce CN- to C1-C3 hydrocarbons in an ATP-independent manner. The successful outcome of this work provides the proof of concept and underlying principles for continued search of novel enzymatic activities based on this approach. [ABSTRACT FROM AUTHOR]

A two-step reaction to convert terminal alkynes into triborylalkenes is reported. In the first step, the terminal alkyne and pinacolborane (HBpin) are converted into an alkynylboronate, which is catalyzed by an iridium complex supported by a SiNN pincer ligand. In the second step, treatment of the reaction mixture with CO generates a new catalyst which mediates dehydrogenative diboration of alkynylboronate with pinacolborane. The mechanism of the diboration remains unclear but it does not proceed via intermediacy of hydroboration products or via B2pin2. [ABSTRACT FROM AUTHOR]

The use of borylzinc reagents in palladium-catalyzed borylation chemistry is described (i.e. a boron analogue of the Negishi coupling), including a one-pot bench-top protocol using an air- and moisture-stable bis(boryl)zinc reagent. The steric/electronic properties of the boryl fragment employed enable a systematic method for accessing acylboranes, a rare class of organoboron species with great potential in chemical synthesis. The reactions proceed under mild conditions, use inexpensive commercial sources of palladium, and demonstrate a remarkable functional-group tolerance. [ABSTRACT FROM AUTHOR]

Enzymes and cofactors with iron-sulfur heterocubane core structures, [Fe4S4], are often found in nature as electron transfer reagents in fundamental catalytic transformations. An artificial heterocubane with a [Fe4N4] core is reported that can reversibly store up to four electrons at very negative potentials. The neutral [Fe4N4] and the singly reduced low-valent [Fe4N4]− heterocubanes were isolated and fully characterized. The low-valent species bears one unpaired electron, which is localized predominantly at one iron center in the electronic ground state but fluctuates with increasing temperatures. The electrons stored or released by the [Fe4N4]/[Fe4N4]− redox couple can be used in reductive or oxidative CC couplings and even allow catalytic one-pot reactions, which show a remarkably enhanced selectivity in the presence of the [Fe4N4] heterocubanes. [ABSTRACT FROM AUTHOR]

The nickel-catalyzed coupling of enones or enals with alkynes in the presence of silane and titanium alkoxide reductants provides direct access to skipped diene products. The process involves a net four-electron reductive coupling and proceeds with deoxygenation of the starting enone or enal. A new class of well-defined nickel(0) precatalysts bearing an unhindered N-heterocyclic carbene ligand, which was developed in optimization of the process, is essential for the efficiency of the transformation. The strategy allows the high reactivity of a,ß-unsaturated carbonyl substrates to be utilized in couplings with simultaneous extrusion of the oxygen atom, thus enabling a traceless strategy for alkene installation. [ABSTRACT FROM AUTHOR]

For the synthesis of multisubstituted dispirocyclohexane derivatives, a Rauhut-Currier-initiated organocascade reaction between 2-arylideneindan-1,3-diones and activated alkenes in the presence of diazabicyclo[2.2.2]octane (DABCO) was demonstrated. The functionalized dispirocyclohexanes with a wide range of substituents were obtained in satisfactory to excellent chemical yields (58-99%) with high chemo- and diastereoselectivities (>95:5 dr). This organocatalytic reaction proceeded smoothly through Michael/Michael cyclization, which involves the formation of three new carbon-carbon bonds with simultaneous construction of two all-carbon spiro quaternary centers. [ABSTRACT FROM AUTHOR]

A highly regio- and stereoselective C-C double bond formation reaction via Pd-catalyzed Heck-type cascade process with N-tosylhydrazones has been developed. Various N-tosylhydrazones derived from both ketones and aldehydes are found to be efficient substrates to provide di- and trisubstituted olefins with high regio- and stereoselectivity. Furthermore, this reaction has a good functional group tolerance and different benzofuran-, dihydrobenzofuran-, and indoline-containing alkene products were obtained with high selectivity. [ABSTRACT FROM AUTHOR]

PdPtZn and PdZn nanoparticle (NP) were synthesized by the reduction of [PdCl2(cod)], [PtCl2(cod)] (cod = cis, cis-1,5-cyclooctadiene) and [Zn(acac)2] (acac = acetylacetonate) complexes at an oil-water interface. The structure and morphology of the as-prepared NPs were characterized with X-ray diffraction, transmission and energy dispersive analysis of X-rays. of the prepared NPs was investigated in the in H2O-EtOH and various micellar media systems such as cetyltrimethylammonium bromide (cationic surfactant), sodium dodecylsulfate (anionic surfactant) and Pluronic P123 (non-ionic surfactant). PdPtZn and PdZn exhibited higher compared to Pd in the due to the appropriate interaction between palladium, platinum and zinc metals. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The synthesis of a C(1)–C(24) advanced southern hemisphere fragment towards the total synthesis of spirastrellolide E has been achieved. Highlights of the route include a highly convergent Type I Anion Relay Chemistry (ARC) tactic for fragment assembly, in conjunction with a directed, regioselective gold-catalyzed alkyne functionalization to generate the central unsaturated [6,6]-spiroketal. [ABSTRACT FROM AUTHOR]

There are a few reports on the reaction of tertiary alkyl halide and alkene to produce an alkyl-substituted alkene. To establish tertiary alkylation of a C-C double bond, radical reaction is found to be one of the most promising protocols. In this paper, we highlight tertiary alkyl substitutions on C-C double bonds via atom-transfer radical substitution (ATRS) catalyzed by a copper salt and introduce the corresponding M-H reactions. 1 Alkylation via the Mizoroki-Heck Reaction 2 Tertiary Alkylative M-H-Type Reaction 3 Regioselective Double-Bond Formation 4 Summary and Perspectives. [ABSTRACT FROM AUTHOR]

The article offers information a research on the application of iron catalyst in organic synthesis. Topics discussed include iron-catalyzed allylic substitutions for palladium-catalyzed counterparts, oxidative carbon-carbon bond forming reactions by cross-dehydrogenative couplings, and iron-porphyrin catalyzed cyclopropanation and hydrogen transfer ability of iron catalysts.