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An oxocarbenium-olefin cross metathesis occurs during Bronsted acid catalyzed reactions of 1H-isochromene acetals with vinyl diazo compounds. Formally a carbonyl-alkene [2 + 2]-cyclization between isobenzopyrylium ions and the vinyl group of vinyl diazoesters, the retro-[2 + 2] cycloaddition produces a tethered alkene and a vinyl diazonium ion that, upon loss of dinitrogen, undergoes a highly selective carbocationic cascade rearrangements to diverse products whose formation is controlled by reactant substituents. Polysubstituted benzobicyclo[3.3.1]oxocines, benzobicyclo[3.2.2]oxepines, benzobicyclopropane, and naphthalenes are obtained in good to excellent yields and selectivities. Furthermore, isotopic tracer and control experiments shed light on the oxocarbenium-olefin metathesis/rearrangement process as well as on the origin of the interesting substituent-dependent selectivity.

1,2,3-Triazine 1-oxides are formed by nitrosyl addition from tert-butyl nitrite to the vinylogous position of vinyl diazo compounds. This transformation, which is a formal intermolecular [5 + 1] cycloaddition, occurs under mild conditions, with high functional group tolerance and regioselectivity, and can be employed for late-stage functionalization. Upon heating at refluxing chlorobenzene temperature, these triazine-N-oxides undergo dinitrogen extrusion to form isoxazoles in very high yields.

Artemisinin is the plant natural product used to treat malaria. The endoperoxide bridge of artemisinin confers its antiparasitic properties. Dihydroartemisinic acid is the biosynthetic precursor of artemisinin that was previously shown to nonenzymatically undergo endoperoxide formation to yield artemisinin. This report discloses the synthesis of [15,15,15-2H3]-dihydroartemisinic acid and its use to determine the mechanism of endoperoxide formation. Several new observations were made: (i) Ultraviolet-C (UV-C) radiation initially accelerates artemisinin formation and subsequently promotes homolytic cleavage of the O-O bond and rearrangement of artemisinin to a different product, and (ii) dideuterated and trideuterated dihydroartemisinic acid isotopologues at C3 and C15 converted to artemisinin at a slower rate compared to nondeuterated dihydroartemisinic acid, revealing a kinetic isotope effect in the initial ene reaction toward endoperoxide formation (kH/kD ∼ 2-3). (iii) The rate of conversion from dihydroartemisinic acid to artemisinin increased with the amount of dihydroartemisinic acid, suggesting an intermolecular interaction to promote endoperoxide formation, and (iv) 18O2-labeling showed incorporation of three and four oxygen atoms from molecular oxygen into the endoperoxide bridge of artemisinin. These results reveal new insights toward understanding the mechanism of endoperoxide formation in artemisinin biosynthesis.

A new polymorph of N-tert-butyl-2-thioimidazole (1), along with its cocrystals with 1,4-diiodotetrafluorobenzene (2), tetraiodoethylene (3), and molecular iodine (4) have been synthesized. Compound 1 is a new polymorph of a previously reported structure. A series of noncovalent N–H⋯S, N–H⋯I, and I⋯S interactions all contribute to the packing. In 1–3, a pair of N–H⋯S contributes to the formation of imidazole dimers, a commonly observed motif for these systems, which are then linked together through C–I⋯S halogen bonding. This halogen bond occurs approximately normal to the imidazole ring plane. In 4, the addition of I2 to the sulfur atom interrupts N–H⋯S dimer formation, with the primary interactions between neighboring imidazole molecules being of the N–H⋯I and C=S⋯I. This variety of intermolecular interactions leads to the formation of double-stranded chains, ribbons, and sheets. A new polymorph of N-tert-butyl-2-thioimidazole, along with its cocrystals with 1,4-diiodotetrafluorobenzene, tetraiodoethylene, and molecular iodine have been synthesized. A series of noncovalent N–H⋯S, N–H⋯I, and I⋯S all contribute to the packing

An unprecedented Ag(I)-catalyzed efficient method for the coupling of β-oxoimides and enol diazoacetates through a [3+2]-cycloaddition/C-O bond cleavage/[1,5]-proton transfer cascade process is reported. The general class of imino ethers that includes oxazolines, benzoxazoles and benzimidates are applicable substrates for these reactions that provide direct access to fully substituted pyrroles with uniformly high chemo- and regioselectivity. High variability in substitution at the pyrrole 2-, 5- and N -positions characterizes this methodology that also presents an entry point for further pyrrole diversification via facile modification of resulting N -functional pyrroles.

This study probes femto- and picosecond excited-state dynamics of a series of N-heterocyclic carbene (NHC) ligand-containing platinum(II) complexes of the type trans-(NHC)2PtII(CC-Ar)2, where CC-Ar is an arylacetylide. By using femtosecond transient absorption spectroscopy, two dynamic processes are observed: an ultrafast singlet → triplet intersystem crossing (

Catalyst-directed access to divergent products involving three different metals that exclusively form three different products from the same reactants is reported. Each catalyst directs an individu...

The Co(I) complex, [Co(N2)(CyPNP)] (CyPNP = anion of 2,5-bis-(dicyclohexylphosphinomethyl)pyrrole), is active toward the catalytic hydrogenation of terminal alkenes and the semi-hydrogenation of in...

Two new platinum(II) compounds with trans-(NHC)2Pt(C≡C–C≡C–R)2 (where NHC = N-heterocyclic carbene and R = phenyl or trimethylsilyl) architecture exhibit sharp blue-green or saturated deep-blue pho...

The quest for new and unique polynuclear metal-oxocarboxylate clusters has led to a continual boom of highly connected and robust metal-organic frameworks (MOFs) with intriguing properties. In this work, by virtue of a highly specific coordination-driven cluster rearrangement process of a presynthesized trinuclear zirconocene-based tripodal metallo-pyridine ligand, we realized the preparation of the first two 2D heterometallic MOFs incorporating unprecedented Johnson-type (J51) nonanuclear Zr-oxocarboxylate clusters, as unambiguously uncovered by single-crystal X-ray crystallography. The resultant two charged frameworks feature counteranion-dependent 3,6-c kgd (JMOF-1) and 3,12-c 3,12L4 (JMOF-2) nets that are formed by octahedral and hexagonal prismatic Zr9 molecular building blocks (MBBs), respectively. In addition, JMOF-2 shows promise for the purification of acetylene from CO2 and C2H4, with IAST selectivities of about 12 and 8, respectively, at 298 K and 1 bar, as well as remarkable iodine capture capacity of up to 2.4 g g-1.

Sulfonamides feature prominently in organic synthesis, materials science and medicinal chemistry, where they play important roles as bioisosteric replacements of carboxylic acids and other carbonyls. Yet, a general synthetic platform for the direct conversion of carboxylic acids to a range of functionalized sulfonamides has remained elusive. Herein, we present a visible light-induced, dual catalytic platform that for the first time allows for a one-step access to sulfonamides and sulfonyl azides directly from carboxylic acids. The broad scope of the direct decarboxylative amidosulfonation (DDAS) platform is enabled by the efficient direct conversion of carboxylic acids to sulfinic acids that is catalyzed by acridine photocatalysts and interfaced with copper-catalyzed sulfur–nitrogen bond-forming cross-couplings with both electrophilic and nucleophilic reagents., Sulfonamides are now accessible directly from carboxylic acids by a one-step, tricomponent decarboxylative amidosulfonation that provides the missing link between the two key functionalities.

A general catalytic methodology for 1,2-RF/Y-difunctionalization of conjugated alkenes is reported. Diverse functionalized carbon radicals (RF•), which are generated through copper(I)-initiated sel...

Conjugate addition is one of the most synthetically useful carbon‒carbon bond-forming reactions, however, reactive carbon nucleophiles are typically required to effect the addition. Radical conjugate addition provides an avenue for replacing reactive nucleophiles with convenient radical precursors. Carboxylic acids can serve as simple and stable radical precursors by way of decarboxylation, but activation to reactive esters is typically necessary to facilitate the challenging decarboxylation. Here, we report a direct, dual-catalytic decarboxylative radical conjugate addition of a wide range of carboxylic acids that does not require acid preactivation and is enabled by the visible light-driven acridine photocatalysis interfaced with an efficient copper catalytic cycle. Mechanistic and computational studies provide insights into the roles of the ligands and metal species in the dual catalytic process and the photocatalytic activity of substituted acridines.

Boronic acids are centrally important functional motifs and synthetic precursors. Visible light-induced borylation may provide access to structurally diverse boronates, but a broadly efficient photocatalytic borylation method that can effect borylation of a wide range of substrates, including strong C-O bonds, remains elusive. Herein, we report a general, metal-free visible light-induced photocatalytic borylation platform that enables borylation of electron-rich derivatives of phenols and anilines, chloroarenes, as well as other haloarenes. The reaction exhibits excellent functional group tolerance, as demonstrated by the borylation of a range of structurally complex substrates. Remarkably, the reaction is catalyzed by phenothiazine, a simple organic photocatalyst with MW < 200 that mediates the previously unachievable visible light-induced single electron reduction of phenol derivatives with reduction potentials as negative as approximately - 3 V versus SCE by a proton-coupled electron transfer mechanism. Mechanistic studies point to the crucial role of the photocatalyst-base interaction.

Direct conversion of renewable biomass and bioderived chemicals to valuable synthetic intermediates for organic synthesis and materials science applications by means of mild and chemoselective catalytic methods has largely remained elusive. Development of artificial catalytic systems that are compatible with enzymatic reactions provides a synergistic solution to this enduring challenge by leveraging previously unachievable reactivity and selectivity modes. We report herein a dual catalytic dehydrodecarboxylation reaction that is enabled by a crossover of the photoinduced acridine-catalyzed O–H hydrogen atom transfer (HAT) and cobaloxime-catalyzed C–H-HAT processes. The reaction produces a variety of alkenes from readily available carboxylic acids. The reaction can be embedded in a scalable triple-catalytic cooperative chemoenzymatic lipase–acridine–cobaloxime process that allows for direct conversion of plant oils and biomass to long-chain terminal alkenes, precursors to bioderived polymers.

Dihydroartemisinic acid is the biosynthetic precursor to artemisinin, the endoperoxide-containing natural product used to treat malaria. The conversion of dihydroartemisinic acid to artemisinin is a cascade reaction that involves C-C bond cleavage, hydroperoxide incorporation, and polycyclization to form the endoperoxide. Whether or not this reaction is enzymatically controlled has been controversial. A method was developed to quantify the nonenzymatic conversion of dihydroartemisinic acid to artemisinin using LC-MS. A seven-step synthesis of 3,3-dideuterodihydroartemisinic acid (23) was accomplished beginning with dihydroartemisinic acid (1). The nonenzymatic rates of formation of 3,3-dideuteroartemisinin (24) from 3,3-dideuterodihydroartemisinic acid (23) were 1400 ng/day with light and 32 ng/day without light. Moreover, an unexpected formation of nondeuterated artemisinin (3) from 3,3-dideuterodihydroartemisinic acid (23) was detected in both the presence and absence of light. This formation of nondeuterated artemisinin (3) from its dideuterated precursor (23) suggests an alternative mechanistic pathway that operates independent of light to form artemisinin, involving the loss of the two C-3 deuterium atoms.

The PdII central atom in the title complex, [PdCl(C26H24P2)(C6H6N2O)]NO3·CH3CN or [PdCl(dppe)(INAM)]NO3·CH3CN, where dppe is 1,2-bis(diphenylphosphanyl)ethane and INAM is isonicotinamide, exists in a slightly distorted square-planar environment defined by the two P atoms of the dppe ligand, a chloride ligand and the N atom of the isonicotinamide pyridyl ring. The crystal packing in the structure is held together by hydrogen bonds between the amide of the INAM ligand and the nitrate ions that complete the outer coordination sphere. A molecule of acetonitrile is also found in the asymmetric unit of the title complex.

In the centrosymmetric title complex, [Cu2Cl2(C15H11N3)2](CF3O3S)2, the CuII metal center is fivefold coordinated by two chloride ions and three nitrogen atoms of the terpyridine ligand in a distorted square-pyramidal geometry; two trifluoromethanesulfonate ions complete the outer coordination sphere. π–π stacking interactions between the pyridyl rings in adjacent molecules contribute to the alignment of the complexes in columns along the a-axis. This structure represents the first example of a binuclear dication of formula [Cu(terpy)2Cl2]2+ with trifluoromethanesulfonate as counter-ions.

The central AgI atom of the title salt, [Ag(INAM)2](CF3SO3)·2CH3CN, where INAM is isonicotinamide (C6H6N2O), is twofold coordinated by the pyridine N atoms of two isonicotinamide ligands creating a slightly distorted linear molecular geometry. The formation of polymeric chains {[Ag(INAM)2]+} n , held together by discrete hydrogen bonds through the amide group of the INAM ligand leaves voids for non-coordinating acetonitrile molecules that interact the silver metal center via regium bonds.

Separating carbon dioxide from fuel gases like hydrocarbons by physical adsorbents is industrially important and more energy-efficient than traditional liquid extraction or cryogenic distillation methods. It is very important while very challenging to develop CO2 -selective adsorbents, considering CO2 is less polarizable than light hydrocarbon molecules, particularly those simultaneously with almost identical molecular dimensions and physical properties, such as acetylene. Herein, an ultramicroporous metal-organic framework constructed from copper(II) and 5-fluoropyrimidin-2-olate, termed Cu-F-pymo, is carefully studied under different activations for inverse separation of CO2 from C2 H2 . The partially desolvated Cu-F-pymo can exclusively capture CO2 over C2 H2 with very high selectivity exceeding 105 under ambient conditions, the highest ever reported. Sorption experiments and modeling studies reveal that such molecular sieving effect is attributed to the suppression of C2 H2 adsorption from the blockage of the preferential sites for C2 H2 by residual water molecules. The inverse separation is further confirmed by column breakthrough studies given that highly pure acetylene (>99.9%) can be directly harvested from the gas mixture. Cu-F-pymo also shows remarkable stability under harsh conditions.

Reduction of [Fe(TPC)(THF)] (TPC = trianion of 5,10,15-triphenylcorrole) with KC8 generates the iron(II) corrole anion, K(THF)2[FeII(TPC)] (3a). Compound 3a represents the first example of an isola...

The all-cis stereoisomers of tetrasubstituted azetidine-2-carboxylic acids and derivatives that possess three chiral centers have been prepared in high yield and stereocontrol from silyl-protected Z-γ-substituted enoldiazoacetates and imido-sulfur ylides by asymmetric [3+1]-cycloaddition using chiral sabox copper(I) catalysis followed by Pd/C catalytic hydrogenation. Hydrogenation of the chiral p-methoxybenzyl azetine-2-carboxylates occurs with both hydrogen addition to the C=C bond and hydrogenolysis of the ester.

Separating acetylene (C2H2) from carbon dioxide (CO2) is highly challenging under mild conditions owing to their extreme similarity in molecular properties. Herein, a mot-type microporous metal–org...

Treatment of [Fe(BH4)(CyPNP)] (CyPNP = bis(dicyclohexylphosphinomethyl)pyrrole) with 2 or 3 equiv of phosphine afforded the octahedral low-spin iron hydride compounds [FeH(PMe2Ph)(N2)(CyPNP)] and [...

The chemistry of the pyrrole-based pincer ligands, RPNP (PNP = anion of 2,5-bis(dialkylphosphinomethyl)pyrrole, R = Cy and t-Bu), with manganese is reported. Metallation of tBuPNP with Mn(II) halide precursors did not afford 1:1 ligand to metal complexes but rather led to the formation of the 2:1 complex, [Mn(κ2-N,P-tBuPNP)2]. Reduction of in situ generated tBuPNP-Mn(II) in the presence of 2,2′-bipyridine generated the apparent, high-spin Mn(I) complex, [Mn(bipy)(tBuPNP)], although metric parameters derived from crystallography demonstrated that the compound is best regarded as containing a Mn(II) ion with a bipy radical anion. Reactions of the Mn(I) precursor, [MnBr(CO)5], with RPNP afforded low-spin Mn(I) complexes of the type [Mn(CO)n(RPNP)] (R = Cy, n = 3; R = t-Bu, n = 2). A third equivalent of CO binds reversibly to [Mn(CO)2(tBuPNP)] but is lost readily. Pincer backbone dehydrogenation of [Mn(CO)n(RPNP)] with 1,4-benzoquinone produced the related complexes, [Mn(CO)n(RdPNP)] (RdPNP = anion of 2,5-bis...

N-Heterocyclic sulfones and sulfides are key functional motifs in medicinal and agricultural chemistry and important building blocks in organic synthesis. Currently available methods produce N-hete...

Development of stereoselective and efficient reactions for construction of conjugated dienes and polyenes has remained at the forefront of organic chemistry, due to their key roles in medicinal chemistry, organic synthesis, and materials science. The synthesis of conjugated dienes and polyenes is typically accomplished in a multistep manner by sequential installation of individual C=C bonds because it allows for control of stereoselectivity and efficiency of formation of each double bond. A conceptually distinct dienylation approach entails a stereoselective appendage of a four-carbon unit, shortcutting diene synthesis. Dienylation with sulfolene provided a direct route to E-dienes, but the synthesis of substantially more challenging Z-dienes remained elusive. Here, we report that a highly Z-selective dienylation can be now achieved by a simple adjustment of a ligand, enabling stereodivergent synthesis of E- and Z-dienes from one reagent and in one step. A detailed mechanistic investigation of the E- and Z-selective dienylation provided insight into the divergent behavior of the two catalytic systems and revealed that differences in relative stabilities of catalytically active palladium phosphine complexes have a major impact on the stereochemical outcomes of the dienylation.

The synthesis, characterization and catalytic activities of two homodinuclear Cu(II) and Zn(II) complexes of a carboxylate-rich ligand, N,N′-Bis[2-carboxybenzomethyl]-N,N′ -Bis[carboxymethyl]-1,3-diaminopropan-2-ol (H5ccdp) ligand towards the hydrolysis of (p-nitrophenyl phosphate) (PNPP) and bis(p-nitrophenyl) phosphate (BNPP) substrates in aqueous systems are described. Kinetic investigations were carried out using UV–Vis spectrophotometric techniques at 25 °C and 37 °C and different pH (7–10) conditions. The kinetic studies revealed that the turnover rate (kcat) values among the PNPP hydrolysis systems, the highest and the lowest kcat values were displayed by [Cu2(ccdp)(μ-OAc)]2− at 2.34 × 10−6 s−1 (pH 8 and 37 °C) and 2.13 × 10−8 s−1 (pH 8 and 25 °C), respectively. However, similar comparisons among the BNPP hydrolysis revealed that highest and the lowest kcat values were displayed by [Zn2(ccdp)(μ-OAc)]2− at 4.64 × 10−8 s−1 (pH 9 and 37 °C) and 2.38 × 10−9 (pH 9 and 25 °C). Significantly enough, the catalyst−substrate adduct species containing a metal bound PNPP and BNPP have been detected by ESI-MS techniques. Additionally, a PNPP-bound copper complex has been isolated and crystalized using single crystal X-ray diffraction technique. Based on the structural and activity information obtained in this study, reaction mechanisms for the hydrolysis of PNPP have been proposed.

The cinchona thiourea moiety in the self-assembled modularly designed organocatalysts (MDOs) switches off the iminium catalysis of these catalysts. In this study, it was found that the inhibited iminium catalysis could be switched on by using an appropriate weak acid and that, once the iminium catalysis was switched on, these catalysts could be applied for the highly stereoselective and diastereodivergent synthesis of 4-oxocyclohexanecarbaldehydes via a domino reaction between ketones and α,β-unsaturated aldehydes.

The formation of nitrile oxides with diazocarbonyl compounds by nitrosyl transfer from tert-butyl nitrite under mild conditions and without the use of a catalyst or an additive is reported. This tr...

The central copper(II) atom of the title salt, {[Cu(CF3SO3)(CH3CN)2(C12H12N2O2)](CF3SO3)} n or [[Cu(CH3CN)2(diOMe-bpy)(CF3SO3)](CF3SO3)] n where diOMe-bpy is 4,4′-dimethoxy-2,2′-bipyridine, C12H12N2O2, is sixfold coordinated by the N atoms of the chelating bipyridine ligand, the N atoms of two acetonitrile molecules, and two trifluoromethanesulfonate O atoms in a tetragonally distorted octahedral shape. The formation of polymeric chains [Cu(CH3CN)2(diOMe-bpy)(CF3SO3)]+ n leaves voids for the non-coordinating trifluoromethanesulfonate anions that interact with the complex through weak hydrogen bonds. The presence of weakly coordinating ligands like acetonitrile and trifluoromethanesulfonate makes the title compound a convenient starting material for the synthesis of novel metal–organic frameworks.

In the title complex, [Zn(CF3O3S)Cl(C15H10ClN3)]·CH3CN, the zinc(II) core is fivefold coordinated by one chloride, one trifluoromethanesulfonate O atom and three terpyridine N atoms in a slightly distorted square-pyramidal geometry. The structure provides a distinct example amongst other zinc(II) 4-chloroterpyridine complexes because of the unusual planarity of the coordinated chloride, the short length of the Zn—N bond opposite to the chloride ligand [1.9572 (15) Å], and the presence of an elongated Zn—O bond [2.3911 (14) Å] in the coordinated trifluoromethanesulfonate ion. A molecule of acetonitrile is also found in the asymmetric unit of the title complex.

The cobalt(I) pincer complex, [Co(N2)(CyPNP)] (CyPNP = anion of 2,5-bis((dicyclohexylphosphino)methyl)pyrrole), reacts with aromatic, vinylic, and aliphatic aldehydes to produce the corresponding hydrocarbon products and [Co(CO)(CyPNP)]. The pathway for aldehyde decarbonylation is found to involve initial coordination of the aldehyde to Co(I), followed by oxidative addition of the C–H bond to produce a cobalt(III) acyl hydride. The acyl hydride species then undergoes CO deinsertion, followed by reductive elimination to afford the decarbonylated product and [Co(CO)(CyPNP)]. Reactions of [Co(N2)(CyPNP)] with other carbonyl containing groups such as carboxylic acids and amides also proceed via oxidative addition to give Co(III) intermediates arising from activation of the X–H (X = O or NH) bond. In these cases, however, the Co(III) species extrude molecular hydrogen to produce Co(II) species of the form [Co(X{O}CR)(CyPNP)] (X = O or NH). The ability of [Co(N2)(CyPNP)] to undergo facile oxidative addition is ...

Conjugated dienes and polyenes are central structural motifs of natural products, and key synthetic intermediates in organic synthesis and materials science. We describe herein a palladium-catalyzed dienylation of aryl, heteroaryl, and vinyl triflates, nonaflates and iodides that were previously identified as recalcitrant substrates for the sulfolene-mediated catalytic dienylation. The method has now been successfully expanded to C O and C I dienylation, demonstrating broad scope with respect to sulfonates, iodides and sulfolenes. The reactions proceed with high regio- and stereoselectivity, and efficiency that are strongly influenced by basic additives, whose influence on the reaction performance was systematically studied.

Treatment of both [CoCl(tBuPNP)] and [NiCl(tBuPNP)] (tBuPNP = anion of 2,5-bis((di-tert-butylphosphino)methyl)pyrrole) with one equivalent of benzoquinone affords the corresponding chloride complexes containing a dehydrogenated PNP ligand, tBudPNP (tBudPNP = anion of 2,5-bis((di-tert-butylphosphino)methylene)-2,5-dihydropyrrole). Dehydrogenation of PNP to dPNP results in minimal change to steric profile of the ligand but has important consequences for the resulting redox potentials of the metal complexes resulting in the ability to isolate both [CoH(tBudPNP)] and [CoEt(tBudPNP)], which are more challenging (hydride) or not possible (ethyl) to prepare with the parent PNP ligand. Electrochemical measurements with both the Co and Ni dPNP species demonstrate a substantial shift in redox potentials for both the M(II/III) and M(II/I) couples. In the case of the former, oxidation to trivalent Co was found to be reversible, and subsequent reaction with AgSbF6 afforded a rare example of a square-planar Co(III) species. Corresponding reduction of [CoCl(tBudPNP)] with KC8 produced the diamagnetic Co(I) species, [Co(N2)(tBudPNP)]. Further reduction of the Co(I) complex was found to generate a rare pincer-based π-radical anion that demonstrated well-resolved EPR features to the four hydrogen atoms and lone nitrogen atom of the ligand with minor contributions from cobalt and coordinated N2. Changes in the electronic character of the PNP ligand upon dehydrogenation are proposed to result from loss of aromaticity in the pyrrole ligand resulting in a more reducing central amido donor. DFT calculations on the Co(II) complexes were performed to shed further insight into the electronic structure of the pincer complexes.

Enoldiazoimides, a new subclass of enoldiazo compounds, generate enol-substituted carbonyl ylides whose reactions with sulfur ylides enable an unprecedented formal [4+2] cycloaddition. The resulting multifunctionalized indolizidinones, which incorporate sulfur, are formed in good yields under mild reaction conditions. The uniqueness of this transformation stems from the role of the silyl-protected enol, since the corresponding acetyldiazoimide failed to provide any cross-products in metal-catalyzed reactions with sulfur ylides. This copper-catalyzed cycloaddition is initiated with the generation of enol-substituted carbonyl ylides and sulfur ylides from enoldiazoimides and sulfonium salts, respectively, and proceeds through stepwise six-membered ring formation, C-O and C-S bond cleavage, and silyl and acetyl group migration.

The synthesis of a square-planar cobalt(II) hydrido complex supported by a pyrrole-based PNP ligand has been reinvestigated and its reactivity with various small molecules examined. Preparation of the complex was accomplished by treatment of the corresponding chloride complex, [CoCl(tBuPNP)] (tBuPNP = anion of 2,5-bis((di-tert-butylphosphino)methyl)pyrrole), with di-iso-butylaluminum hydride (DIBAL). Reaction of [CoCl(tBuPNP)] with other hydride sources such as NaEt3BH and LiAlH4 resulted in mixtures of the desired Co(II) hydride along with the reduced Co(I) species, [Co(N2)(tBuPNP)], as the primary product. The hydride complex exhibits facile migratory insertion chemistry with CO2 producing the corresponding Co(II) formate complex. When the Co–H complex is reacted with nitric oxide, the first example of a cobalt nitrosyl hydride complex is produced.

We present herein an efficient and practical method for a gram scale synthesis of 3-sulfolenes using sodium metabisulfite as a safe, inexpensive, and easy to handle sulfur dioxide equivalent. Diversely-substituted 3-sulfolenes can be prepared by reacting a variety of 1,3-dienes or allylic alcohols with sodium metabisulfite in aqueous hexafluoroisopropanol (HFIP) or in aqueous methanol in the presence of potassium hydrogen sulfate. Advantageously, the method enables conversion of allylic acohols directly to 3-sulfolenes, by-passing intermediate 1,3-dienes.

Treatment of FeCl2(thf)1.5 with the pincer ligand bis(dicyclohexylphosphinomethyl)pyrrolide (CyPNP) in the presence of 2,2′-bipyridine (bipy) affords the six-coordinate complex [FeCl(bipy)(CyPNP)]. The chloride complex exhibits spin-crossover behavior and serves as a starting point for a series of bipy-coordinated iron(II) pincer compounds, including the hydride species [FeH(bipy)(CyPNP)]. Chemical reduction of [FeCl(bipy)(CyPNP)] generates the new complex [Fe(bipy)(CyPNP)], which is found to be consistent with a structure featuring iron(I) as opposed to a bipy radical anion. Reactivity studies with the bipy complexes demonstrate that they are more prone to migratory insertion and β-hydrogen elimination reactions than the corresponding dicarbonyl analogues and that in certain instances the bipy ligand can be sequestered by treatment with a Lewis acid. These observations demonstrate that coordination of bipyridine to pincer-ligated iron(II) species provides a means of stabilizing otherwise unstable compoun...

The title structures, [Zn2(C3H6NS2)4(C14H14N4O2)]·2C3H7NO (I) and [Zn2(C7H14NS2)4(C14H14N4O2)] (II), each feature a bidentate, bridging bipyridyl-type ligand encompassing a di-amide group. In (I), the binuclear compound is disposed about a centre of inversion, leading to an open conformation, while in (II), the complete molecule is completed by the application of a twofold axis of symmetry so that the bridging ligand has a U-shape. In each of (I) and (II), the dithiocarbamate ligands are chelating with varying degrees of symmetry, so the zinc atom is within an NS4set approximating a square-pyramid for (I) and a trigonal-bipyramid for (II). The solvent dimethylformaide (DMF) molecules in (I) connect to the bridging ligandviaamide-N—H...O(DMF) and various amide-, DMF-C—H...O(amide, DMF) interactions. The resultant three-molecule aggregates assemble into a three-dimensional architectureviaC—H...π(pyridyl, chelate ring) interactions. In (II), undulating tapes sustained by amide-N—H...O(amide) hydrogen bonding lead to linear supramolecular chains with alternating molecules lying to either side of the tape; no further directional interactions are noted in the crystal.

Highly selective divergent cycloaddition reactions of enoldiazo compounds and α-diazocarboximides catalyzed by copper(I) or dirhodium(II) have been developed. With tetrakis(acetonitrile)copper(I) tetrafluoroborate as the catalyst epoxypyrrolo[1,2-a]azepine derivatives were prepared in good yields and excellent diastereoselectivities through the first reported [3+3]-cycloaddition of a carbonyl ylide. Use of Rh2 (pfb)4 or Rh2 (esp)2 directs the reactants to regioselective [3+2]-cycloaddition generating cyclopenta[2,3]pyrrolo[2,1-b]oxazoles with good yields and excellent diastereoselectivities.

We report herein a photoinduced carboborative ring contraction of monounsaturated six-membered carbocycles and heterocycles. The reaction produces substituted five-membered ring systems stereoselectively and on preparative scales. The products feature multiple stereocenters, including contiguous quaternary carbons. We show that the reaction can serve as a synthetic platform for ring system alteration of natural products. The reaction can also be used in natural product synthesis. A concise total synthesis of artalbic acid has been enabled by a sequence of photoinduced carboborative ring contraction, Rauhut-Currier reaction, and nitrilase-catalyzed hydrolysis. The synthetic utility of the reaction has been further demonstrated by converting the intermediate organoboranes to alcohols, amines, and alkenes.

Solvothermal reaction of 3-aminoisonicotinic acid (Haina) and Cu(NO 3 ) 2 ·2.5H 2 O gave a novel two-dimensional (2D) microporous metal–organic framework, [Cu(aina) 2 (DMF)]·DMF ( 1 , DMF = N,N-dimethylformamide). Single-crystal X-ray crystallographic study of compound 1 revealed that Cu(II) ions are linked by aina − ligands forming square grid-like layers, which stack together via multiple hydrogen bonding interactions. The solvent-free framework of 1a displayed considerable porosity (void = 46.5%) with one-dimensional (1D) open channels (4.7 A × 4.8 A) functionalized by amino groups. Gas sorption measurements of 1 revealed selective carbon dioxide (CO 2 ) and acetylene (C 2 H 2 ) adsorption over methane (CH 4 ) and nitrogen (N 2 ) at ambient temperature.

The title compound, {[Zn(C9H11N2S2)2]·0.5C6H7N} n , comprises two independent, but chemically similar, Zn[S2CN(Et)CH2py]2 residues and a 4-methylpyridine solvent molecule in the asymmetric unit. The Zn-containing units are connected into a one-dimensional coordination polymer (zigzag topology) propagating in the [010] direction, with one dithiocarbamate ligand bridging in a μ2-κ3 mode, employing one pyridyl N and both dithiocarbamate S atoms, while the other is κ2-chelating. In each case, the resultant ZnNS4 coordination geometry approximates a square pyramid, with the pyridyl N atom in the apical position. In the crystal, the chains are linked into a three-dimensional architecture by methyl- and pyridyl-C—H...S, methylene-C—H...N(pyridyl) and pyridyl-C—H...π(ZnS2C) interactions. The connection between the chain and the 4-methylpyridine solvent molecule is of the type pyridyl-C—H...N(4-methylpyridine).

The first cyclization reactions of enoldiazo compounds with nitrosoarenes have been developed. Under the catalysis of rhodium(II) octanoate, [3 + 2]-cyclization between enoldiazoacetamides and nitrosoarenes occurred through cleavages of the enol double bond and the amide bond, thus furnishing fully substituted 5-isoxazolone derivatives. Upon changing the catalyst to rhodium(II) caprolactamate, the reaction pathway switched to an unprecedented formal [5 + 1]-cyclization that provided multifunctionalized 1,3-oxazin-4-ones with near exclusivity under otherwise identical conditions. Mechanistic studies uncovered distinct catalytic activities and reaction intermediates, which plausibly rationalized the novel reactivity and catalyst-controlled chemodivergence. Furthermore, a mechanism-inspired enantioselective rhodium-catalyzed reaction of γ-substituted enoldiazoacetamide with nitrosobenzene produced highly enantioenriched heterocycle-linked trialkylamine.

Selective separation of acetylene (C2H2) from carbon dioxide (CO2) or ethylene (C2H4) needs specific porous materials whose pores can realize sieving effects while pore surfaces can differentiate their recognitions for these molecules of similar molecular sizes and physical properties. We report a microporous material [Zn(dps)2(SiF6)] (UTSA-300, dps = 4,4′-dipyridylsulfide) with two-dimensional channels of about 3.3 A, well-matched for the molecular sizes of C2H2. After activation, the network was transformed to its closed-pore phase, UTSA-300a, with dispersed 0D cavities, accompanied by conformation change of the pyridyl ligand and rotation of SiF62– pillars. Strong C–H···F and π–π stacking interactions are found in closed-pore UTSA-300a, resulting in shrinkage of the structure. Interestingly, UTSA-300a takes up quite a large amounts of acetylene (76.4 cm3 g–1), while showing complete C2H4 and CO2 exclusion from C2H2 under ambient conditions. Neutron powder diffraction and molecular modeling studies clea...

Treatment of FeCl2(thf)1.5 with the sodium salt of bis(dicyclohexylphosphinomethyl)pyrrole (NaCyPNP) in the presence of pyridine (py) affords the high-spin, five-coordinate iron(II) complex [FeCl(py)(CyPNP)]. The chloride complex serves as a starting point for a variety of organometallic iron(II) compounds including S = 1 square planar alkyls, [FeR(CyPNP)] (R = Me, Et, Bn, Ph). Treatment of [FeCl(py)(CyPNP)] with NaBEt3H does not generate an analogous square-planar hydride complex, but rather a bimetallic high-spin iron(II) species containing bridging hydride ligands. Analogous transmetalation reactions in the presence of carbon monoxide produced six-coordinate low-spin species [FeR(CO)2(CyPNP)] (R = Et, Ph, and H). Reduction of [FeCl(py)(CyPNP)] under CO afforded the low-spin iron(I) carbonyl complex [Fe(CO)2(CyPNP)]. This species could be further reduced with KC8 to afford the anionic iron(0) complex K[Fe(CO)2(CyPNP)]·thf. The breadth of coordination numbers, spin states, and valencies supported by this...