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Biomimetic modularization and function-oriented synthesis of structurally diversified natural product-like macrocycles in a step-economical fashion is highly desirable. Inspired by marine furanocembranoids, herein, we synthesize diverse alkenes substituted furan-embedded macrolactams via a modular biomimetic assembly strategy. The success of this assembly is the development of crucial Pd-catalyzed carbene coupling between ene-yne-ketones as donor/donor carbene precursors and unactivated Csp3‒H bonds which represents a great challenge in organic synthesis. Notably, this method not only obviates the use of unstable, explosive, and toxic diazo compounds, but also can be amenable to allenyl ketones carbene precursors. DFT calculations demonstrate that a formal 1,4-Pd shift could be involved in the mechanism. Moreover, the collected furanocembranoids-like macrolactams show significant anti-inflammatory activities against TNF-α, IL-6, and IL-1β and the cytotoxicity is comparable to Dexamethasone.

Three-membered unsaturated rings have been widely utilized in organic synthesis due to their inherent highly strained structures. Although much research has been applied to ring-expansion reactions...

The reactions of the rhenium(III)-phosphine complex ReCl3(PMePh2)3 with organonitriles (NCR) were studied and found to give novel addition as well as simple substitution products. Refluxing ReCl3(P...

The detailed reaction mechanisms of gold-catalyzed reactions of 2,1-benzisoxazoles with propiolates and ynamides have been investigated with the aid of density functional theory calculations. Our investigation focused on the different selectivities observed for the reactions of the two different classes of substituted alkynes. Through our systematic calculations, we found that the catalytic reactions start with a nucleophilic nitrogen atom attacking one coordinated alkyne carbon. Then, an N–O bond cleavage takes place to give two different gold carbenoid intermediates, from which four possible pathways lead to different products (7-acylindolyl derivatives and quinolone oxides). In the reaction of 2,1-benzisoxazole (anthranil) with the propiolate PhCCCOOMe, the relevant N–O bond cleavage leading to the 7-acylindolyl product is only slightly less favorable than that leading to the quinolone oxide product. The steps following the N–O bond cleavage are all very facile. Therefore, the N–O bond cleavage step is responsible for the selective outcome observed experimentally. In the reaction of 2,1-benzisoxazole (anthranil) with the ynamide PhCCNMeMs, the N–O bond cleavages leading to the 7-acylindolyl product and the quinolone oxide have comparable barriers. However, the C–N coupling that followed has a very high barrier, making the pathway leading to the quinolone oxide product unfavorable. As a result, only the 7-acylindolyl product is experimentally observed.

A metal-free access to 3-allyl-2-alkoxychromanones by PPh3-catalyzed alkoxy allylation of chromones with MBH carbonates and alcohols is described. This reaction is performed under mild conditions and it shows good functional group tolerance, providing a series of functionalized chromanones in moderate to high yields with excellent diastereoselectivities. Deuterium-labeling experiments to probe a possible mechanism and scale-up reaction were also conducted.

Anthranilic acids (AAs) are significant basic chemicals used in pharmaceuticals, agrochemicals, dyes, fragrances, etc. Superfluous steps are always involved in obtaining AAs. Herein, we demonstrate a straightforward strategy to transform abundant o-nitrotoluenes into biologically and pharmaceutically significant AAs without any extra reductants, oxidants and protecting groups. Various sensitive groups, such as halogens, sulfide, aldehyde, pyridines, quinolines, etc., can be tolerated in this transformation. A hundred-gram-scale operation is realized efficiently with almost quantitative selenium recycling. Further mechanistic studies and DFT calculations disclosed the proposed atom-exchange processes and the key roles of the selenium species.

A di(o-tolyl)borylgold complex was synthesized via the metathesis reaction of a gold alkoxide with tetra(o-tolyl)diborane(4). The resulting diarylborylgold complex exhibited a Lewis acidic boron center and a characteristic visible absorption that arises from its HOMO–LUMO excitation, which is narrower than that of a previously reported dioxyborylgold complex. The diarylborylgold complex reacted with isocyanide in a stepwise fashion to afford single- and double-insertion products and a C–C coupled product. Reactions of this diarylborylgold complex with C Created by potrace 1.16, written by Peter Selinger 2001-2019 O/N double bond species furnished addition products under concomitant formation of Au–C and B–O/N bonds, which suggests nucleophilic reactivity of the gold metal center. DFT calculations provided details of the underlying reaction mechanism, which involves an initial coordination of the CO/N bond to the boron vacant p-orbital of the diarylboryl ligand followed by a migration of the gold atom from the tetracoordinate sp3-hybridized boron center, which is analogous to the reactivity of the conventional sp3-hybridized borate species. The DFT calculations also suggested a stepwise mechanism for the reaction of this diarylborylgold complex with isocyanide, which afforded three different reaction products depending on the applied reaction conditions., A di(o-tolyl)borylgold complex added to CO/N double bond to form Au–C and B–O/N bonds. DFT calculations revealed a two-step mechanism consisting of the coordination of O/N atom to B atom followed by nucleophilic migration of Au atom.

Transition metal-free direct and base-catalyzed 1,2-diborations of arylacetylenes using pinB-BMes2 provided a syn/anti-isomeric mixture of diborylalkenes. The kinetic analysis showed that the reaction rate and isomer ratio were affected by reaction conditions and substituents on the aryl ring. DFT calculations indicated that direct addition proceeded via the interaction of acetylene-π with the BMes2 fragment. In contrast, for the base-catalyzed diboration, the previously isolated sp2–sp3 diborane and borataallene were confirmed as stable intermediates by calculations. The whole reaction pathways can be divided into the Bpin-migration and deprotonation steps, where the borataallene should be considered as a common intermediate. It should be noted that the deprotonation step is reversible and affords the kinetically less favoured isomer under the thermodynamic conditions. As a result, the composition of isomeric products, in the base-catalyzed diboration, is attributed to the small difference of activation barriers between direct and base-catalyzed systems.

DFT calculations have been performed to study the relative preference of different unsaturated organic molecules (CO2, PhCHO and styrene) for insertion into different Cu–X (X = B, C, O) bonds, which are competing processes in copper-catalyzed three-component boracarboxylation reactions involving CO2 and B2pin2. In this work, the variations in the insertion barriers and in the relative stability of the insertion products have been systematically analyzed and discussed in-depth. Our DFT calculations also allow us to make a prediction that when both aldehyde and styrene are present with CO2 and B2pin2, styrene will undergo the three-component boracarboxylation reaction rather than the aldehyde.

Despite the long history of research in transition metal (TM) complexes, the study of TM-aluminyl complexes is still in its early stage of development. It is expected that the presence of an electropositive Al donor atom would open up new possibilities in TM complex reactivity, and indeed TM-aluminyl has shown an early sign of success in small-molecule activation. On the other hand, the existing reports on TM-aluminyl reactivity are often explained to readers with different understanding on individual cases, and a general picture of TM-aluminyl reactivity is still not available. In this work, we have attempted to provide a systematic picture to explain some early explorations in this field, specifically a series of recently reported heteroallene insertion reactions involving unsupported TM-aluminyl complexes. Through density functional theory calculations of a number of TM-aluminyl complexes, covering both Au and Cu centers, we found that their reactivity against heteroallenes (including CO

OBJECTIVES We recently reported a high rate of nontherapeutic thymectomy. Mediastinal lymphomas (MLs) are the malignancies most likely to be confused with thymic epithelial tumours (TETs). This study aimed to establish a predictive model by evaluating clinical variables and positron emission tomography to distinguish those diseases. METHODS From 2018 to 2021, consecutive patients who were pathologically diagnosed with TETs or MLs were retrospectively reviewed. Univariable and multivariable analyses were used to identify association factors. The Akaike information criterion was used to select variables. A nomogram was developed and validated to differentiate MLs from TETs. RESULTS A total of 198 patients were included. Compared with TETs, patients with MLs were more likely to be younger with higher metabolic tumour volume (154.1 vs 74.6 cm3), total lesion glycolysis (1388.8 vs 315.2 g/ml cm3), SUVmean (9.2 vs 4.8), SUVpeak (12.9 vs 6.3) and SUVmax (14.8 vs 7.5). A nomogram was established based on the stepwise regression results and the final model containing age and SUVmax had minimal Akaike information criterion value of 72.28. Receiver operating characteristic analyses indicated that the area under the curve of predictive nomogram in differentiating MLs from TETs was 0.842 (95% CI: 0.754–0.907). The internal bootstrap resampling and calibration plots demonstrated good consistence between the prediction and the observation. CONCLUSIONS Combination of age and SUVmax appears to be a useful tool to differentiate MLs from TETs. The novel predictive model prevents more patients from receiving nontherapeutic thymectomy.

The iminoboryl

First-row transition-metal catalysis has been attracting great attention in recent years, partly due to its low toxicity and low cost, as well as a wide variety in reactivities. However, the theore...

The rhodium-catalyzed deoxygenation and borylation of ketones with B2pin2 have been developed, leading to efficient formation of alkenes, vinylboronates, and vinyldiboronates. These reactions feature mild reaction conditions, a broad substrate scope, and excellent functional-group compatibility. Mechanistic studies support that the ketones initially undergo a Rh-catalyzed deoxygenation to give alkenes via boron enolate intermediates, and the subsequent Rh-catalyzed dehydrogenative borylation of alkenes leads to the formation of vinylboronates and diboration products, which is also supported by density functional theory calculations.

A systematic theoretical study has been performed with the aid of density functional theory (DFT) calculations on the mechanism of asymmetric 1,4-dearomatization of free pyridine with styrene and d...

The first enantioselective alkynylation of benzylic C-H bonds via copper-catalyzed radical relay has been established herein, which provides an easy access to structurally diverse benzylic alkynes in good yields with excellent enantioselectivities. A key step for the asymmetric copper-catalyzed radical relay process is the enantioselective capture of a benzylic radical with chiral (Box)CuII-alkynyl species. In addition, the reaction displays good functional group tolerance, broad substrate scope, and mild conditions. The enantioenriched alkynylation products can be readily transformed into highly valuable synthons, such as chiral terminal alkynes, allenes, alkenes, and carboxylic acids. More importantly, our methodology can be applied to the synthesis of bioactive molecule AMG 837.

Gold nanoclusters are attractive because of their electronic and optical properties. Many theoretical models have been proposed to explain their electronic structures through an electron-counting approach. However, subtle features may not be well explained by electron-counting rules. In this work, we have discovered a unique example of ligand-controlled skeletal bonding in two recently reported gold nanoclusters with very similar compositions and geometries. We have shown that the superatomic orbitals of the common kernel of the two clusters undergo different ligand-field splitting because of the different ligand-field strengths in the two clusters. Such a difference is clearly revealed by constructing the Jellium orbitals via an orbital alignment process, and a subsequent localization of the Jellium orbitals allows us to obtain localized bonding models. Finally, on the basis of localized bonding models, we predict the existence of a ligated gold cluster with a [Au

[(η6-p-cymene)OsI2]2 was found to be a good catalyst for the cyclopropanation reaction of isobutyl vinyl ether with 3-tert-butyldiazoindene. In contrast, the complexes [(η6-p-cymene)OsX2]2 (X = Cl,...

Background Glioma is one of the important diseases that threaten human survival in today's society. WD repeat domain 5 (WDR5) belongs to the components of the lysine methyltransferase complex. WDR5 is involved in gene transcription regulation, cell senescence, cancer and other biological events through methylation modification. However, its expression and function in glioma are still unclear. Materials and methods The expression of WDR5 was observed in glioma cells, and then a glioma cell line SW1783 knocked down WDR5 was established. The effects of the decrease of WDR5 expression on proliferation, migration, invasion and EMT of glioma cells were detected, respectively. The downstream regulators of WDR5 were identified by gene expression profiling technology, and the possible molecular mechanisms were identified. Results In this study, we found that WDR5 could promote glioma cell's proliferation, migration, invasion and tumor metastasis. In glioma, especially in metastatic glioma tissues, WDR5 levels were significantly increased, the higher expression level could also cause a significant reduction in overall survival of glioma patients. Second, the ability of cells' proliferation, migration, invasion and tumor metastasis was significantly reduced in WDR5 knockdown cell lines. We also found a significant change in the expression level of epithelial and mesenchymal markers in WDR5 knockdown cell lines. Furthermore, we found that knockdown of WDR5 could inhibit the expression of zinc finger E-box binding homeobox 1 (ZEB1), and knockdown of ZEB1 could inhibit invasion, migration and epithelial-mesenchymal transformation (EMT) in WDR5 over-expression cell line. We also found that WDR5 may regulate ZEB1's expression through H3K4me3. Conclusion In summary, in this study, we have studied the relationship between WDR5 and glioma, and found that WDR5's expression is positively correlated with the proliferation, migration, and invasion of glioma cells, which will help find the potential therapeutic target for glioma patients.

Ionic hydrogenation has not been extensively explored, but is advantageous for challenging substrates such as unsaturated intermediates. Reported here is an iridium-catalyzed hydrogenation of oxocarbenium ions to afford chiral isochromans with high enantioselectivities. A variety of functionalities are compatible with this catalytic system. In the presence of a catalytic amount of the Brønsted acid HCl, an α-chloroether is generated in situ and subsequentially reduced. Kinetic studies suggest first-order kinetics in the substrate and half-order kinetics in the catalyst. A positive nonlinear effect, together with the half kinetic order, revealed a dimerization of the catalyst. Possible reaction pathways based on the monomeric iridium catalyst were proposed and DFT computational studies revealed an ionic hydrogenation pathway. Chloride abstraction and the cleavage of dihydrogen occur in the same step.

Reactions of OsCl2(PPh3)3 with o-ethynylphenyl-carbonyl compounds o-HC≡CC6H4C(O)R (2, R = H (a) and Et (b)) produced the η3-o-ethynylphenyl-carbonyl complexes OsCl2(PPh3)2{η3-(o-HC≡CC6H4C(O)R)} (3)...

A highly efficient asymmetric synthesis of chiral thiochromanones is developed via Cu(I)/phosphoramidite catalyzed asymmetric alkynylation of thiochromones under mild reaction conditions. The catalyst system is tolerant of various thiochromone precursors and terminal alkynes. The established asymmetric transformation provides different enatiomeric-enriched thiochromanones with more molecular complexity and enables access to chiral thioflavanones, a subgroup of flavonoid by further functionalization.

A systematic theoretical study has been carried out with the aid of density functional theory (DFT) calculations on the mechanism of the Rh-catalyzed cycloisomerization of homopropargylallene-alkynes through C(sp3)–C(sp) bond activation. The DFT results indicate that the catalytic cycle is divided into four main processes involving oxidative coupling, insertion, 1,3-alkyl migration, and 1,2-alkyl migration or 1,2-H migration. It is found that a Rh(I) Fischer carbene intermediate, which is derived from the third process 1,3-alkyl migration, selectively determines the formation of the six/five/five tricycle Product 1 or the six/five/four tricycle Product 2, depending on the substitutes on the substrates. The origin of cycloisomerization product selectivity has also been addressed.

Aside from simple Lewis acid-base chemistry, the reaction chemistry of aluminacyclopentadienes, which are commonly referred to as aluminoles or simply alumoles, remains relatively underdeveloped. To date, few attempts to extend their inherent insertion and cycloaddition reactivity to the construction of stable aluminum-containing heterocycles have been reported. Herein, we demonstrate the selective ring expansion of a cyclopentadienyl-substituted alumole with a series of organic azides to form unsaturated six-membered AlN heterocycles. Depending on the substituent on the azide, the reaction proceeds either with or without loss of dinitrogen, leading to incorporation of only the "NR" unit of the azide or the entire azo substituent into the periphery of the heterocycle. A deeper understanding of these ring expansion reactions is reached through computational studies, illustrating deviations in the mechanism as a function of the organic azide employed.

Dewar benzenes, the metastable valence isomers of benzenes, have been extensively studied both experimentally and theoretically. In contrast, little is known about Dewar metallabenzenes having a transition metal in the skeletal framework, despite the recent intensive interest in the development of chemistry of metallabenzenes. Herein, we report the isolation and characterization of the first examples of structurally characterized Dewar metallabenzenes. These compounds were generated via unprecedented reactions of metallacyclobutadienes with aminoalkynes.

We report a transition metal-free, regio- and stereo-selective, phosphine-catalyzed method for the trans hydroboration of 1,3-diynes with pinacolborane that affords (E)-1-boryl-1,3-enynes. The reaction proceeds with excellent selectivity for boron addition to the external carbon of the 1,3-diyne framework as unambiguously established by NMR and X-ray crystallographic studies. The reaction displays a broad substrate scope including unsymmetrical diynes to generate products in high yield (up to 95 %). Experimental and theoretical studies suggest that phosphine attack on the alkyne is a key process in the catalytic cycle.

A facile strategy to prepare halogenated cationic BC-centered organoboron analogues of alkenyl halides via the reaction between carbodiphosphoranes (CDPs) and aryl dihaloboranes is reported. Structural comparison of the halogen and alkoxy derivatives, as well as detailed computational studies, corroborates the polarized double dative bonding nature of the central BC double bonds.

Described here is a direct catalytic asymmetric functionalization of unactivated alkyl indoles using organocatalysis. In the presence of an effective chiral urea catalyst and a phosphoric acid additive, the intermolecular C-C bond formation between alkyl indoles and trifluoropyruvates proceeded with high efficiency and enantiocontrol. Unlike previous asymmetric C(sp3 -H) functionalizations of α-azaarenes, this process does not require the use of either a strong base or an electron-deficient substrate. The excellent enantiocontrol is particularly noteworthy in view of the severe background reaction as well as the complete inability of other types of catalysts evaluated. Control experiments, kinetic studies, and DFT calculations provided important insights into the mechanism.

Density functional theory calculations were carried out to study the reaction mechanisms of Ag(I)- and Zn(II)-catalyzed amination of unsaturated N-acylpyrazoles with azodicarboxylates. Our theoretical investigation focused on the origin of the metal-controlled regioselectivity (γ- versus α-amination). Through our calculations, it was found that the amination reactions occur via metal-dienolate intermediates, in which the Ag(I) center prefers to coordinate with the α-carbon or the pyrazolyl N-donor site of the dienolate ligand, while the Zn(II) center prefers to coordinate with the O-donor of the dienolate ligand. The different site preferences for coordination with dienolate between the Ag(I) and Zn(II) metal centers play the key roles in the different regioselectivity observed experimentally.

The long noncoding RNA (lncRNA) AWPPH, also termed microRNA-4435-2HG, has been associated with the poor prognosis of patients with hepatocellular carcinoma (HCC), and has been demonstrated to promote the progression of HCC and bladder cancer. The present study aimed to investigate the role of lncRNA AWPPH in glioma. The expression levels of AWPPH in tumor tissues obtained from patients with glioma and in plasma samples obtained from patients with glioma and healthy controls were detected by reverse transcription-quantitative polymerase chain reaction. The plasma levels of transforming growth factor (TGF)-β1 were measured by an enzyme-linked immunosorbent assay. An AWPPH expression vector was transfected into human glioma cell lines. Subsequently, cancer cell migration and invasion were assessed by Transwell migration and invasion assays, respectively. The expression of TGF-β1 in the transfected-glioma cells was detected by western blot analysis. It was identified that AWPPH expression levels in tumor tissues were higher in patients with metastatic glioma; however, no significant differences in AWPPH expression were revealed between patients with different tumor sizes. The plasma levels of AWPPH were positively correlated with the plasma levels of TGF-β1 in patients with glioma but not in healthy controls. In addition, AWPPH overexpression enhanced cancer cell migration and invasion, and upregulated TGF-β1 expression. Treatment with TGF-β1 demonstrated no significant effect on AWPPH expression; however, a TGF-β inhibitor attenuated the effects of AWPPH overexpression on cell migration and invasion. Therefore, the present study proposed that AWPPH may promote the migration and invasion of glioma cells by activating the TGF-β pathway.

DFT calculations have been carried out to study the mechanisms and origin of regioselectivity in Rh- and Ir-catalyzed hydroalkynylation of enamides with terminal alkynes. The two reactions, despite...

Treatment of osmacyclopentadiene derivatives 1 with phenyl or isopropyl isothiocyanate gave the fused five and six-membered osmacycles 2-5 by a formal [4+2] cyclization. The facile protonation of the newly generated exocyclic imine in complexes 2-5 afforded conjugation-extended osmacycle derivatives 6-9. Compounds 2-9 each contain two main-group heteroatoms (N and S) in the fused six-membered ring located at the ortho (for S) and para (for N) positions relative to the osmium centre; these species can be regarded as rare osma-1,3-thiazine derivatives and represent the first fused metallathiazine derivatives. In contrast to the non-planar organic 6H-1,3-thiazine, nearly coplanar metallathiazines 8 and 9 can be achieved by tuning the groups on the two nitrogen atoms. These unique metal-bridged osma-1,3-thiazine derivatives exhibit remarkable stabilities, broad spectral absorptions spanning the visible spectra, and considerable photothermal properties, which suggests their potential applications in material science.

Main group cluster compounds have attracted increasing attention in the past decades. Despite recent developments in their synthesis, the description of their electronic structures is usually limited to simply applying Wade's rule originally developed for borane compounds. This traditional approach is once again challenged by two recently reported group 14 metalloid clusters in the form of [Pd3Ge18R6]2-. In this work, we put forward a modular bonding model for these two clusters, via principal interacting orbital (PIO) analysis. The site preference for six substituents has also been analyzed.

The reactions of [RhCl(COD)]2 with a series of diazoalkanes with different substitutents were investigated. The outcomes of the reactions were found to be substituent-dependent via four different pathways. (1) The reactions with diazoindenes produced η5-cyclopentadienyl complexes. (2) The reaction with diazofluorene produced a mixture of olefin and azine compounds. (3) The reactions with monosubstituted diazoalkanes RCHN2 (R = Ph, MeO2C) produced olefins RCH═CHR. (4) The reaction with the disubstituted diazoalkane Ph2CN2 produced the azine Ph2C═N–N═CPh2 only. Computational studies have been carried out to understand the interesting substituent effect by comparing the kinetics and thermodynamics of the reaction pathways. It was found that the reactions with diazocyclopentadiene, diazoindene, and Ph2CN2 are kinetically controlled, while the reactions with RCHN2 and diazofluorene are both thermodynamically and kinetically controlled.

Chemical systems with open-shell electronic structure have been gaining attention these days. Their potential applications in first-row transition metal catalysis, molecular wires, photovoltaics and other potential applications have urged the adoption of a simple analysis tool to better understand their open-shell electronic structures, especially the role played by the unpaired electrons. Despite its lack of popularity, spin natural orbital (SNO) analysis is a tool we found to well-suit this purpose. We have therefore re-examined how the SNO could help us analyze some interesting open-shell systems, including mixed-valence compounds, singlet biradicals, and antiferromagnetically coupled systems. We found that some interesting patterns emerge from SNO analysis, especially those associated with exchange interaction. © 2019 Wiley Periodicals, Inc.

DFT calculations have been carried out to study the reaction mechanism of copper-catalyzed three-component boracarboxylation of alkene with CO2 and diboron. The competing reaction pathways involving two components have also been investigated for comparison. Through this theoretical study deep mechanistic insight on this multicomponent reaction is provided.

The mononuclear cyclic (alkyl)(amino)carbene (cAAC) supported titanium(iii) chloride complex [(cAAC)2TiCl3] has been synthesized by treatment of free cAAC with TiCl3(THF)3. Further reduction of (cAAC)2TiCl3 with potassium graphite (KC8) afforded the desired (cAAC)2TiCl2 complex, which features a small S-T energy gap. Both complexes were structurally characterized and represent the first cAAC supported Ti complexes.

Systematic bonding analysis has been carried out for transition metal complexes containing more than one redox-active/non-innocent ligand. These complexes include tetralithio spiroaromatic palladole, dicupra[10]annulene, highly reduced nickel cyclooctadiene complex and tris(dithiolene)vanadium(iv). Our detailed bonding analysis reveals a common inter-ligand delocalisation pattern in these cases.

The 4-coordinated RuII chalcogenolate complexes [Ru(STipp)2(PPh3)2] (Tipp = 2,4,6-triisopropylphenyl, 1) and [Ru(SeMes)2(PPh3)2] (Mes = 2,4,6-trimethylphenyl, 2) have been synthesized, and their reactions with PhICl2 and organic azides have been studied. Complex 2 synthesized from [RuII(PPh3)3Cl2] and NaSeMes displays a seesaw structure with P–Ru–P and Se–Ru–Se bond angles of 103.43(13) and 145.26(6)°, respectively. Natural bond order analyses revealed that in each of 1 and 2, there are two n → σ* (donor–acceptor) π interactions between the chalcogen lone pairs and the Ru–P antibonding molecular orbitals. The calculated second-order perturbation interaction energies of the two interactions for 1 (20.5 and 18.3 kcal mol−1) are stronger than those of 2 (13.6 and 11.0 kcal mol−1), suggesting the thiolate ligand (TippS−) is a stronger π-donor than the selenolate ligand (MesSe−) with respect to RuII. Chlorination of 1 with PhICl2 afforded the dichloride complex [Ru(STipp)2Cl2(PPh3)] (3), which was hydrolyzed to the hydroxo complex [Ru(STipp)2(OH)Cl(PPh3)] (4) after column chromatography on silica in air. Treatment of 4 with HCl and methyl triflate gave 3 and [Ru(STipp)2(OH)(OTf)(PPh3)] (OTf = triflate, 5), respectively. Reactions of 1 and 2 with p-tolyl azide (p-tolN3) afforded the tetrazene complexes [Ru{N4(p-tol)2}(ER)2(PPh3)] (ER = STipp (6), SeMes (7)), whereas that with tosyl azide (TsN3) gave the imido complexes [Ru(κ2-NTs)(STipp)2(PPh3)] (ER = STipp (8), SeMes (10)). The short Ru–Nimido distances in 8 [1.883(3) A] and 10 [1.892(2) A] are indicative of multiple bond character. Treatment of 8 with TsN3 afforded the tetrazene complex [Ru(N4Ts2)(STipp)2(PPh3)] (9), but no cycloaddition was found between 10 and TsN3. Nucleophilic attack of the imido ligand in 10 with methyl triflate yielded the amido complex [Ru(κ2-NMeTs)(SeMes)2(PPh3)](OTf) (11). The crystal structures of 2, 4, 6, and 8–11 have been determined.

Transition metal-free direct and base-catalyzed 1,2-diborations of arylacetylenes using pinB-BMes2 provided a syn/anti-isomeric mixture of diborylalkenes. The kinetic analysis showed that the reaction rate and isomer ratio were affected by reaction conditions and substituents on the aryl ring. DFT calculations indicated that direct addition proceeded via the interaction of acetylene-π with the BMes2 fragment. In contrast, for the base-catalyzed diboration, the previously isolated sp2–sp3 diborane and borataallene were confirmed as stable intermediates by calculations. The whole reaction pathways can be divided into the Bpin-migration and deprotonation steps, where the borataallene should be considered as a common intermediate. It should be noted that the deprotonation step is reversible and affords the kinetically less favoured isomer under the thermodynamic conditions. As a result, the composition of isomeric products, in the base-catalyzed diboration, is attributed to the small difference of activation barriers between direct and base-catalyzed systems., Combination of kinetic and DFT studies revealed a subtle balance for substituent effect toward the regioselectivity of the product in metal-free and base-catalyzed diboration of arylacetylenes.

The three-dimensional inorganic analogues of 9,10-diboraanthracene, B2X2(C2B10H10)2 (X = Cl, 1; X = Br, 2), were attained by salt elimination of Li2C2B10H10 and trihaloboranes. The methyl- and phenyl-substituted compounds B2Me2(C2B10H10)2 (3) and B2Ph2(C2B10H10)2 (4) were obtained by treating 1 or 2 with the corresponding Grignard reagents. These compounds were fully characterized by NMR, cyclic voltammetry (CV), IR, and single-crystal X-ray diffraction analyses. Experimental (CV and Gutmann-Beckett method) and computational (fluoride ion affinity, hydride ion affinity and LUMO energy) results suggest that the order of Lewis acidity is 2 > 1 > 4 > 3 > SbF5. Treatment of 1 or 2 with HSiEt3 gave a rare neutral borane-silane adduct, (Et3SiH)2B2H2(C2B10H10)2 (5). The equilibrium of 5 in solution was thoroughly investigated by spectroscopy and quantum calculations.

gem-Difluoroalkene is a bioisostere of carbonyl group for improving bioavailability of drug candidates. Herein we develop structurally diverse 2,2-difluorovinyl benzoates (BzO-DFs) as versatile building blocks for modular synthesis of gem-difluoroenol ethers (44 examples) and gem-difluoroalkenes (2 examples) by Ni-catalyzed cross coupling reactions. Diverse BzO-DFs derivatives bearing sensitive functional groups (e.g., C = C, TMS, strained carbocycles) are readily prepared from their bromodifluoroacetates and bromodifluoroketones precursors using metallic zinc as reductant. With Ni(COD)2 and dppf [1,1’-bis(diphenylphosphino)ferrocene] as catalyst, reactions of BzO-DFs with arylboronic acids and arylmagnesium/alkylzinc reagents afforded the desired gem-difluoroenol ethers and gem-difluoroalkenes in good yields. The Ni-catalyzed coupling reactions features highly regioselective C(vinyl)–O(benzoate) bond activation of the BzO-DFs. Results from control experiments and DFT calculations are consistent with a mechanism involving initial oxidative addition of the BzO-DFs by the Ni(0) complex. By virtue of diversity of the BzO-DFs and excellent functional group tolerance, this method is amenable to late-stage functionalization of multifunctionalized bioactive molecules., The gem-difluoroalkene functionality is relevant to drug design as it is a bioisostere of a carbonyl group. Here, the authors report the synthesis of 2,2-difluorovinyl benzoates as versatile building blocks for modular synthesis of gem-difluoroenol ethers and gem-difluoroalkenes by nickel-catalyzed cross coupling.

Clusters of group 14 elements show plenty of similarities with borane clusters. As such, chemists often try to understand their structure and bonding on the basis of Wade’s rules to predict and classify various clusters. Such practice, albeit very common, often faces challenges and difficulties due to significant differences in the bonding abilities between group 13 and 14 atoms, as well as the changes in the ionization energies and radial characteristics of atomic orbitals as the groups are descended. In this chapter, we have extensively discussed the structure and bonding of a wide variety of group 14 clusters, including bare clusters, substituent-decorated clusters, endohedral clusters, transition metal doped clusters, and their combinations. By thoroughly analyzing their electronic structures within the framework of molecular orbital theory, we have summarized their bonding patterns and explored the factors that affect the applicability of Wade’s rules in various group 14 clusters.

Asymmetric radical azidation for the synthesis of chiral alkylazides remains a tremendous challenge in organic synthesis. We report here an unprecedented highly enantioselective radical azidation of acrylamides catalyzed by 1 mol% of copper catalyst, and arrays of acrylamides were converted to the corresponding alkylazides in high yield with good to excellent enantioselectivities. Notably, employing anionic cyano-bisoxazoline (CN-Box) ligand is crucial, which generates a monomeric Cu(II) azide species, rather than a dimeric Cu(II) azide intermediate, for this highly enantioselective radical azidation.