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Inorganic Chemistry Aug 2021The mechanism of the aluminum-mediated hydroboration of terminal alkynes was investigated using a series of novel aluminum amidinate hydride and alkyl complexes bearing...
The mechanism of the aluminum-mediated hydroboration of terminal alkynes was investigated using a series of novel aluminum amidinate hydride and alkyl complexes bearing symmetric and asymmetric ligands. The new aluminum complexes were fully characterized and found to facilitate the formation of the ()-vinylboronate hydroboration product, with rates and orders of reaction linked to complex size and stability. Kinetic analysis and stoichiometric reactions were used to elucidate the mechanism, which we propose to proceed via the initial formation of an Al-borane adduct. Additionally, the most unstable complex was found to promote decomposition of the pinacolborane substrate to borane (BH), which can then proceed to catalyze the reaction. This mechanism is in contrast to previously reported aluminum hydride-catalyzed hydroboration reactions, which are proposed to proceed via the initial formation of an aluminum acetylide, or by hydroalumination to form a vinylboronate ester as the first step in the catalytic cycle.
PubMed: 34270214
DOI: 10.1021/acs.inorgchem.1c00619 -
Organic Letters Nov 2019Aminonucleosides are used as key motifs in medicinal and bioconjugate chemistry; however, existing strategies toward 3'-hypernucleophilic amine systems do not readily...
Aminonucleosides are used as key motifs in medicinal and bioconjugate chemistry; however, existing strategies toward 3'-hypernucleophilic amine systems do not readily deliver -configured products. We report diastereoselective syntheses of - and -configured 3'-hydroxyamino- and 3'-methoxyamino-nucelosides from 3'-imine intermediates. The presence or absence of the 5'-hydroxyl-group protection dictates facial selectivity via inter- or intramolecular delivery of hydride from BH (borane). Protecting group screening gave one access to previously unknown 3'-methoxyamino-deoxyguanosine derivatives.
PubMed: 31668079
DOI: 10.1021/acs.orglett.9b03474 -
Chemical Society Reviews Nov 2021The self-assembly of inorganic nanoparticles to larger structures is of great research interest as it allows the fabrication of novel materials with collective... (Review)
Review
The self-assembly of inorganic nanoparticles to larger structures is of great research interest as it allows the fabrication of novel materials with collective properties correlated to the nanoparticles' individual characteristics. Recently developed methods for controlling nanoparticle organisation have enabled the fabrication of a range of new materials. Amongst these, the assembly of nanoparticles using DNA has attracted significant attention due to the highly selective recognition between complementary DNA strands, DNA nanostructure versatility, and ease of DNA chemical modification. In this review we discuss the application of various chemical DNA modifications and molecular intercalators as tools for the manipulation of DNA-nanoparticle structures. In detail, we discuss how DNA modifications and small molecule intercalators have been employed in the chemical and photochemical DNA ligation in nanostructures; DNA rotaxanes and catenanes associated with reconfigurable nanoparticle assemblies; and DNA backbone modifications including locked nucleic acids, peptide nucleic acids and borane nucleic acids, which affect the stability of nanostructures in complex environments. We conclude by highlighting the importance of maximising the synergy between the communities of DNA chemistry and nanoparticle self-assembly with the aim to enrich the library of tools available for the manipulation of nanostructures.
Topics: DNA; Intercalating Agents; Nanoparticles; Nanostructures; Nucleic Acids
PubMed: 34792047
DOI: 10.1039/d1cs00632k -
Molecules (Basel, Switzerland) Nov 2022In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl] (Cp* = -CMe) with four...
In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl] (Cp* = -CMe) with four equivalents of Li[BHE] (E = Se or S). In the case of the heavier chalcogen (Se), the reaction led to the isolation of the tri-niobium cubane-like cluster [(NbCp*)(-Se)(BH)(-Se)] () and the homocubane-like cluster [(NbCp*)(-Se)(-Se)(BH)(-Se)] (). Interestingly, the tri-niobium framework of stabilizes a selenaborate {SeBH} ligand. A selenium atom is further introduced between boron and one of the selenium atoms of to yield cluster . On the other hand, the reaction with the sulfur-containing borate adduct [LiBHS] afforded the trimetallic clusters [(NbCp*)(-S){-S(BH)}] () and [(NbCp*)(-S){-S(S)}] (). Both clusters and have an NbS core, which further stabilizes {BH} and mono-sulfur units, respectively, through bi-chalcogen coordination. All of these species were characterized by B{H}, H, and C{H} NMR spectroscopy, mass spectrometry, infrared (IR) spectroscopy, and single-crystal X-ray crystallography. Moreover, theoretical investigations revealed that the triangular Nb framework is aromatic in nature and plays a vital role in the stabilization of the borate, borane, and chalcogen units.
Topics: Borates; Selenium; Organometallic Compounds; Models, Molecular; Niobium; Boron; Sulfur
PubMed: 36364299
DOI: 10.3390/molecules27217473 -
ACS Catalysis Jan 2022Reactive carbenes generated from diazo compounds are key intermediates for a range of organic reactions to afford synthetically useful organic compounds. The majority of... (Review)
Review
Reactive carbenes generated from diazo compounds are key intermediates for a range of organic reactions to afford synthetically useful organic compounds. The majority of these reactions have been carried out using transition metal catalysts. However, the formation of carbene intermediates using main group elements has not been widely investigated for synthetic purposes. Recent studies have demonstrated that triarylboranes can be used for the generation of reactive carbene intermediates in both stoichiometric and catalytic reactions. These new reactivities of triarylboranes have gained significant attention in synthetic chemistry particularly in catalytic studies. The range of organic compounds that have been synthesized through these reactions are important as pharmaceuticals or agrochemicals. In this perspective, we highlight the recent progress and ongoing challenges of carbene transfer reactions generated from their corresponding diazo precursors using triarylboranes as catalysts. We also highlight the stoichiometric use of triarylboranes in which the boranes not only activate the diazo functionality to afford a carbene intermediate but also actively participate in the reactions as a reagent. The different mechanisms for activation and carbene transfer are described along with the mechanistic and computational studies that have aided the elucidation of these reaction pathways. Potential opportunities for the use of boranes as a catalyst toward different carbene transfer reactions and their future prospects are discussed.
PubMed: 35028191
DOI: 10.1021/acscatal.1c04746 -
Yakugaku Zasshi : Journal of the... 2021The interaction between transition metals and ligands is important for catalytic reactions. The ligands are largely dominated by the covalent X-type (hydride, alkyl and... (Review)
Review
The interaction between transition metals and ligands is important for catalytic reactions. The ligands are largely dominated by the covalent X-type (hydride, alkyl and halogen) and/or dative L-type ligands (e.g., P, N, CO, olefin, etc.). Therefore, the interaction of the Z-type ligands (B, Al and Si, etc.) with transition metals is emerging as a new concept for the reactivity of the metal center. Recently, we developed the synthesis of the gold complex Au(DPB)X (DPB=diphosphine-borane) featuring the Z-type ligand, and their catalytic reaction. The gold catalysts showed a high activity compared to the general catalysts (without Z-ligand) for the various cyclization reactions due to the electron-withdrawing effect of the Z-ligand on the coordinating gold center. In this review, first the structure analysis of the synthesized Au→Z complex is introduced in detail, and second, the catalytic reactions based on the alkyne activation are described.
Topics: Alkynes; Catalysis; Cyclization; Electrons; Gold; Gold Compounds; Ligands; Molecular Structure
PubMed: 33642496
DOI: 10.1248/yakushi.20-00179-1 -
Angewandte Chemie (International Ed. in... Nov 2022The synthesis of tris(ortho-carboranyl)borane (BoCb ), a single site neutral Lewis superacid, in one pot from commercially available materials is achieved. The high...
The synthesis of tris(ortho-carboranyl)borane (BoCb ), a single site neutral Lewis superacid, in one pot from commercially available materials is achieved. The high fluoride ion affinity (FIA) confirms its classification as a Lewis superacid and the Gutmann-Beckett method as well as adducts with Lewis bases indicate stronger Lewis acidity over the widely used fluorinated aryl boranes. The electron withdrawing effect of ortho-carborane and lack of pi-delocalization of the LUMO rationalize the unusually high Lewis acidity. Catalytic studies indicate that BoCb is a superior catalyst for promoting C-F bond functionalization reactions than tris(pentafluorophenyl)borane [B(C F ) ].
PubMed: 36135949
DOI: 10.1002/anie.202212073 -
Journal of Pharmaceutical Sciences Jan 2020Diphtheria toxoid is produced by detoxification of diphtheria toxin with formaldehyde. This study was performed to elucidate the chemical nature and location of...
Diphtheria toxoid is produced by detoxification of diphtheria toxin with formaldehyde. This study was performed to elucidate the chemical nature and location of formaldehyde-induced modifications in diphtheria toxoid. Diphtheria toxin was chemically modified using 4 different reactions with the following reagents: (1) formaldehyde and NaCNBH, (2) formaldehyde, (3) formaldehyde and NaCNBH followed by formaldehyde and glycine, and (4) formaldehyde and glycine. The modifications were studied by SDS-PAGE, primary amino group determination, and liquid chromatography-electrospray mass spectrometry of chymotryptic digests. Reaction 1 resulted in quantitative dimethylation of all lysine residues. Reaction 2 caused intramolecular cross-links, including the NAD-binding cavity and the receptor-binding site. Moreover, A fragments and B fragments were cross-linked by formaldehyde on part of the diphtheria toxoid molecules. Reaction 3 resulted in formaldehyde-glycine attachments, including in shielded areas of the protein. The detoxification reaction typically used for vaccine preparation (reaction 4) resulted in a combination of intramolecular cross-links and formaldehyde-glycine attachments. Both the NAD-binding cavity and the receptor-binding site of diphtheria toxin were chemically modified. Although CD4 T-cell epitopes were affected to some extent, one universal CD4 T-cell epitope remained almost completely unaltered by the treatment with formaldehyde and glycine.
Topics: Borohydrides; Chromatography, Reverse-Phase; Diphtheria Toxin; Diphtheria Toxoid; Drug Compounding; Electrophoresis, Polyacrylamide Gel; Epitopes, T-Lymphocyte; Formaldehyde; Glycine; Models, Molecular; Protein Conformation; Spectrometry, Mass, Electrospray Ionization; Structure-Activity Relationship
PubMed: 31678246
DOI: 10.1016/j.xphs.2019.10.047 -
Chemical Science Jan 2022An unprecedented redox-neutral annulation reaction of tertiary anilines with electron-deficient alkynes was developed that proceeds through a cascade Friedel-Crafts...
An unprecedented redox-neutral annulation reaction of tertiary anilines with electron-deficient alkynes was developed that proceeds through a cascade Friedel-Crafts alkylation/[1,5]-hydride transfer/Mannich cyclization sequence. Under B(CF) catalysis, a range of functionalized 1,2,3,4-tetrahydroquinolines were facilely constructed in moderate to good yields with exclusive 3,4--stereochemistry. The commercial availability of the catalyst and the high atom and step economy of the procedure, together with metal-free and external oxidant-free conditions, make this an attractive method in organic synthesis.
PubMed: 35173942
DOI: 10.1039/d1sc05629h -
Inorganic Chemistry Oct 2023A series of -substituted acenaphthene-based phosphine selenoether bidentate ligands Acenap(PrP)(SeAr) (-, Acenap = acenaphthene-5,6-diyl, Ar = Ph, mesityl,...
A series of -substituted acenaphthene-based phosphine selenoether bidentate ligands Acenap(PrP)(SeAr) (-, Acenap = acenaphthene-5,6-diyl, Ar = Ph, mesityl, 2,4,6-trisopropylphenyl and supermesityl) were prepared. The rigid acenaphthene framework induces a forced overlap of the phosphine and selenoether lone pairs, resulting in a large magnitude of through-space coupling, ranging from 452 to 545 Hz. These rigid ligands - were used to prepare a series of selected late d-block metals, mercury, and borane complexes, which were characterized, including by multinuclear NMR and single-crystal X-ray diffraction. The Lewis acidic motifs (BH, Mo(CO), Ag, PdCl, PtCl, and HgCl) bridge the two donor atoms (P and Se) in all but one case in the solid-state structures. Where the bridging motif contained NMR-active nuclei (B, Ag, Ag, Pt, and Hg), and couplings are observed directly, in addition to the altered in the respective NMR spectra. The solution NMR data are correlated with single-crystal diffraction data, and in the case of mercury(II) complexes, they are also correlated with the solid-state NMR data and coupling deformation density calculations. The latter indicate that the through-space interaction dominates in free , while in the complex, the main coupling pathway is via the metal atom and not through the carbon framework of the acenaphthene ring system.
PubMed: 37722079
DOI: 10.1021/acs.inorgchem.3c02255