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Angewandte Chemie (International Ed. in... Sep 2021Structurally authenticated free B-alkyl boroles are presented and electronic implications of alkyl substitution were assessed. Deprotonation of a boron-bound exocyclic...
Structurally authenticated free B-alkyl boroles are presented and electronic implications of alkyl substitution were assessed. Deprotonation of a boron-bound exocyclic methyl group in a B-methyl borole yields the first 5-boratafulvene anion-an isomer to boratabenzene. Boratafulvene was structurally characterized and its electronic structure probed by DFT calculations. The pK value of the exocyclic B-CH in a set of boroles was computationally approximated and confirmed a pronounced acidic character caused by the boron atom embedded in an anti-aromatic moiety. The non-aromatic boratafulvene reacts as a C-centered nucleophile with the mild electrophile Me SnCl to give a stannylmethyl borole, regenerating the anti-aromaticity. As nucleophilic synthons for boroles, boratafulvenes thus open an entirely new avenue for synthetic strategies toward this highly reactive class of heterocycles. Boratafulvene reacts as a methylene transfer reagent in a bora-Wittig-type reaction generating a borole oxide.
PubMed: 34196471
DOI: 10.1002/anie.202107968 -
Molecules (Basel, Switzerland) Jan 2023The development and application of new organoboron reagents as Lewis acids in synthesis and metal-free catalysis have dramatically expanded over the past 20 years. In... (Review)
Review
The development and application of new organoboron reagents as Lewis acids in synthesis and metal-free catalysis have dramatically expanded over the past 20 years. In this context, we will show the recent uses of the simple and relatively weak Lewis acid BPh-discovered 100 years ago-as a metal-free catalyst for various organic transformations. The first part will highlight catalytic applications in polymer synthesis such as the copolymerization of epoxides with CO, isocyanate, and organic anhydrides to various polycarbonate copolymers and controlled diblock copolymers as well as alternating polyurethanes. This is followed by a discussion of BPh as a Lewis acid component in the frustrated Lewis pair (FLP) mediated cleavage of hydrogen and hydrogenation catalysis. In addition, BPh-catalyzed reductive N-methylations and C-methylations with CO and silane to value-added organic products will be covered as well along with BPh-catalyzed cycloadditions and insertion reactions. Collectively, this mini-review showcases the underexplored potential of commercially available BPh in metal-free catalysis.
PubMed: 36771006
DOI: 10.3390/molecules28031340 -
ChemMedChem May 2021"There's plenty of room at the bottom" (Richard Feynman, 1959): an invitation for (metalla)carboranes to enter the (new) field of nanomedicine. For two decades, the... (Review)
Review
"There's plenty of room at the bottom" (Richard Feynman, 1959): an invitation for (metalla)carboranes to enter the (new) field of nanomedicine. For two decades, the number of publications on boron cluster compounds designed for potential applications in medicine has been constantly increasing. Hundreds of compounds have been screened in vitro or in vivo for a variety of biological activities (chemotherapeutics, radiotherapeutics, antiviral, etc.), and some have shown rather promising potential for further development. However, until now, no boron cluster compounds have made it to the clinic, and even clinical trials have been very sparse. This review introduces a new perspective in the field of medicinal boron chemistry, namely that boron-based drugs should be regarded as nanomedicine platforms, due to their peculiar self-assembly behaviour in aqueous solutions, and treated as such. Examples for boron-based 12- and 11-vertex clusters and appropriate comparative studies from medicinal (in)organic chemistry and nanomedicine, highlighting similarities, differences and gaps in physicochemical and biological characterisation methods, are provided to encourage medicinal boron chemists to fill in the gaps between chemistry laboratory and real applications in living systems by employing bioanalytical and biophysical methods for characterising and controlling the aggregation behaviour of the clusters in solution.
Topics: Boranes; Chemistry, Pharmaceutical; Nanomedicine
PubMed: 33507635
DOI: 10.1002/cmdc.202000983 -
Nature Communications Jan 2021Although various methods have been developed for sequencing cytosine modifications, it is still challenging for specific and quantitative sequencing of individual...
Although various methods have been developed for sequencing cytosine modifications, it is still challenging for specific and quantitative sequencing of individual modification at base-resolution. For example, to obtain both true 5-methylcytosine (5mC) and true 5-hydroxymethylcytosine (5hmC) information, the two major epigenetic modifications, it usually requires subtraction of two methods, which increases noise and requires high sequencing depth. Recently, we developed TET-assisted pyridine borane sequencing (TAPS) for bisulfite-free direct sequencing of 5mC and 5hmC. Here we demonstrate that two sister methods, TAPSβ and chemical-assisted pyridine borane sequencing (CAPS), can be effectively used for subtraction-free and specific whole-genome sequencing of 5mC and 5hmC, respectively. We also demonstrate pyridine borane sequencing (PS) for whole-genome profiling of 5-formylcytosine and 5-carboxylcytosine, the further oxidized derivatives of 5mC and 5hmC. This work completes the set of versatile borane reduction chemistry-based methods as a comprehensive toolkit for direct and quantitative sequencing of all four cytosine epigenetic modifications.
Topics: 5-Methylcytosine; Animals; Base Sequence; Mice; Mouse Embryonic Stem Cells; Oxidation-Reduction; Pyridines; Sequence Analysis, DNA; Sulfites
PubMed: 33504799
DOI: 10.1038/s41467-021-20920-2 -
Chemistry (Weinheim An Der Bergstrasse,... Nov 2020Metalation of secondary diaminophosphine boranes by alkali metal amides provides a robust and selective access route to a range of metal diaminophosphide boranes M[(R N)...
Metalation of secondary diaminophosphine boranes by alkali metal amides provides a robust and selective access route to a range of metal diaminophosphide boranes M[(R N) P(BH )] (M=Li, Na, K; R=alkyl, aryl) with acyclic or heterocyclic molecular backbones, whereas reduction of a chlorodiaminophosphine borane gave less satisfactory results. The metalated species were characterized in situ by NMR spectroscopy and in two cases isolated as crystalline solids. Single-crystal XRD studies revealed the presence of salt-like structures with strongly interacting ions. Synthetic applications of K[(R N) P(BH )] were studied in reactions with a 1,2-dichlorodisilane and CS , which afforded either mono- or difunctional phosphine boranes with a rare combination of electronegative amino and electropositive functional disilanyl groups on phosphorus, or a phosphinodithioformate. Spectroscopic studies gave a first hint that removal of the borane fragment may be feasible.
PubMed: 32567741
DOI: 10.1002/chem.202002296 -
Chemical Science Jul 2020Selective defunctionalisation of organic molecules to valuable intermediates is a fundamentally important transformation in organic synthesis. Despite the advances made... (Review)
Review
Selective defunctionalisation of organic molecules to valuable intermediates is a fundamentally important transformation in organic synthesis. Despite the advances made in efficient and selective defunctionalisation using transition-metal catalysis, the cost, toxicity, and non-renewable properties limit its application in industrial manufacturing processes. In this regard, boron Lewis acid catalysis has emerged as a powerful tool for the cleavage of carbon-heteroatom bonds. The ground-breaking finding is that the strong boron Lewis acid B(CF) can activate Si-H bonds through η coordination, and this Lewis adduct is a key intermediate that enables various reduction processes. This system can be tuned by variation of the electronic and structural properties of the borane catalyst, and together with different hydride sources high chemoselectivity can be achieved. This Perspective provides a comprehensive summary of various defunctionalisation reactions such as deoxygenation, decarbonylation, desulfurisation, deamination, and dehalogenation, all of which catalysed by boron Lewis acids.
PubMed: 34094457
DOI: 10.1039/d0sc03712e -
Angewandte Chemie (International Ed. in... May 2022Carboranes are boron-carbon molecular clusters that possess unique properties, such as their icosahedron geometry, high boron content, and delocalized three-dimensional... (Review)
Review
Carboranes are boron-carbon molecular clusters that possess unique properties, such as their icosahedron geometry, high boron content, and delocalized three-dimensional aromaticity. These features render carboranes valuable building blocks for applications in supramolecular design, nanomaterials, optoelectronics, organometallic coordination chemistry, and as boron neutron capture therapy (BNCT) agents. Despite tremendous progress in this field, stoichiometric chemical redox reagents are largely required for the oxidative activation of carborane cages. In this context, electrosyntheses represent an alternative strategy for more sustainable molecular syntheses. It is only in recent few years that considerable progress has been made in electrochemical cage functionalization of carboranes, which are summarized in this Minireview. We anticipate that electrocatalysis will serve as an increasingly powerful stimulus within the current renaissance of carborane electrochemistry.
Topics: Boranes; Boron; Carbon
PubMed: 35148009
DOI: 10.1002/anie.202200323 -
Chemical Reviews Mar 2022The number of rare earth (RE) starting materials used in synthesis is staggering, ranging from simple binary metal-halide salts to borohydrides and "designer reagents"... (Review)
Review
The number of rare earth (RE) starting materials used in synthesis is staggering, ranging from simple binary metal-halide salts to borohydrides and "designer reagents" such as alkyl and organoaluminate complexes. This review collates the most important starting materials used in RE synthetic chemistry, including essential information on their preparations and uses in modern synthetic methodologies. The review is divided by starting material category and supporting ligands (, metals as synthetic precursors, halides, borohydrides, nitrogen donors, oxygen donors, triflates, and organometallic reagents), and in each section relevant synthetic methodologies and applications are discussed.
Topics: Borohydrides; Ligands; Metals; Metals, Rare Earth
PubMed: 35099940
DOI: 10.1021/acs.chemrev.1c00842 -
Chemistry (Weinheim An Der Bergstrasse,... Jun 2022Herein, the synthesis and characterization of the carbene-stabilized boryl phosphinidenes 1-3 are reported. Compounds 1-3 are obtained by reacting Me-cAAC=PK (Me...
Herein, the synthesis and characterization of the carbene-stabilized boryl phosphinidenes 1-3 are reported. Compounds 1-3 are obtained by reacting Me-cAAC=PK (Me -cAAC=dimethyl cyclic(alkyl)(amino)carbene) and dihaloaryl borane in toluene. All three compounds were characterized by X-ray crystallography. Quantum mechanical studies indicated that these compounds have two lone pairs on the P center viz., an σ-type lone pair and a "hidden" π-type lone pair. Hence, these compounds can act as double Lewis bases, and the basicity of the π-type lone pair is higher than the σ-type lone pair.
PubMed: 35357049
DOI: 10.1002/chem.202200913 -
Postepy Biochemii Jun 2022Nucleoside boranephosphonates are nucleotide analogues in which one of the non-bridging oxygen atom of the phosphate part has been replaced by a borane group (-BH3).... (Review)
Review
Nucleoside boranephosphonates are nucleotide analogues in which one of the non-bridging oxygen atom of the phosphate part has been replaced by a borane group (-BH3). This modification imparts a wide spectrum of biological activity, e.g., activation of ribonuclease H, resistance to endo- and exonucleases, and their respective triphosphates are good substrates for DNA and RNA polymerases. Nucleoside boranephosphonate derivatives are used in antisense therapy, silencing gene expression using siRNA strategies, and as potential antiviral and anti-cancer prodrugs. Boranephosphonates find also applications as aptamers and as substrates in a new method of DNA sequencing. This review briefly presents potential biological applications of nucleoside boranephosphonates.
Topics: Antiviral Agents; DNA; Nucleosides; Nucleotides; Sequence Analysis, DNA
PubMed: 35792645
DOI: 10.18388/pb.2021_425