Transition-metal-like coordination chemistry of dicoordinate borylenes with organic azides.

The photolytic or oxidative liberation of a cyclic (amino)(alkyl)carbene (CAAC)-stabilized arylborylene in the presence of organoazides yielded borylene-organoazide complexes (4a,b) has been achieved in a manner akin to the first step of the Staudinger reaction. Similarly, a CAAC-stabilized aminoborylene also afforded borylene-organoazide complexes (6a-c), which further undergo rearrangement to produce aminoborane triazene species (7a,b).

Hydrosilylation of BB triple bonds: catalyst- and reductant-free construction of B-Si bonds and BSi heterocycles.

Hydrosilanes undergo mild, uncatalyzed single and double 1,2-addition across the B-B triple bonds of diborynes, leading to an unsymmetrical silyldiborene and compounds with novel non-cluster three-membered BSi rings. The reactions are a new addition to the very few catalyst- and alkali-metal-free methods available for the construction of B-Si bonds.

Stepwise and selective synthesis of chelating, multimetallic and mixed-metal π-diborene complexes.

The reaction of a pyridyl-substituted, doubly Lewis base-stabilised diborene with different amounts of copper(I) precursors led to the formation of the first chelating π-diborene complexes, the first π-diborene complexes in which metals are bound to both faces of the BB bond, and the first mixed-metal π-diborene species.

The effect of inflammation, SARS-CoV-2 infection, age and mental health on serotonin, and kynurenine and catecholamine pathway metabolites.

Background: A high prevalence of mental disorders following COVID-19 has been described. It is therefore essential to elucidate underlying biological mechanisms linking SARS-CoV-2 infection and mental health. The kynurenine and catecholamine metabolic pathways are modulated by inflammation and can affect systemic levels of serotonin and dopamine.

Metal-Free Intermolecular C-H Borylation of N-Heterocycles at B-B Multiple Bonds.

Carbene-stabilized diborynes of the form LBBL (L=N-heterocyclic carbene (NHC) or cyclic alkyl(amino)carbene (CAAC)) induce rapid, high yielding, intermolecular ortho-C-H borylation at N-heterocycles at room temperature. A simple pyridyldiborene is formed when an NHC-stabilized diboryne is combined with pyridine, while a CAAC-stabilized diboryne leads to activation of two pyridine molecules to give a tricyclic alkylideneborane, which can be forced to undergo a further H-shift resulting in a zwitterionic, doubly benzo-fused 1,3,2,5-diazadiborinine by heating. Use of the extended N-heteroaromatic quinoline leads to a borylmethyleneborane under mild conditions via an unprecedented boron-carbon exchange process.

The proarrhythmic effects of hypothermia in atria isolated from 5-HT-receptor-overexpressing mice.

We investigated whether hypothermia would be arrhythmogenic in mice that overexpress the human 5-HT receptor only in their cardiac myocytes (5-HT-TG). Contractile studies were performed in isolated, electrically driven (1 Hz) left and spontaneously beating right atrial preparations of 5-HT-TG and littermate wild-type control mice (WT). Hypothermia (23 °C) decreased the force of contraction in the mouse right and left atrial preparations.

Rethinking Borole Cycloaddition Reactivity.

Boroles are attracting broad interest for their myriad and diverse applications, including in synthesis, small molecule activation and functional materials. Their properties and reactivity are closely linked to the cyclic conjugated diene system, which has been shown to participate in cycloaddition reactions, such as the Diels-Alder reaction with alkynes. The reaction steps leading to boranorbornadienes, borepins and tricyclic boracyclohexenes from the thermal reaction of boroles with alkynes are seemingly well understood as judged from the literature.

Isolation of Neutral, Mono-, and Dicationic B P Rings by Diphosphorus Addition to a Boron-Boron Triple Bond.

The NHC-stabilised diboryne (B (SIDep) ; SIDep=1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene) undergoes a high-yielding P-P bond activation with tetraethyldiphosphine at room temperature to form a B P heterocycle via a diphosphoryldiborene by 1,2-diphosphination. The heterocycle can be oxidised to a radical cation and a dication, respectively, depending on the oxidant used and its counterion. Starting from the planar, neutral 1,3-bis(alkylidene)-1,3-diborata-2,4-diphosphoniocyclobutane, each oxidation step leads to decreased B-B distances and loss of planarity by cationisation.

Highly Colored Boron-Doped Thiazolothiazoles from the Reductive Dimerization of Boron Isothiocyanates.

Reduction of (CAAC)BBr (NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z-isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)-stabilized, boron-doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates.

Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron-Boron Triple Bond.

An N-heterocyclic-carbene-stabilized diboryne undergoes rapid, high-yielding and catalyst-free hydroamination reactions with primary amines, yielding 1-amino-2-hydrodiborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron-rich anilines, a second hydroamination can occur at the diborene to generate 1,1-diamino-2,2-dihydrodiboranes.

Hydrophosphination of boron-boron multiple bonds.

Five compounds containing boron-boron multiple bonds are shown to undergo hydrophosphination reactions with diphenylphosphine in the absence of a catalyst. With diborenes, the products obtained are highly dependent on the substitution pattern at the boron atoms, with both 1,1- and 1,2-hydrophosphinations observed. With a symmetrical diboryne, 1,2-hydrophosphination yields a hydro(phosphino)diborene.

Mild synthesis of diboryldiborenes by diboration of B-B triple bonds.

A set of diboryldiborenes are prepared by the mild, catalyst-free, room-temperature diboration of the B-B triple bonds of doubly base-stabilized diborynes. Two of the product diboryldiborenes are found to be air- and water-stable in the solid state, an effect that is attributed to their high crystallinity and extreme insolubility in a wide range of solvents.

Single and Double Hydroboration of B-B Triple Bonds and Convergent Routes to a Cationic Tetraborane.

A compound with a boron-boron triple bond is shown to undergo stepwise hydroboration reactions with catecholborane to yield an unsymmetrical hydro(boryl)diborene and a 2,3-dihydrotetraborane. Abstraction of H from the latter compound produces an unusual cationic, planar tetraborane with a hydrogen atom bridging the central B moiety. Spectroscopic and crystallographic data and DFT calculations support a "protonated diborene" structure for this compound, which can also be accessed via direct protonation of the corresponding diborene.

Synthesis of fused B,N-heterocycles by alkyne cleavage, NHC ring-expansion and C-H activation at a diboryne.

The addition of alkynes to a saturated N-heterocyclic carbene (NHC)-supported diboryne results in spontaneous cycloaddition, with complete B[triple bond, length as m-dash]B and C[triple bond, length as m-dash]C triple bond cleavage, NHC ring-expansion and activation of a variety of C-H bonds, leading to the formation of complex mixtures of fused B,N-heterocycles.

Single and double activation of acetone by isolobal B[triple bond, length as m-dash]N and B[triple bond, length as m-dash]B triple bonds.

B[triple bond, length as m-dash]N and B[triple bond, length as m-dash]B triple bonds induce C-H activation of acetone to yield a (2-propenyloxy)aminoborane and an unsymmetrical 1-(2-propenyloxy)-2-hydrodiborene, respectively. DFT calculations showed that, despite their stark electronic differences, both the B[triple bond, length as m-dash]N and B[triple bond, length as m-dash]B triple bonds activate acetone a similar coordination-deprotonation mechanism. In contrast, the reaction of acetone with a cAAC-supported diboracumulene yielded a unique 1,2,3-oxadiborole, which according to DFT calculations also proceeds an unsymmetrical diborene, followed by intramolecular hydride migration and a second C-H activation of the enolate ligand.

Reaction of Dihalodiboranes(4) with a N-Heterocyclic Silylene: Facile Construction of 1-Aryl-2-Silyl-1,2-Diboraindanes.

Dihalodiboranes(4) react with a N-heterocyclic silylene (NHSi) to generate NHSi adducts of 1-aryl-2-silyl-1,2-diboraindanes, as was confirmed by X-ray crystallography, featuring the functionalization of both B-X (X=halogen) bonds and a sp - or sp -C-H bond under mild conditions. Coordination of a third NHSi to the proposed 1,1-diaryl-2,2-disilyldiborane(4) intermediates, generated by a twofold B-X insertion, may be crucial for the C-H borylation that leads to the final products. Notably, our results demonstrate the first C-H borylation with a strong B-F bond activated by silylene insertion.