Correction: An un-forgotten classic: the nitro-Mannich reaction between nitrones and silyl nitronates catalysed by B(C6F5)3.

[This corrects the article DOI: 10.1039/D3SC05672D.].

Synthetic and Mechanistic Studies into the Reductive Functionalization of Nitro Compounds Catalyzed by an Iron(salen) Complex.

We report on the use of a simple, bench-stable [Fe(salen)2]-µ-oxo precatalyst in the reduction of nitro compounds. The reaction proceeds at room temperature across a range of substrates, including nitro aromatics and aliphatics. By changing the reducing agent from pinacol borane (HBpin) to phenyl silane (H3SiPh), we can chemoselectively reduce nitro compounds while retaining carbonyl functionality. Our mechanistic studies, which include kinetics, electron paramagnetic resonance (EPR), mass spectrometry, and quantum chemistry, indicate the presence of a nitroso intermediate and the generation of an on-cycle iron hydride as a key catalytic intermediate. Based on this mechanistic insight, we were able to extend the chemistry to hydroamination and identified a simple substrate feature (alkene lowest unoccupied molecular orbital (LUMO) energy) that could be used to predict which alkenes would result in productive catalysis.

Tuning Excited State Character in Iridium(III) Photosensitizers and Its Influence on TTA-UC.

A series of mixed ligand, photoluminescent organometallic Ir(III) complexes have been synthesized to incorporate substituted 2-phenyl-1H-naphtho[2,3-d]imidazole cyclometalating ligands. The structures of three example complexes were categorically confirmed using X-ray crystallography each sharing very similar structural traits including evidence of interligand hydrogen bond contacts that account for the shielding effects observed in the 1H NMR spectra. The structural iterations of the cyclometalated ligand provide tuning of the principal electronic transitions that determine the visible absorption and emission properties of the complexes: emission can be tuned in the visible region between 550 and 610 nm and with triplet lifetimes up to 10 µs. The nature of the emitting state varies across the series of complexes, with different admixtures of ligand-centered and metal-to-ligand charge transfer triplet levels evident. Finally, the use of the complexes as photosensitizers in triplet-triplet annihilation energy upconversion (TTA-UC) was investigated in the solution state. The study showed that the complexes possessing the longest triplet lifetimes showed good viability as photosensitizers in TTA-UC. Therefore, the use of an electron-withdrawing group on the 2-phenyl-1H-naphtho[2,3-d]imidazole ligand framework can be used to rationally promote TTA-UC using this class of complex.

Diverse Reactivity of Amidinate-Supported Boron Centers with the Hypersilyl Anion and Access to a Monomeric Secondary Boron Hydride.

Diverse reactivity of the bulky tris(trimethylsilyl)silyl substituent [Si(SiMe3)3], also known as the hypersilyl group, was observed for amidinate-supported dichloro- and phenylchloroborane complexes. Treatment of the dichloroborane with potassium tris(trimethylsilyl)silyl led to the activation of the backbone ß-carbon center and formation of saturated four-membered heterocyclic chloroboranes R'{Si(SiMe3)3}C(NR)2BCl [R' = Ph, R = Cy (3); R' = Ph, R = iPr (6); R' = tBu, R = Cy (8)], whereas the four-membered amidinate hypersilyl-substituted phenyl borane 4 {PhC(NCy)2B(Ph)[Si(SiMe3)3]} was observed for the case of an amidinate-supported phenylchloroborane. The highly deshielded 11B NMR spectroscopic resonance and the distinct difference in the 29Si NMR spectrum confirmed the presence of a σ-donating hypersilyl effect on compounds 3, 6, and 8. Reaction of 3 with the Lewis acid AlCl3 led to the formation of complex 11 in which an unusual cleavage of one of the C-N bonds of the amidinate backbone is observed. Nucleophilic substitution at the boron center of saturated chloroborane 3 with phenyllithium generated the phenylborane derivative 12, whereas the secondary monomeric boron hydride 13 was observed after treatment with alane (AlH3). All compounds (2-13) have been fully characterized by NMR spectroscopy and single-crystal X-ray structure determination studies.

[{SiNDipp}MgNa]2: A Potent Molecular Reducing Agent.

The bimetallic species, [{SiNDipp}MgNa]2 [{SiNDipp} = {CH2SiMe2N(Dipp)}2; (Dipp = 2,6-i-Pr2C6H3)], is shown to be a potent reducing agent, able to effect one- or two-electron reduction of either dioxygen, TEMPO, anthracene, benzophenone, or diphenylacetylene. In most cases, the bimetallic reaction products imply that the dissimilar alkaline metal centers react with a level of cooperativity. EPR analysis of the benzophenone-derived reaction and the concurrent isolation of [{SiNDipp}Mg(OCPh2)2], however, illustrate that treatment with such reducible, but O-basic, species can also result in reactivity in which the metals provide independent reaction products. The notable E-stereochemistry of the diphenylacetylene reduction product prompted a computational investigation of the PhC≡CPh addition. This analysis invokes a series of elementary steps that necessitate ring-opening via Mg+ → Na+ amido group migration of the SiNDipp ligand, providing insight into the previously observed lability of the bidentate dianion and its consequent proclivity toward macrocyclization.

An un-forgotten classic: the nitro-Mannich reaction between nitrones and silyl nitronates catalysed by B(C6F5)3.

Herein we report the B(C6F5)3-catalysed nitro-Mannich reaction between nitrones and silyl nitronates, affording silyl-protected α-nitro hydroxylamines with yields up to 99% and diastereoselectivities up to 99 : 1. Crucially, the obtained products can be converted into 1,2-diamines under simple reductive conditions. This work provides a new orthogonal method to the existing routes for the instalment of a nitro moiety under Lewis acid catalysed conditions, and expands the state-of-the-art substrate scope with respect to the silyl nitronates.

Trainee-perceived benefits of a virtual temporal bone competition.

OBJECTIVE: To assess the perceived benefits of a novel educational approach for otolaryngology trainees: a virtual reality temporal bone simulator drilling competition. METHODS: Regional otolaryngology trainees participated in the competition. Drilling activities using the Voxel-Man TempoSurg simulator were scored by experts. Questionnaires that contained questions covering motivators for attending, perceived learning and enjoyment were sent to participants. Agreement with statements was measured on a 10-point Likert scale (1 = strongly disagree, 10 = strongly agree). RESULTS: Eighteen trainees participated. The most cited reason for attending was for learning and/or education (61 per cent), with most attendees (72 per cent) believing that competition encourages more reading and/or practice. Seventeen attendees (94 per cent) believed Voxel-Man TempoSurg-based simulation would help to improve intra-operative performance in mastoidectomy (mean 7.83 ± 1.47, p < 0.001) and understanding of anatomy (mean 8.72 ± 1.13, p < 0.001). All participants rated the competition as 'fun' and 83 per cent believed the competitive element added to this. CONCLUSION: The virtual reality temporal bone competition is a novel educational approach within otolaryngology that was positively received by otolaryngology trainees.

Recent Advances in Asymmetric Catalysis Using p-Block Elements.

The development of new methods for enantioselective reactions that generate stereogenic centres within molecules are a cornerstone of organic synthesis. Typically, metal catalysts bearing chiral ligands as well as chiral organocatalysts have been employed for the enantioselective synthesis of organic compounds. In this review, we highlight the recent advances in main group catalysis for enantioselective reactions using the p-block elements (boron, aluminium, phosphorus, bismuth) as a complementary and sustainable approach to generate chiral molecules. Several of these catalysts benefit in terms of high abundance, low toxicity, high selectivity, and excellent reactivity. This minireview summarises the utilisation of chiral p-block element catalysts for asymmetric reactions to generate value-added compounds.

[Mindfulness meditation and art therapy for Alzheimer's patients and their caregivers]. / La méditation et l'art-thérapie au service des patients souffrant de la maladie d'Alzheimer.

Alzheimer's disease affects nearly three million people in France, and requires training for both healthcare professionals and caregivers. Our study underlines the value of supporting an adapted program based on mindfulness meditation, to reduce anxiety and stress for patients and their caregivers.

Insights into Single-Electron-Transfer Processes in Frustrated Lewis Pair Chemistry and Related Donor-Acceptor Systems in Main Group Chemistry.

The activation and utilization of substrates mediated by Frustrated Lewis Pairs (FLPs) was initially believed to occur solely via a two-electron, cooperative mechanism. More recently, the occurrence of a single-electron transfer (SET) from the Lewis base to the Lewis acid was observed, indicating that mechanisms that proceed via one-electron-transfer processes are also feasible. As such, SET in FLP systems leads to the formation of radical ion pairs, which have recently been more frequently observed. In this review, we aim to discuss the seminal findings regarding the recently established insights into the SET processes in FLP chemistry as well as highlight examples of this radical formation process. In addition, applications of reported main group radicals will also be reviewed and discussed in the context of the understanding of SET processes in FLP systems.

B(3,4,5-F3H2C6)3 Lewis acid-catalysed C3-allylation of indoles.

Herein we report the B(3,4,5-F3H2C6)3-catalysed C3-allylation of indoles using allylic esters. 25 examples of C3-allylated products are presented in up to 97% yield. The mechanism for the reaction was explored using detailed Density Functional Theory (DFT) studies.

Heterogeneous Photocatalytic Recycling of FeX2 /FeX3 for Efficient Halogenation of C-H Bonds Using NaX.

Environmental-friendly halogenation of C-H bonds using abundant, non-toxic halogen salts is in high demand in various chemical industries, yet the efficiency and selectivity of laboratory available protocols are far behind the conventional photolytic halogenation process which uses hazardous halogen sources. Here we report an FeX2 (X=Br, Cl) coupled semiconductor system for efficient, selective, and continuous photocatalytic halogenation using NaX as halogen source under mild conditions. Herein, FeX2 catalyzes the reduction of molecular oxygen and the consumption of generated oxygen radicals, thus boosting the generation of halogen radicals and elemental halogen for direct halogenation and indirect halogenation via the formation of FeX3 . Recycling of FeX2 and FeX3 during the photocatalytic process enables the halogenation of a wide range of hydrocarbons in a continuous flow, rendering it a promising method for applications.

Copper Cocatalyst Modulated Radical Generation for Selective Heterogeneous Photosynthesis of α-Haloketones.

The α-haloketones are important precursors for synthetic chemistry and pharmaceutical applications; however, their production relies heavily on traditional synthetic methods via halogenation of ketones that are toxic and environmentally risky. Here, we report a heterogeneous photosynthetic strategy of α-haloketone production from aromatic olefins using copper-modified graphitic carbon nitride (Cu-C3N4) under mild reaction conditions. By employing NiX2 (X = Cl, Br) as the halogen source, a series of α-haloketones can be synthesized using atmospheric air as the oxidant under visible-light irradiation. In comparison with pristine carbon nitride, the addition of Cu as a cocatalyst provides a moderate generation rate of halogen radicals and selective reduction of molecular oxygen into •OOH radicals, thus leading to a high selectivity to α-haloketones. The Cu-C3N4 also exhibits high stability and versatility, rendering it a promising candidate for solar-driven synthetic applications.

B(C6F5)3-Catalyzed Diastereoselective and Divergent Reactions of Vinyldiazo Esters with Nitrones: Synthesis of Highly Functionalized Diazo Compounds.

Herein we report a mild, transition-metal-free, highly diastereoselective Lewis acid catalyzed methodology toward the synthesis of isoxazolidine-based diazo compounds from the reaction between vinyldiazo esters and nitrones. Interestingly, the isoxazolidine products were identified to have contrasting diastereoselectivity to previously reported metal-catalyzed reactions. Furthermore, the same catalyst can be used with enol diazo esters, prompting the formation of Mukaiyama-Mannich products. These diazo products can then be further functionalized to afford benzo[b]azepine and pyrrolidinone derivatives.

Reduction of Na+ within a {Mg2 Na2 } Assembly.

Ionic compounds containing sodium cations are notable for their stability and resistance to redox reactivity unless highly reducing electrical potentials are applied. Here we report that treatment of a low oxidation state {Mg2 Na2 } species with non-reducible organic bases induces the spontaneous and completely selective extrusion of sodium metal and oxidation of the MgI centers to the more conventional MgII state. Although these processes are also characterized by a structural reorganisation of the initially chelated diamide spectator ligand, computational quantum chemical studies indicate that intramolecular electron transfer is abetted by the frontier molecular orbitals (HOMO/LUMO) of the {Mg2 Na2 } ensemble, which arise exclusively from the 3s valence atomic orbitals of the constituent sodium and magnesium atoms.

Lewis Acid Assisted Brønsted Acid Catalysed Decarbonylation of Isocyanates: A Combined DFT and Experimental Study.

An efficient and mild reaction protocol for the decarbonylation of isocyanates has been developed using catalytic amounts of Lewis acidic boranes. The electronic nature (electron withdrawing, electron neutral, and electron donating) and the position of the substituents (ortho/meta/para) bound to isocyanate controls the chain length and composition of the products formed in the reaction. Detailed DFT studies were undertaken to account for the formation of the mono/di-carboxamidation products and benzoxazolone compounds.

The 'muscle wonton' repair - A case series of internal carotid artery injuries at a single Centre during its 10-year experience in endoscopic transsphenoidal pituitary surgery.

INTRODUCTION: Although rare, injury to the internal carotid artery (ICA) during pituitary surgery may result in serious morbidity such as stroke or death. This case series explores a single centre's incidence and outcomes of ICA injury during endoscopic transsphenoidal pituitary surgery, discusses the current management options, and introduces the 'muscle wonton' (morcellised muscle wrapped in a single sheet of Surgicel®) as being a viable repair option. METHODS: All patients undergoing pituitary operations from January 2010 to December 2019 at the Queen Elizabeth Hospital, Birmingham, UK were included. Primary outcome was number of internal carotid artery injuries during pituitary surgery. Secondary outcome measures included pre-operative (demographic, risk factors such as previous radiotherapy, number of previous operations, imaging available), operative (intra-operative image guidance, intra-operative doppler ultrasound, which side ICA was damaged, repair technique) and post-operative result (death, cranial nerve VI palsy, or stroke). RESULTS: 7 out of 893 patients (0.8%) were identified as having an ICA injury. Four of the injuries were left sided. Average age was 54 years old, five were male. In four of the ICA injuries intra-operative navigation imaging was used, and a further two concurrently used ultrasound doppler. Three of the seven cases resulted in permanent morbidity (stroke). There were no other consistent demographic, pre-operative, operative, or post-operative similarities. The two patients with muscle wonton repair suffered no permanent serious complication of ICA injury (i.e. death, abducens nerve palsy, stroke). DISCUSSION: Our findings resemble the current literature, with left sided ICA injury being more common. Different methods for repairing ICA injury exist, however morcellised muscle patches have shown significant promise in animal models, and the perforated Surgicel® helps create an easy delivery method. The muscle wonton is a viable surgical option for repairing ICA injuries during pituitary surgery.

Perioperative management of lithium in the patient undergoing pituitary surgery: a case report.

Lithium is a psychotropic drug used primarily in the treatment of bipolar disorder. It is renally excreted and characteristically causes nephrogenic diabetes insipidus as an adverse drug reaction. Lithium also requires serum level monitoring as there is a narrow therapeutic window and untreated toxicity can result in neurological sequelae including drowsiness, coma, seizures, and ultimately death. We present the case of a 65-year old man admitted for pituitary surgery complicated by post-operative difficult fluid management and subsequent lithium toxicity. We highlight this rare situation and the need to be vigilant in the peri-operative period with any patients on lithium who undergo pituitary surgery.

Long-lived, near-IR emission from Cr(III) under ambient conditions.

Bis-terdentate (N^N^N) ligands coordinated to Cr(III) yield complexes that display near-IR emission under aerated solvent conditions at room temperature.