Effect of surgical experience and spine subspecialty on the reliability of the {AO} Spine Upper Cervical Injury Classification System

OBJECTIVE The objective of this paper was to determine the interobserver reliability and intraobserver reproducibility of the AO Spine Upper Cervical Injury Classification System based on surgeon experience (< 5 years, 5–10 years, 10–20 years, and > 20 years) and surgical subspecialty (orthopedic spine surgery, neurosurgery, and "other" surgery). METHODS A total of 11,601 assessments of upper cervical spine injuries were evaluated based on the AO Spine Upper Cervical Injury Classification System. Reliability and reproducibility scores were obtained twice, with a 3-week time interval. Descriptive statistics were utilized to examine the percentage of accurately classified injuries, and Pearson’s chi-square or Fisher’s exact test was used to screen for potentially relevant differences between study participants. Kappa coefficients (κ) determined the interobserver reliability and intraobserver reproducibility. RESULTS The intraobserver reproducibility was substantial for surgeon experience level (< 5 years: 0.74 vs 5–10 years: 0.69 vs 10–20 years: 0.69 vs > 20 years: 0.70) and surgical subspecialty (orthopedic spine: 0.71 vs neurosurgery: 0.69 vs other: 0.68). Furthermore, the interobserver reliability was substantial for all surgical experience groups on assessment 1 (< 5 years: 0.67 vs 5–10 years: 0.62 vs 10–20 years: 0.61 vs > 20 years: 0.62), and only surgeons with > 20 years of experience did not have substantial reliability on assessment 2 (< 5 years: 0.62 vs 5–10 years: 0.61 vs 10–20 years: 0.61 vs > 20 years: 0.59). Orthopedic spine surgeons and neurosurgeons had substantial intraobserver reproducibility on both assessment 1 (0.64 vs 0.63) and assessment 2 (0.62 vs 0.63), while other surgeons had moderate reliability on assessment 1 (0.43) and fair reliability on assessment 2 (0.36). CONCLUSIONS The international reliability and reproducibility scores for the AO Spine Upper Cervical Injury Classification System demonstrated substantial intraobserver reproducibility and interobserver reliability regardless of surgical experience and spine subspecialty. These results support the global application of this classification system

Wingtip substituents tailor the catalytic activity of ruthenium triazolylidene complexes in base-free alcohol oxidation

A series of RuII (η6-arene) complexes with 1,2,3-triazolylidene ligands comprising different aryl and alkyl wingtip groups have been prepared and characterized by NMR spectroscopy, microanalysis, and in one case by X-ray diffraction. All complexes are active catalyst precursors for the oxidation of alcohols to the corresponding aldehydes/ketones without the need of an oxidant or base as additive. The wingtip groups have a direct impact on the catalytic activity, alkyl wingtips providing the most active species while aryl wingtip groups induce lower activity. An N-bound phenyl group was the most inhibiting wingtip group due to cyclometalation. Arene dissociation was observed as a potential catalyst deactivation pathway.European Research CouncilScience Foundation Irelan

Carbene transfer from triazolylidene gold complexes as a potent strategy for inducing high catalytic activity

A series of gold(I) complexes [AuCl(trz)] were synthesized that contain 1,2,3-triazolylidene (trz) ligands with variable wingtip groups. In the presence of AgBF4, these complexes undergo ligand redistribution to yield cationic complexes [Au(trz)2]BF4 in high yields as a result of efficient carbene transfer. Identical reactivity patterns were detected for carbene gold complexes comprised of Arduengo-type IMes ligands (IMes=N,N⠲-dimesityl-imidazol-2-ylidene). Reaction of cationic complexes [Au(trz)2]+ with [AuCl(trz⠲)] afforded the heteroleptic complex [Au(trz)(trz⠲)]+ and [AuCl(trz)] (trz, trz⠲=triazolylidene ligands with different wingtip groups). Carbene transfer occurs spontaneously, yet is markeldy rate-enhanced in the presence of Ag+. The facile carbene transfer was exploited as a catalyst activation process to form active gold species for the aldol condensation of isocyanides and aldehydes to form oxazolines. The catalytic activity is strongly dependent on the presence of Ag+ ions to initiate catalyst activation. High turnovers (105) and turnover frequencies (10 4 h-1) were accomplished. Structural analysis at early stages of the reaction support the critical role of triazolylidene dissociation to activate the precatalyst and dynamic light scattering revealed the presence of nanoparticles (±100 nm diameter) as potential catalytically active species. Furthermore, the triazolylidene scaffold had no impact on the diastereoselectivity of the oxazoline formation, and chiral triazolylidenes did not induce any asymmetry in the product. The facile dissociation of carbenes from [AuCl(carbene)] in the presence of Ag+ ions suggests a less stable Au-Ccarbene interaction than often assumed, with potential implications for gold-catalyzed reactions that employ a silver salt as (putative) halide scavenger.European Research CouncilScience Foundation IrelandJSPS Funding Program for Next Generation World-Leading Researcher

Synthesis and tunability of abnormal 1,2,3-triazolylidene palladium and rhodium complexes

Palladation of N3-alkylated 1,2,3-triazolium salts with Pd(OAc)₂ afforded a μ²−I₂ bridged bimetallic complex [Pd(trz)I₂]₂ and monometallic bis(carbene) complexes Pd(trz)₂I₂ as a mixture of trans and cis isomers (trz = 1,2,3-triazol-5- ylidene). Addition of excess halide or modification of the palladation procedure from direct functionalization to a transmetalation sequence involving a silver intermediate allowed for chemoselective formation of the bis(carbene) complex, while subsequent anion metathesis with NaI produced the monometallic bis(carbene) complexes exclusively. Modification of the wingtip group had little influence on the metalation to palladium or rhodium(I) via transmetalation. According to NMR analysis using δC and ¹JRh−C, subtle but noticeable tunability of the metal electronic properties was identified. In addition, phenyl wingtip groups as N- substituents in the triazolylidene ligands were susceptible to cyclopalladation in the presence of NaOAc and are thus not chemically inert

Synthesis and catalytic alcohol oxidation and ketone transfer hydrogenation activity of donor-functionalized mesoionic triazolylidene ruthenium(II) complexes

We report on the synthesis of a variety of C,E-bidentate triazolylidene ruthenium complexes that comprise different donor substituents E (E=C: phenyl anion; E=O: carboxylate, alkoxide; E=N: pyridine at heterocyclic carbon or nitrogen). Introduction of these donor functionalities is greatly facilitated by the synthetic versatility of triazoles, and their facile preparation routes. Five different complexes featuring a C,E-coordinated ruthenium center with chloride/cymene spectator ligands and three analogous solvento complexes with MeCN spectator ligands were prepared and evaluated as catalyst precursors for direct base- and oxidant-free alcohol dehydrogenation, and for transfer hydrogenation using basic iPrOH as a source of dihydrogen. In both catalytic reactions, the neutral/mono-cationic complexes with chloride/cymene spectator ligands performed better than the solvento ruthenium complexes. The donor functionality had a further profound impact on catalytic activity. For alcohol dehydrogenation, the C,C-bidentate phenyl-triazolylidene ligand induced highest conversions, while carboxylate or pyridine donor sites gave only moderate activity or none at all. In contrast, transfer hydrogenation is most efficient when a pyridyl donor group is linked to the triazolylidene via the heterocyclic carbon atom, providing turnover frequencies as high as 1400 h-1 for cyclohexanone transfer hydrogenation. The role of the donor group is discussed in mechanistic terms.European Research CouncilScience Foundation Irelan

Synthesis and Tunability of Abnormal 1,2,3-Triazolylidene Palladium and Rhodium Complexes

Palladation of N3-alkylated 1,2,3-triazolium salts with Pd(OAc)2 afforded a μ2−I2 bridged bimetallic complex [Pd(trz)I2]2 and monometallic bis(carbene) complexes Pd(trz)2I2 as a mixture of trans and cis isomers (trz = 1,2,3-triazol-5-ylidene). Addition of excess halide or modification of the palladation procedure from direct functionalization to a transmetalation sequence involving a silver intermediate allowed for chemoselective formation of the bis(carbene) complex, while subsequent anion metathesis with NaI produced the monometallic bis(carbene) complexes exclusively. Modification of the wingtip group had little influence on the metalation to palladium or rhodium(I) via transmetalation. According to NMR analysis using δC and 1JRh−C, subtle but noticeable tunability of the metal electronic properties was identified. In addition, phenyl wingtip groups as N-substituents in the triazolylidene ligands were susceptible to cyclopalladation in the presence of NaOAc and are thus not chemically inert.University College DublinSwiss National Science FoundationMarie-Curie IEFAlfred Werner Foundatio

PEPPSI-Type Palladium Complexes Containing Basic 1,2,3-Triazolylidene Ligands and Their Role in Suzuki-Miyaura Catalysis

A series of PEPPSI-type palladium(II) complexes was synthesized that contain 3-chloropyridine as an easily removable ligand and a triazolylidene as a strongly donating mesoionic spectator ligand. Catalytic tests in Suzuki–Miyaura cross-coupling reactions revealed the activity of these complexes towards aryl bromides and aryl chlorides at moderate temperatures (50 °C). However, the impact of steric shielding was the inverse of that observed with related normal Nheterocyclic carbenes (imidazol-2-ylidenes) and sterically congested mesityl substituents induced lower activity than small alkyl groups. Mechanistic investigations, including mercury poisoning experiments, TEM analyses, and ESI mass spectrometry, provide evidence for ligand dissociation and the formation of nanoparticles as a catalyst resting state. These heterogeneous particles provide a reservoir for soluble palladium atoms or clusters as operationally homogeneous catalysts for the arylation of aryl halides. Clearly, the substitution of a normal N-heterocyclic carbene for a more basic triazolylidene ligand in the precatalyst has a profound impact on the mode of action of the catalytic system.European Research CouncilScience Foundation Irelan

Carbene Transfer from Triazolylidene Gold Complexes as a Potent Strategy for Inducing High Catalytic Activity

A series of gold­(I) complexes [AuCl­(trz)] were synthesized that contain 1,2,3-triazolylidene (trz) ligands with variable wingtip groups. In the presence of AgBF₄, these complexes undergo ligand redistribution to yield cationic complexes [Au­(trz)₂]­BF₄ in high yields as a result of efficient carbene transfer. Identical reactivity patterns were detected for carbene gold complexes comprised of Arduengo-type IMes ligands (IMes = <i>N</i>,<i>N</i>′-dimesityl-imidazol-2-ylidene). Reaction of cationic complexes [Au­(trz)₂]⁺ with [AuCl­(trz′)] afforded the heteroleptic complex [Au­(trz)­(trz′)]⁺ and [AuCl­(trz)] (trz, trz′ = triazolylidene ligands with different wingtip groups). Carbene transfer occurs spontaneously, yet is markeldy rate-enhanced in the presence of Ag⁺. The facile carbene transfer was exploited as a catalyst activation process to form active gold species for the aldol condensation of isocyanides and aldehydes to form oxazolines. The catalytic activity is strongly dependent on the presence of Ag⁺ ions to initiate catalyst activation. High turnovers (10⁵) and turnover frequencies (10⁴ h^–1) were accomplished. Structural analysis at early stages of the reaction support the critical role of triazolylidene dissociation to activate the precatalyst and dynamic light scattering revealed the presence of nanoparticles (±100 nm diameter) as potential catalytically active species. Furthermore, the triazolylidene scaffold had no impact on the diastereoselectivity of the oxazoline formation, and chiral triazolylidenes did not induce any asymmetry in the product. The facile dissociation of carbenes from [AuCl­(carbene)] in the presence of Ag⁺ ions suggests a less stable Au–C_carbene interaction than often assumed, with potential implications for gold-catalyzed reactions that employ a silver salt as (putative) halide scavenger

Arylative Desulfonation of Diarylmethyl Phenyl Sulfone with Arenes Catalyzed by Scandium Triflate

A scandium-triflate-catalyzed arylative desulfonation of diarylmethyl phenyl sulfones with arenes and heteroarenes was established. A variety of both sulfone and arene substrates were reacted to afford symmetric and nonsymmetric triarylmethanes in good yields. Further transformations of the resulting triarylmethanes and application to the concise synthesis of a bactericidal agent analogue were also demonstrated