Linked selection and the evolution of altruism in family-structured populations.

Much research on the evolution of altruism via kin selection, group selection, and reciprocity focuses on the role of a single locus or quantitative trait. Very few studies have explored how linked selection, or selection at loci neighboring an altruism locus, impacts the evolution of altruism. While linked selection can decrease the efficacy of selection at neighboring loci, it might have other effects including promoting selection for altruism by increasing relatedness in regions of low recombination. Here, we used population genetic simulations to study how negative selection at linked loci, or background selection, affects the evolution of altruism. When altruism occurs between full siblings, we found that background selection interfered with selection on the altruistic allele, increasing its fixation probability when the altruistic allele was disfavored and reducing its fixation when the allele was favored. In other words, background selection has the same effect on altruistic genes in family-structured populations as it does on other, nonsocial, genes. This contrasts with prior research showing that linked selective sweeps can favor the evolution of cooperation, and we discuss possibilities for resolving these contrasting results.

Acute Myocardial Injury Assessed by High-Sensitivity Cardiac Troponin I Levels in Adult Patients with Early Sepsis at a Tertiary Referral Center in Mexico: An Exploratory Study.

The objective of the study was to describe the frequency of acute myocardial injury (AMI) assessed by high-sensitivity cardiac troponin I (hs-cTnI) levels and to determine the possible initial risk factors (related to the characteristics of the patient, the disease, and the initial management) in a population of adult patients with early sepsis (within the first 72 h of diagnosis) in a single tertiary hospital center in western Mexico. For the inferential statistics, the proportions of the categorical dichotomous variables were compared using the chi-square test. In all analyses, p values less than 0.05 with a 95% confidence interval were considered significant. We included a total of 64 patients diagnosed with early sepsis, of whom 46 presented elevated hs-cTnI and were classified as having AMI. In our study, the frequency of AMI in patients with early sepsis was 71.87%, and no significant differences were found in all of the characteristics of patients with early sepsis with and without AMI, nor was any significant association found with any of the variables analyzed. In the population of western Mexico, the frequency of AMI in patients with early sepsis, assessed by hs-cTnI levels, is high and similar to that reported in other populations worldwide.

AlGaAs Nonlinear Integrated Photonics.

Practical applications implementing integrated photonic circuits can benefit from nonlinear optical functionalities such as wavelength conversion, all-optical signal processing, and frequency-comb generation, among others. Numerous nonlinear waveguide platforms have been explored for these roles; the group of materials capable of combining both passive and active functionalities monolithically on the same chip is III-V semiconductors. AlGaAs is the most studied III-V nonlinear waveguide platform to date; it exhibits both second- and third-order optical nonlinearity and can be used for a wide range of integrated nonlinear photonic devices. In this review, we conduct an extensive overview of various AlGaAs nonlinear waveguide platforms and geometries, their nonlinear optical performances, as well as the measured values and wavelength dependencies of their effective nonlinear coefficients. Furthermore, we highlight the state-of-the-art achievements in the field, among which are efficient tunable wavelength converters, on-chip frequency-comb generation, and ultra-broadband on-chip supercontinuum generation. Moreover, we overview the applications in development where AlGaAs nonlinear functional devices aspire to be the game-changers. Among such applications, there is all-optical signal processing in optical communication networks and integrated quantum photonic circuits.

Relaxed Phase-Matching Constraints in Zero-Index Waveguides.

The utility of all parametric nonlinear optical processes is hampered by phase-matching requirements. Quasi-phase-matching, birefringent phase matching, and higher-order-mode phase matching have all been developed to address this constraint, but the methods demonstrated to date suffer from the inconvenience of only being phase matched for a single, specific arrangement of beams, typically copropagating, resulting in cumbersome experimental configurations and large footprints for integrated devices. Here, we experimentally demonstrate that these phase-matching requirements may be satisfied in a parametric nonlinear optical process for multiple, if not all, configurations of input and output beams when using low-index media. Our measurement constitutes the first experimental observation of direction-independent phase matching for a medium sufficiently long for phase matching to be relevant. We demonstrate four-wave mixing from spectrally distinct co- and counterpropagating pump and probe beams, the backward generation of a nonlinear signal, and excitation by an out-of-plane probe beam. These results explicitly show that the unique properties of low-index media relax traditional phase-matching constraints, which can be exploited to facilitate nonlinear interactions and miniaturize nonlinear devices, thus adding to the established exceptional properties of low-index materials.

Real-World Evidence of Epidemiology and Clinical Outcomes in Multiple Myeloma, Findings from the Registry of Hemato-Oncologic Malignancies in Colombia, Observational Study.

INTRODUCTION/BACKGROUND: Multiple Myeloma (MM) is a plasma cell derived clonal disorder that represents around 1% of all newly diagnosed neoplasms. Limited data regarding MM treatment in Latin America is available, and access to novel agents for a substantial portion of the population is limited by their high costs. MATERIALS (OR PATIENTS) AND METHODS: RENEHOC is a bidirectional (retrospective and prospective) multicenter observational registry of hematological malignancies in Colombia. MM patients included up to July 2020 were analyzed on this report. RESULTS: 890 are reported with a median follow-up of 18 months (IQR: 7-42 months). Patients were classified by age group (≤ or > 65 years). Median age at diagnosis was 67 years (IQR: 59-75 years) and 47.1% of patients were women. 709 patients (79.6%) received Bortezomib-based schemes as part of the first line. Two hundred and fifty-two patients (28.3%) were consolidated with Autologous Stem Cell Transplantation (ASCT) in first-line. ASCT consolidation and age were the main independent factors influencing outcomes; in the non-ASCT cohort, 5-year overall survival was 48.7% (CI 41.8-55.2) compared to 80.7% (CI 73-86.4) in ASCT patients. CONCLUSION: This data depicts the reality of MM in Colombia, which likely reflects other Latin American countries, where access barriers to diagnosis and treatment are echoed in advanced stage diagnosis and a low rate of transplants. These seem to negatively impact survival despite the availability of most novel drugs approved for this disease. Thus, emphasizing the paradox that prevails in most of the region: availability without equitable access.

Multinuclear mesoionic 1,2,3-triazolylidene complexes: design, synthesis, and applications.

The chemistry of multinuclear metal complexes bearing by N-heterocyclic carbene (NHC) ligands, is an area of fast growing interest in modern organometallic chemistry. In particular, complexes supported by mesoionic (MIC) 1,2,3-triazolylidenes are attracting a great deal attention due to their postulated superior donor capacity compared to classical NHC ligands. Despite the readily available synthetic routes to MIC-based ligand platforms featuring several substitution levels, most of the coordination chemistry of triazolylidenes is still dominated by mononuclear complexes. In this short review article, recent progress on the design and synthesis of multinuclear triazolylidene complexes (ranging from di- to tetranuclear species) is discussed. Special emphasis is placed on their structural features, electronic properties and catalytic applications.

Mathematical model reveals that heterogeneity in the number of ion transporters regulates the fraction of mouse sperm capacitation.

Capacitation is a complex maturation process mammalian sperm must undergo in the female genital tract to be able to fertilize an egg. This process involves, amongst others, physiological changes in flagellar beating pattern, membrane potential, intracellular ion concentrations and protein phosphorylation. Typically, in a capacitation medium, only a fraction of sperm achieve this state. The cause for this heterogeneous response is still not well understood and remains an open question. Here, one of our principal results is to develop a discrete regulatory network, with mostly deterministic dynamics in conjunction with some stochastic elements, for the main biochemical and biophysical processes involved in the early events of capacitation. The model criterion for capacitation requires the convergence of specific levels of a select set of nodes. Besides reproducing several experimental results and providing some insight on the network interrelations, the main contribution of the model is the suggestion that the degree of variability in the total amount and individual number of ion transporters among spermatozoa regulates the fraction of capacitated spermatozoa. This conclusion is consistent with recently reported experimental results. Based on this mathematical analysis, experimental clues are proposed for the control of capacitation levels. Furthermore, cooperative and interference traits that become apparent in the modelling among some components also call for future theoretical and experimental studies.

A multi-mechanism approach reduces length of stay in the ICU for severe COVID-19 patients.

PURPOSE: COVID-19 pandemic has multifaceted presentations with rising evidence of immune-mediated mechanisms underplay. We sought to explore the outcomes of severe COVID-19 patients treated with a multi-mechanism approach (MMA) in addition to standard-of-care (SC) versus patients who only received SC treatment. MATERIALS AND METHODS: Data were collected retrospectively for patients admitted to the intensive care unit (ICU). This observational cohort study was performed at five institutions, 3 in the United States and 2 in Honduras. Patients were stratified for MMA vs. SC treatment during ICU stay. MMA treatment consists of widely available medications started immediately upon hospitalization. These interventions target immunomodulation, anticoagulation, viral suppression, and oxygenation. Primary outcomes included in-hospital mortality and length of stay (LOS) for the index hospitalization and were measured using logistic regression. RESULTS: Of 86 patients admitted, 65 (76%) who had severe COVID-19 were included in the study; 30 (46%) patients were in SC group, compared with 35 (54%) patients treated with MMA group. Twelve (40%) patients in the SC group died, compared with 5 (14%) in the MMA group (p-value = 0.01, Chi squared test). After adjustment for gender, age, treatment group, Q-SOFA score, the MMA group had a mean length of stay 8.15 days, when compared with SC group with 13.55 days. ICU length of stay was reduced by a mean of 5.4 days (adjusted for a mean age of 54 years, p-value 0.03) and up to 9 days (unadjusted for mean age), with no significant reduction in overall adjusted mortality rate, where the strongest predictor of mortality was the use of mechanical ventilation. CONCLUSION: The finding that MMA decreases the average ICU length of stay by 5.4 days and up to 9 days in older patients suggests that implementation of this treatment protocol could allow a healthcare system to manage 60% more COVID-19 patients with the same number of ICU beds.

Allelic diversity and patterns of selection at the major histocompatibility complex class I and II loci in a threatened shorebird, the Snowy Plover (Charadrius nivosus).

BACKGROUND: Understanding the structure and variability of adaptive loci such as the major histocompatibility complex (MHC) genes is a primary research goal for evolutionary and conservation genetics. Typically, classical MHC genes show high polymorphism and are under strong balancing selection, as their products trigger the adaptive immune response in vertebrates. Here, we assess the allelic diversity and patterns of selection for MHC class I and class II loci in a threatened shorebird with highly flexible mating and parental care behaviour, the Snowy Plover (Charadrius nivosus) across its broad geographic range. RESULTS: We determined the allelic and nucleotide diversity for MHC class I and class II genes using samples of 250 individuals from eight breeding population of Snowy Plovers. We found 40 alleles at MHC class I and six alleles at MHC class II, with individuals carrying two to seven different alleles (mean 3.70) at MHC class I and up to two alleles (mean 1.45) at MHC class II. Diversity was higher in the peptide-binding region, which suggests balancing selection. The MHC class I locus showed stronger signatures of both positive and negative selection than the MHC class II locus. Most alleles were present in more than one population. If present, private alleles generally occurred at very low frequencies in each population, except for the private alleles of MHC class I in one island population (Puerto Rico, lineage tenuirostris). CONCLUSION: Snowy Plovers exhibited an intermediate level of diversity at the MHC, similar to that reported in other Charadriiformes. The differences found in the patterns of selection between the class I and II loci are consistent with the hypothesis that different mechanisms shape the sequence evolution of MHC class I and class II genes. The rarity of private alleles across populations is consistent with high natal and breeding dispersal and the low genetic structure previously observed at neutral genetic markers in this species.

NHC-Au(i) complexes bearing trispyrazolyl borate (Tp) ligands: efficient platforms for bimetallic species.

Treatment of NHC-AuCl (NHC = IPr and IMes) complexes with equimolar amounts of KTpR2 (R = Me, H) salts in tetrahydrofuran produces in high yields the heteroleptic complexes 3-6 with the general formula NHC-Au-TpR2. As the TpR ligand in complexes 3-6 features a k1-N type coordination toward the gold(i) center, the subsequent addition of group 10 and 11 metal precursors (NiII, PtII, CuII) results in the isolation of heterobimetallic Au/M complexes supported by TpR platforms. All new metal complexes have been fully characterized by elemental analysis and NMR spectroscopy, and in the case of 3, 4 and 6 by X-ray crystallography.

Modular analysis of the control of flagellar Ca2+-spike trains produced by CatSper and CaV channels in sea urchin sperm.

Intracellular calcium ([Ca2+]i) is a basic and ubiquitous cellular signal controlling a wide variety of biological processes. A remarkable example is the steering of sea urchin spermatozoa towards the conspecific egg by a spatially and temporally orchestrated series of [Ca2+]i spikes. Although this process has been an experimental paradigm for reproduction and sperm chemotaxis studies, the composition and regulation of the signalling network underlying the cytosolic calcium fluctuations are hitherto not fully understood. Here, we used a differential equations model of the signalling network to assess which set of channels can explain the characteristic envelope and temporal organisation of the [Ca2+]i-spike trains. The signalling network comprises an initial membrane hyperpolarisation produced by an Upstream module triggered by the egg-released chemoattractant peptide, via receptor activation, cGMP synthesis and decay. Followed by downstream modules leading to intraflagellar pH (pHi), voltage and [Ca2+]i fluctuations. The Upstream module outputs were fitted to kinetic data on cGMP activity and early membrane potential changes measured in bulk cell populations. Two candidate modules featuring voltage-dependent Ca2+-channels link these outputs to the downstream dynamics and can independently explain the typical decaying envelope and the progressive spacing of the spikes. In the first module, [Ca2+]i-spike trains require the concerted action of a classical CaV-like channel and a potassium channel, BK (Slo1), whereas the second module relies on pHi-dependent CatSper dynamics articulated with voltage-dependent neutral sodium-proton exchanger (NHE). We analysed the dynamics of these two modules alone and in mixed scenarios. We show that the [Ca2+]i dynamics observed experimentally after sustained alkalinisation can be reproduced by a model featuring the CatSper and NHE module but not by those including the pH-independent CaV and BK module or proportionate mixed scenarios. We conclude in favour of the module containing CatSper and NHE and highlight experimentally testable predictions that would corroborate this conclusion.

Hydroxyl-functionalized triazolylidene-based PEPPSI complexes: metallacycle formation effect on the Suzuki coupling reaction.

We report the preparation and full characterization of a series of hydroxyl functionalized 1,2,3-triazolylidene-based PEPPSI complexes 2a-c and their catalytic application in the Suzuki cross coupling reaction of aryl chlorides/amides with boronic acids. Under basic reaction conditions, complexes 2a-c show a notable increase in their catalytic efficiency compared with two ether-wingtip functionalized PEPPSI analogues (3 and 4) and a commercially available NHC-Pd complex (5). The catalytic results suggest that deprotonation of the hydroxyl group in complexes 2a-c plays an important role in the overall process. Deprotonation of the alcohol moiety of complexes 2a-b with sodium tert-butoxide allows for the isolation of metallacycles 6a-b, which are proposed as the active species of cross coupling reactions.

Study of the Coordination Modes of Hybrid NNCp Cyclopentadienyl/Scorpionate Ligands in Ir Compounds.

A new coordination mode for the hybrid scorpionate/cyclopentadienyl ligand bpzcp, [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] is observed in iridium complexes. The reaction of the lithium precursor, [Li(bpzcp)(THF)], with a range of [IrCl(diene)]2 compounds leads to an unprecedented binding mode of the hybrid scorpionate/cyclopentadienyl ligand as η5-Cp-coordinated and the formation of Ir(I) derivatives [Ir(η5-Cp-bpzcp)(η4-cod)] (1), [Ir(η5-Cp-bpzcp){η4-CH2═C(Me)C(Me)═CH2}] (2), [Ir(η5-Cp-bpzcp)(η2-coe)2] (3), and [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2] (4). The Ir(I) complex 4 reacts with CO or bromine to afford the compound [Ir(η5-Cp-bpzcp)(CO)2] (5) and the 18e- Ir(III) complex [Ir(κ-N-η5-Cp-bpzcpBr2)Br2] (6), respectively. Reaction of the iridium compounds (2-4) with CuI or [PdCl2(CH3CN)2] yields the heterobimetallic iridium-copper or iridium-palladium complexes [Ir(η5-Cp-bpzcp){η4-CH2═C(Me)C(Me)═CH2}(µ-bpzcp){CuI(κ2-NN-bpzcp)}] (7), [Ir(η5-Cp-bpzcp)(η2-coe)2}(µ-bpzcp){CuI(κ2-NN-bpzcp)}] (8), [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2}(µ-bpzcp){CuI(κ2-NN-bpzcp)}] (9), [Ir(η5-Cp-bpzcp)(coe)2}(µ-bpzcp){PdCl2(κ2-NN-bpzcp)}] (10), and [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2(µ-bpzcp){PdCl2(κ2-NN-bpzcp)}] (11). All products were characterized by spectroscopic methods and the X-ray crystal structures of 1, 2, 3, 4, and 6 were also established.

Expedient Synthesis of Highly Functionalized Abnormal Carbenegold(I) Complexes.

The reaction of 4-substituted imidazol-2-ylidenes with various electrophiles produces a series of 2,4-functionalized imidazolium salts. Subsequent metalation of these precursors using AuCl(SMe2) provides the first examples of highly functionalized abnormal carbenegold(I) complexes. The present protocol introduces a new strategy for the synthesis of metallic abnormal carbenes featuring diverse functional groups.

Network model predicts that CatSper is the main Ca2+ channel in the regulation of sea urchin sperm motility.

Spermatozoa sea urchin swimming behaviour is regulated by small peptides from the egg outer envelope. Speract, such a peptide, after binding to its receptor in Strongylocentrotus purpuratus sperm flagella, triggers a signaling pathway that culminates with a train of intracellular calcium oscillations, correlated with changes in sperm swimming pattern. This pathway has been widely studied but not fully characterized. Recent work on Arbacia punctulata sea urchin spermatozoa has documented the presence of the Ca2+ CatSper channel in their flagella and its involvement in chemotaxis. However, if other calcium channels participate in chemotaxis remains unclear. Here, based on an experimentally-backed logical network model, we conclude that CatSper is fundamental in the S. purpuratus speract-activated sea urchin sperm signaling cascade, although other Ca2+ channels could still be relevant. We also present for the first time experimental corroboration of its active presence in S. purpuratus sperm flagella. We argue, prompted by in silico knock-out calculations, that CatSper is the main generator of calcium oscillations in the signaling pathway and that other calcium channels, if present, have a complementary role. The approach adopted here allows us to unveil processes, which are hard to detect exclusively by experimental procedures.

Descripción de las caracteristicas clínicas de las neoplasias mieloproliferativas crónicas (NMPC). Primer informe del registro colombiano de NMPC / Description of the clinical characteristics of chronic myeloproliferative neoplasms (MPNs). First report of the colombian registry of MPNs

Resumen Introducción y objetivos: las neoplasias mieloproliferativas crónicas (NMPC) son relativamente raras, con incidencias que varían entre 0.47-1.03/100 000 habitantes. Se presenta el primer informe del trabajo del registro colombiano de NMPC, cuyo objetivo es describir las características clínicas de estos pacientes en nuestro país. Material y métodos: estudio descriptivo observacional, multicéntrico, retrospectivo y prospectivo en ocho centros del país, de abril de 2013 a diciembre de 2014. Las variables cualitativas se presentan con frecuencias absolutas y relativas; y las cuantitativas se resumen en medidas de tendencia central y dispersión. Resultados: once centros fueron aprobados, ocho ingresaron pacientes. En los primeros 179 casos reportados, 50% eran hombres, la edad promedio al diagnóstico 58.7 años (rango 19-92). Noventa y tres muestran trombocitemia esencial (TE); 55, policitemia vera (PV); y 31, mielofibrosis (MF). El 41% tenía esplenomegalia al diagnóstico; el 20% tuvo complicaciones trombóticas; y 12.85%, sangrado. Sólo en 57.5% se realizó JAK; de ellos, en 53.5% fue positivo, en especial sólo 60% de las PV. El 8% de los casos no tenía estudio de médula ósea, el 29.3% tiene algún grado de fibrosis. El hallazgo más frecuente fue hiperplasia megacariocítica en 59.78%. Más de 50% de pacientes estaban sintomáticos al diagnóstico. Sólo el 11% no recibió tratamiento farmacológico; los más frecuentes fueron hidroxiurea en 149 casos y ASA en 79. Con promedio de seguimiento de 52.6 meses; el 97.21% de los pacientes están vivos. Conclusiones: los hallazgos sugieren que algunas características de las NMPC podrían ser diferentes a lo reportado en otras series, lo que valida la importancia del esfuerzo de recoger información local.

Abstract Introduction and objectives: chronic MPNs are relatively rare, with incidences varying between 0.47-1.03 / 100 000 inhabitants. The first report of the work of the Colombian registry of chronic MPNs, whose objective is to describe the clinical characteristics of these patients in our country, is presented. Materials and methods: descriptive observational, multicenter, retrospective and prospective study in eight centers of the country, from April 2013 to December 2014. Qualitative variables are presented with absolute and relative frequencies, and the quantitative ones are summarized in measures of central tendency and dispersion. Results: eleven centers were approved; 8 admitted patients. In the first 179 cases reported, 50% were men; the average age at diagnosis was 58.7 years (range 19-92). Ninety-three present essential thrombocythemia (ET); 55, polycythemia vera (PV); and 31, myelofibrosis (MF). 41% had splenomegaly at diagnosis; 20% had thrombotic complications, and 12.85%, bleeding. JAK was performed in only 57.5%. Of them, in 53.5% was positive, especially in only 60% of the PV. 8% of the cases had no bone marrow study; 29.3% had some degree of fibrosis. The most frequent finding was megakaryocytic hyperplasia in 59.78%. More than 50% of patients were symptomatic at diagnosis. Only 11% did not receive pharmacological treatment, being the most frequent hydroxyurea in 149 cases and ASA in 79, with an average follow-up of 52.6 months. 97.21% of patients are alive. Conclusions: the findings suggest that some characteristics of chronic MPNs could be different from those reported in other series, which validates the importance of the effort to collect local information.

Bridged N-Heterocyclic/Mesoionic (NHC/MIC) Heterodicarbenes as Ligands for Transition Metal Complexes.

Following a copper catalyzed alkyne azide cycloaddition (CuAAC) and N-alkylation protocols, we report the preparation of a hybrid N-heterocyclic/mesoionic [NHC(H+)-MIC(H+)][2I]2- salt (1) in high yields. The treatment of salt 1 with Cu2O and KI yields a second hybrid NHC/MIC proligand featuring a tetraiodocuprate anion [NHC(H+)-MIC(H+)][Cu2I4]2- (2). Through selective deprotonation and metalation, both salts 1 and 2 can generate either the chelate heterodicarbene complexes (3) with the rare [NHC·(M)·MIC]+[MX2]- general formula (M = PdII, RhI) or NHC-anchored/pendent triazolium species (4) [NHC·(M)-MIC(H+)]. If the triazolium moiety of type 4 complexes is deprotonated with KHMDS in the presence of a second metal center, a series of heterobimetallic complexes of the type [NHC·(M)-MIC·(M')] (5) are achieved. Interestingly, the reaction of salt 2 with KHMDS yields the bimetallic copper heterodicarbene (6) which can be a useful transfer reagent for the preparation of type 3 complexes. A variety of synthetic routes for the preparation of complexes 3-5 and their full characterization in solution and in the solid state will be discussed.

Visible-Light-Promoted AuI to AuIII Oxidation in Triazol-5-ylidene Complexes.

Reaction of triazolium precursors [MIC(CH2 )n - H+ ]I- (n=1-3) with potassium hexamethyldisilazane (KHMDS) and AuCl(SMe2 ) generates the gold(I) complexes of the type MIC(CH2 )n ⋅AuI. Visible light exposure of the latter complexes promotes a spontaneous disproportionation process rendering gold(III) complexes of the type [{MIC(CH2 )n }2 ⋅AuI2 ]+ I- . Both the AuI and AuIII complex series were tested in the catalytic hydrohydrazination of terminal alkynes using hydrazine as nitrogen source.

Activation of aldehydes by exocyclic iridium(i)-η4:π2-diene complexes derived from 1,3-oxazolidin-2-ones.

The Ir(i) complexes [TpMe2Ir(η4-1,4-diene)] 2b and 2c react thermally with a variety of aromatic aldehydes, 3a-e, to generate the metallabicyclic compounds 4e-k and the Fischer-type carbenes 5a-b in moderate yields. These reactions are proposed to take place with the initial formation of η1-aldehyde adducts as key intermediates. The formation of the metallabicyclic compounds 4e-k involves a formal decarboxylation process at the exo-2-oxazolidinone diene and an ortho metallation of the aromatic ring. The generation of the Fischer-type carbenes 5a-b is the result of a series of metal-based rearranged intermediates with no decarboxylation observed. Treatment of the η4-diene complex 2b with a variety of Lewis bases induces a change in the binding mode of the diene ligand from η4:π2 to η2:σ2 to form the Ir(iii) derivatives 6b-d of composition TpMe2Ir-(η4:π2-1,4-diene)(L) (L = CO, MeCN, and C5H5N). A study of reactions of complex 2b with either mono- or poly-deuterated aldehydes was performed to understand the mechanisms of such processes. The results of these studies were used to determine plausible formation mechanisms of the metallabicyclic compounds 4e-4k and Fischer-type carbenes 5a-b compound series. These mechanisms were corroborated by density functional theory (DFT) calculations of the free energy profiles.