Trapping Elusive Cp*Co(III) Metallacycles: Implications in C-H Functionalization Processes

La conversió d'enllaços carboni–hidrogen en enllaços carboni–carboni o carboni–heteroàtom és una de les reaccions més atractives dins de la química orgànica. Entre les diferents estratègies desenvolupades al llarg de les últimes dècades, l'activació selectiva d'enllaços C–H, promoguda per metalls de transició, amb l'ajuda d'un grup director, s'ha convertit en una alternativa molt atractiva a les tradicionals reaccions d'acoblament creuat. El desenvolupament d'aquest camp ha estat dominat per l'ús de catalitzadors de metalls nobles. No obstant això, en els últims anys, catalitzadors de metalls més barats i abundants, com el cobalt, han esdevingut una alternativa molt interessant. En aquest context, l'ús de complexos de Cp*CoIII ha rebut especial atenció a causa de la seva capacitat per a promoure una gran varietat de reaccions de formació d'enllaços C–C i C–X. Malgrat els avanços realitzats, aquests sistemes encara estan en la seva infància en comparació amb els catalitzadors de Rh i Pd, a causa de la falta de coneixement fonamental. L'estudi sobre la naturalesa de les espècies reactives o el mecanisme implicat en aquestes transformacions s'ha vist obstaculitzat per la dificultat de detectar intermedis de reacció. Intrigats per aquesta problemàtica, en aquesta tesi doctoral hem explorat: i) el desenvolupament de noves estratègies per a accedir a aquests intermedis de reacció; ii) l'ús d'aquests metal·lacicles de Cp*CoIII, no sols per a obtenir informació del mecanisme sobre diferents reaccions catalitzades per aquests compostos, sinó també per a millorar la seva eficiència; i finalment, iii) l'estudi de l'efecte d'alguns additius en les etapes elementals involucrades en els cicles catalítics. El coneixement fonamental generat durant aquesta tesi doctoralLa conversión de enlaces carbono–hidrógeno en enlaces carbono–carbono o carbono–heteroátomo es una de las reacciones más atractivas dentro de la química orgánica. Entre las diferentes estrategias desarrolladas a lo largo de las últimas décadas, la activación selectiva de enlaces C–H, promovida por metales de transición, con la ayuda de un grupo director, se ha convertido en una alternativa muy atractiva a las tradicionales reacciones de acoplamiento cruzado. El desarrollo de este campo ha estado dominado por el empleo de catalizadores de metales nobles. Sin embargo, en los últimos años, catalizadores de metales más baratos y abundantes, como el cobalto, se han convertido en una alternativa muy interesante. Dentro de este contexto, el uso de complejos de Cp*CoIII ha recibido especial atención debido a su capacidad para promover a una gran variedad de reacciones de formación de enlaces C–C y C–X. A pesar de los avances realizados, estos sistemas aún están en su infancia en comparación con los catalizadores de Rh y Pd, debido a la falta de conocimiento fundamental. El estudio sobre la naturaleza de las especies reactivas o el mecanismo implicado en estas transformaciones se ha visto obstaculizado por la dificultad de detectar intermedios de reacción. Intrigados por esta problemática, en esta tesis doctoral hemos explorado: i) el desarrollo de nuevas estrategias para acceder a estos intermedios de reacción; ii) el uso de estos metalaciclos de Cp*CoIII, no sólo para obtener información mecanísitica sobre diferentes reacciones catalizadas por estos compuestos, sino también para mejorar su eficiencia; y finalmente, iii) el estudio del efecto de la adición de algunos aditivos en las etapas elementales involucradas en los ciclos catalíticos. El conocimiento fundamental generado durante esta tesis doctoral ha supuesto un gran avance en la catálisis de cobalto, especialmente a nivel molecular.The conversion of ubiquitous and typically inert C–H bonds into C–C and C–heteroatom bonds is one of the most attractive transformation in organic chemistry. Among the different strategies developed over the past decades, ligand-directed transition-metal-catalyzed transformations have achieved remarkable progress, becoming an attractive alternative to traditional cross-coupling reactions. During decades, these catalytic systems required noble transition metals for the efficient construction of organic molecules. However, in the past few years, more cost-effective first-row metals, such as cobalt, have emerged as an appealing alternative to precious metals. In this context, the employment of Cp*CoIII complexes have represented a tremendous advance in cobalt catalysis, since they have the potential to promote a wide variety of C–C and C–heteroatom bond-forming reactions, via putative cyclometalated cobalt(III) species. Despite this significant progress, these cobalt systems are still at their infancy compared to Rh- or Pd-based ones, essentially due to the limited fundamental organometallic understanding of these systems. The investigation of the underlying reaction mechanisms of these transformations has been hampered by the difficulty to detect/isolate key intermediates. Challenged by the lack of fundamental knowledge of these transformations, in this Doctoral thesis we explore: i) the design and development of novel synthetic routes for accessing well-defined and stable cobalt metallacycles, analogous to proposed key reactive intermediates; ii) the employment of these Cp*CoIII metallacycles not only for unravelling previous inaccessible mechanistic intricacies of selected Cp*CoIII-catalyzed processes but also for improving their efficiency; and finally, iii) the participation and/or effect of some additives in different benchmark transformations. The fundamental knowledge generated during this Doctoral Thesis has led to important breakthroughs in cobalt catalysis, specially at molecular level

Impact of the first wave of the SARS-CoV-2 pandemic on the outcome of neurosurgical patients: A nationwide study in Spain

Objective To assess the effect of the first wave of the SARS-CoV-2 pandemic on the outcome of neurosurgical patients in Spain. Settings The initial flood of COVID-19 patients overwhelmed an unprepared healthcare system. Different measures were taken to deal with this overburden. The effect of these measures on neurosurgical patients, as well as the effect of COVID-19 itself, has not been thoroughly studied. Participants This was a multicentre, nationwide, observational retrospective study of patients who underwent any neurosurgical operation from March to July 2020. Interventions An exploratory factorial analysis was performed to select the most relevant variables of the sample. Primary and secondary outcome measures Univariate and multivariate analyses were performed to identify independent predictors of mortality and postoperative SARS-CoV-2 infection. Results Sixteen hospitals registered 1677 operated patients. The overall mortality was 6.4%, and 2.9% (44 patients) suffered a perioperative SARS-CoV-2 infection. Of those infections, 24 were diagnosed postoperatively. Age (OR 1.05), perioperative SARS-CoV-2 infection (OR 4.7), community COVID-19 incidence (cases/10 5 people/week) (OR 1.006), postoperative neurological worsening (OR 5.9), postoperative need for airway support (OR 5.38), ASA grade =3 (OR 2.5) and preoperative GCS 3-8 (OR 2.82) were independently associated with mortality. For SARS-CoV-2 postoperative infection, screening swab test <72 hours preoperatively (OR 0.76), community COVID-19 incidence (cases/10 5 people/week) (OR 1.011), preoperative cognitive impairment (OR 2.784), postoperative sepsis (OR 3.807) and an absence of postoperative complications (OR 0.188) were independently associated. Conclusions Perioperative SARS-CoV-2 infection in neurosurgical patients was associated with an increase in mortality by almost fivefold. Community COVID-19 incidence (cases/10 5 people/week) was a statistically independent predictor of mortality. Trial registration number CEIM 20/217

Efficient C(sp3)-H carbonylation of light and heavy hydrocarbons with carbon monoxide via HAT photocatalysis in flow

Despite their abundance in organic molecules, considerable limitations still exist in synthetic methods that target the direct C-H functionalization at sp3-hybridized carbon atoms. This is even more the case for light alkanes, which bear some of the strongest C-H bonds known in Nature, requiring extreme activation conditions that are not tolerant to most organic molecules. To bypass these issues, synthetic chemists rely on prefunctionalized alkyl halides or organometallic coupling partners. However, new synthetic methods that target regioselectively C-H bonds in a variety of different organic scaffolds would be of great added value, not only for the late-stage functionalization of biologically active molecules but also for the catalytic upgrading of cheap and abundant hydrocarbon feedstocks. Here, we describe a general, mild and scalable protocol which enables the direct C(sp3)-H carbonylation of saturated hydrocarbons, including natural products and light alkanes, using photocatalytic hydrogen atom transfer (HAT) and gaseous carbon monoxide (CO). Flow technology was deemed crucial to enable high gas-liquid mass transfer rates and fast reaction kinetics, needed to outpace deleterious reaction pathways, but also to leverage a scalable and safe process