An Iron-Catalyzed Bond-Making/Bond-Breaking Cascade Merges Cycloisomerization and Cross-Coupling Chemistry

Treatment of readily available enynes with alkyl-Grignard reagents in the presence of catalytic amounts of Fe(acac)3 engenders a remarkably facile and efficient reaction cascade that results in the net formation of two new C−C bonds while a C−Z bond in the substrate backbone is broken. Not only does this new manifold lend itself to the extrusion of heteroelements (Z=O, NR), but it can even be used for the cleavage of activated C−C bonds. The reaction likely proceeds via metallacyclic intermediates, the iron center of which gains ate character before reductive elimination occurs. The overall transformation represents a previously unknown merger of cycloisomerization and cross-coupling chemistry. It provides ready access to highly functionalized 1,3-dienes comprising a stereodefined tetrasubstituted alkene unit, which are difficult to make by conventional means

Formal Total Synthesis of Kendomycin by Way of Alkyne Metathesis/Gold Catalysis

In an attempt to study the ability of the latest generation of alkyne metathesis catalysts to process sterically hindered substrates, two different routes to the bacterial metabolite kendomycin (1) were explored. Whereas the cyclization of the overcrowded arylalkyne 39 and related substrates turned out to be impractical or even impossible, ring closure of the slightly relaxed diyne 45 was achieved in excellent yield under notably mild conditions with the aid of the molybdenum alkylidyne 2 endowed with triphenylsilanolate ligands. The resulting cycloalkyne 46 was engaged into a gold-catalyzed hydroalkoxylation, which led to benzofuran 47 that had already previously served as a late-stage intermediate en route to 1

Hydroxy-Directed Ruthenium-Catalyzed Alkene/Alkyne Coupling: Increased Scope, Stereochemical Implications, and Mechanistic Rationale

The recognition of the dual binding mode of propargyl and allyl alcohols to [Cp*Ru] fragments fostered the development of a highly regioselective intermolecular Alder-ene-type reaction of alkynes with 1,2-disubstituted alkenes. The increased substrate scope opens new perspectives in stereochemical terms. As the loaded catalyst is chiral-at-metal, stereochemical information is efficiently relayed from the propargylic site to the emerging C−C bond. This interpretation is based on the X-ray structure of the first Cp*Ru complex carrying an intact enyne ligand, and provides valuable insights into bonding and activation of the substrates. Computational data draw a clear picture of the principles governing regio- and stereocontrol

Stabilization of a Chiral Dirhodium Carbene by Encapsulation and a Discussion of the Stereochemical Implications

For the first time, the stereochemical course of an asymmetric cyclopropanation can be discussed on the basis of experimental structural information on a pertinent chiral dirhodium carbene intermediate. Key to success was the formation of racemic single crystals of a heterochiral [Rh2{(S*)-PTTL}4{=C(Ar)COOMe}][Rh2{(R*)-PTTL}4] (Ar=MeOC6H4; PTTL=N-phthaloyl-tert-leucinate) capsule, which has been characterized by X-ray diffraction. NMR spectroscopic data confirm that the obtained structural portrait is also relevant in solution and provide additional information about the dynamics of this species. The chiral binding pocket is primarily defined by the conformational preferences of the N-phthaloyl-protected amino acid ligands and reinforced by a network of weak interligand interactions that get stronger when chlorinated phthalimide residues are used

Formation of Ruthenium Carbenes by gem-Hydrogen Transfer to Internal Alkynes: Implications for Alkyne trans-Hydrogenation

Insights into the mechanism of the unusual trans-hydrogenation of internal alkynes catalyzed by {Cp*Ru} complexes were gained by para-hydrogen (p-H2) induced polarization (PHIP) transfer NMR spectroscopy. It was found that the productive trans-reduction competes with a pathway in which both H atoms of H2 are delivered to a single alkyne C atom of the substrate while the second alkyne C atom is converted into a metal carbene. This “geminal hydrogenation” mode seems unprecedented; it was independently confirmed by the isolation and structural characterization of a ruthenium carbene complex stabilized by secondary inter-ligand interactions. A detailed DFT study shows that the trans alkene and the carbene complex originate from a common metallacyclopropene intermediate. Furthermore, the computational analysis and the PHIP NMR data concur in that the metal carbene is the major gateway to olefin isomerization and over-reduction, which frequently interfere with regular alkyne trans-hydrogenation

Increasing the Structural Span of Alkyne Metathesis

A new generation of alkyne metathesis catalysts, which are distinguished by high activity and an exquisite functional group tolerance, allows the scope of this transformation to be extended beyond its traditional range. They accept substrates that were previously found problematic or unreactive, such as propargyl alcohol derivatives, electron-deficient and electron-rich acetylenes of various types, and even terminal alkynes. Moreover, post-metathetic transformations other than semi-reduction increase the structural portfolio, as witnessed by the synthesis of a annulated phenol derivative via ring-closing alkyne metathesis (RCAM) followed by a transannular gold-catalyzed Conia-ene reaction. Further examples encompass a post-metathetic transannular ketone–alkyne cyclization with formation of a trisubstituted furan, a ruthenium-catalyzed redox isomerization, and a Meyer–Schuster rearrangement/oxa-Michael cascade. These reaction modes fueled model studies toward salicylate macrolides, furanocembranolides, and the cytotoxic macrolides acutiphycin and enigmazole A; moreover, they served as the key design elements of concise total syntheses of dehydrocurvularin (27) and the antibiotic agent A26771B (36)

Perfil de competências do enfermeiro em funções na emergência pré-hospitalar

O conceito de competência é amplamente discutido e aplicado em áreas como a formação e o apoio à gestão, no entanto a opinião acerca deste conceito não reúne consenso entre os especialistas. No campo da Emergência Pré-Hospitalar além de muito escassos os estudos, não existe qualquer ferramenta específica para a sua avaliação. O objetivo deste trabalho foi definir um perfil de competências ideal do Enfermeiro de Emergência Pré-Hospitalar e perceber de que forma os Enfermeiros que desempenham (ou desempenharam) funções nesta área se identificam com esse perfil. Desenvolveu-se um estudo correlacional, em que os dados foram recolhidos através de um questionário de autopreenchimento numa amostra de Enfermeiros que desempenham, ou desempenharam, funções na Emergência Pré-Hospitalar, mais propriamente na Viatura Médica de Emergência e Reanimação (VMER). Nos resultados destacamos a construção e validação de três escalas, utilizando para isso o Perfil de Competências definido por Malta (2016): Avaliação, Monitorização e Execução de Técnicas ao Doente em Situação Crítica (AMETDSC); Interpretação de dados e tomada de decisão em situação de pessoa em situação crítica e/ou situação de exceção (IDTDSPSC/SE); Identificação e gestão de fatores de mal-estar (IGFME). Foi também realizado um cruzamento entre os dados obtidos pelas escalas com os dados sociodemográficos com vista a estabelecer um relacionamento entre a forma como os Enfermeiros se identificam com as Competências definidas e as suas características pessoais. Observámos que de uma forma geral os Enfermeiros identificam-se com as competências do estudo de Malta (2016) que foram selecionadas para este estudo, obtendo pontuações médias superiores a 3 valores numa escala de 1 a 4. Observámos também que enquanto as variáveis género, estado civil e habilitações literárias parecem ter pouca influência na identificação com as competências estudadas, o mesmo já não se pode dizer das variáveis idade, experiência profissional genérica e experiência profissional específica que parecem exercer maior influência na forma como os Enfermeiros se identificam com estas Competências