1‑Butyl-3-methyl-imidazolium Acetate as a Highly Active and Selective Organocatalyst for CO₂ Hydrosilylation: Insights into the Reaction Mechanism

Valorization of CO2 as a C1 synthon for synthesizing value-added chemicals and polymers reduces the emissions of this greenhouse gas in the atmosphere and paves the way to new synthetic routes in sustainable chemistry. In this contribution, the commercially available ionic liquid 1-butyl-3-methyl imidazolium acetate [BMIm][Ac] has been successfully tested as an organocatalyst in CO2 hydrosilylation to produce formoxysilane in moderate to good yields under a very low catalyst loading (0.1 mol %). The 1H, 13C, and 29Si NMR spectroscopy monitoring of CO2 reduction in the presence of a stoichiometric amount of dimethylphenylsilane (Me2PhSiH) allowed identifying the anionic pentacoordinate organosilicon species [Me2PhSi(OCHO)(Ac)]− resulting from the nucleophilic attack of the acetate anion to the silane, determining the activation of the hydride transfer from the silicon atom to CO2; this species was characterized by 29Si NMR spectroscopy and identified in the negative electrospray ionization mass spectrometry (ESI-MS) spectrum of the reaction mixture. The kinetic investigation of the reaction pathway, combined with density functional theory (DFT) modeling, corroborated this mechanistic hypothesis and contributed to shed light on the reaction mechanism

Elementos para uma história da neuroascese Elements for a history of neuroascese

O espetacular progresso das neurociências e o intenso processo de popularização, via mídia, de imagens e informações que associam a atividade cerebral a praticamente todos os aspectos da vida produzem, no imaginário social, crescente percepção do cérebro como detentor das propriedades e autor das ações que definem o que é ser alguém. Nesse contexto sociocultural, aumenta o interesse pela neuroascese, isto é, discursos e práticas a respeito de como agir sobre o cérebro para maximizar sua performance. Com o objetivo de traçar alguns elementos da história da ascese cerebral, resgatam-se momentos históricos do século XIX em que práticas neuroascéticas eram comuns. O artigo problematiza a continuidade dessas práticas na atualidade, levando em conta os diferentes contextos socioculturais e históricos nos quais se originam.<br>The spectacular progress of the neurosciences, as well as the intense process of popularization by the media of images and information that associate cerebral activity with practically every aspect of life, have produced a growing perception of the brain as the site and agent of all the properties and actions that define us as human beings. Today's socio-cultural context has seen increased interest in 'neuroascese', that is, discourses and practices aimed at maximizing brain performance. Tracing elements of the history of 'brain ascese' back to historical moments of the nineteenth century in which neuroascetic practices were commonplace, the article examines their continued use today, taking into account the social, cultural, and historical contexts in which they originated