Impact of Backbone Substitution on Organocatalytic Activity of Sterically Encumbered NHC in Benzoin Condensation.

In this study, we provide a theoretical explanation for the experimentally observed decrease in the organocatalytic activity of -aryl imidazolylidenes methylated at the C4/5-H positions in the benzoin condensation of aromatic aldehydes. A comparative quantum chemical study of energy profiles for the NHC-mediated benzoin condensation of furfural has revealed a high energy barrier to the formation of the IPr-based furanic Breslow intermediate that can be attributed to the negative steric interactions between the imidazole backbone methyl groups and -aryl substituents.

Adaptive carbonyl umpolung involving a carbanionic carbene Breslow intermediate: an alternative mechanism for NHC-mediated organocatalysis.

Herein, we propose a novel mechanistic model for NHC-mediated carbonyl umpolung which involves the formation of a carbanionic carbene Breslow intermediate (CCBI). We have demonstrated theoretically that this reactive intermediate can be formed by inserting an aldehyde into the C4-H position of an -aryl-substituted imidazolium-derived NHC the generation of an H-bonded ditopic carbanionic NHC (NHC). Our DFT study on benzoin condensation has revealed that the mechanism of polarity inversion proceeding through the CCBI may be more energetically favorable than the classical mechanism of umpolung that uses the C2 carbene position in NHC.

[New trends in age and aging research in the post-pandemic period (research overview).].

The pandemic of coronavirus infection and the general uncertainty and variability of the post-pandemic world developing with it have called into question the already outdated concept of chronological determination of the age of the older. Within the framework of this review, analyzing the latest publications on social policy, the sociology of aging, the role of information technology in the lives of older people and their employment, using the method of thematic analysis, we consider how researchers consider the transformation of the meanings of age and the characteristics of aging in the post-pandemic period. Based on the thematic analysis of articles for the period from January 2022 to March 2023, a conclusion was made about the blurring of the previous age boundaries.

The Nature of Ferromagnetism in a System of Self-Ordered α-FeSi Nanorods on a Si(111)-4° Vicinal Surface: Experiment and Theory.

In this study, the appearance of magnetic moments and ferromagnetism in nanostructures of non-magnetic materials based on silicon and transition metals (such as iron) was considered experimentally and theoretically. An analysis of the related literature shows that for a monolayer iron coating on a vicinal silicon surface with (111) orientation after solid-phase annealing at 450-550 °C, self-ordered two-dimensional islands of α-FeSi displaying superparamagnetic properties are formed. We studied the transition to ferromagnetic properties in a system of α-FeSi nanorods (NRs) in the temperature range of 2-300 K with an increase in the iron coverage to 5.

[E-health and online health communities in the daily lives of older rural residents during the pandemic.].

The situation of the COVID-19 pandemic has once again reminded of the need to use telemedicine and online health communities, especially in areas where there are not enough places in local hospitals or there are problems with obtaining quality medical care, such as rural areas where rural medicine is focused on treatment of emergency diseases and doctors have difficulties with the possibility of treatment, as well as explaining about the new coronavirus infection to patients and how this disease can be treated. In this case, online health communities provide an opportunity to find out the necessary information, as well as communicate with specialists who know the features of the new coronavirus and can give the necessary advice. Using the example of in-depth interviews with older people from villages in the Leningrad Region and the Republic of Karelia, the article examines the role of telemedicine for older people and communication in online health communities in the context of overcoming loneliness and isolation that exist in rural areas.