The simplest Diels-Alder reactions are not: Endo -selective

There is a widespread perception that the high level of endo selectivity witnessed in many Diels-Alder reactions is an intrinsic feature of the transformation. In contrast to expectations based upon this existing belief, the first experimental Diels-Alder reactions of a novel, deuterium-labeled 1,3-butadiene with commonly used mono-substituted alkenic dienophiles (acrolein, methyl vinyl ketone, acrylic acid, methyl acrylate, acrylamide and acrylonitrile) reveal kinetic endo:exo ratios close to 1:1. Maleonitrile, butenolide, α-methylene γ-butyrolactone, and N-methylmaleimide behave differently, as does methyl vinyl ketone under Lewis acid catalysis. CBS-QB3 calculations incorporating solvent and temperature parameters give endo:exo product ratios that are in near quantitative agreement with these and earlier experimental findings. This work challenges the preconception of innate endo-selectivity by providing the first experimental evidence that the simplest Diels-Alder reactions are not endo-selective. Trends in behaviour are traced to steric and electronic effects in Diels-Alder transition structures, giving new insights into these fundamental processes.This work was supported by the Australian Research Council (DP160104322). MNP-R acknowledges that the computational component of this research was undertaken with the assistance of resources provided at the NCI National Facility through the National Computational Merit Allocation Scheme supported by the Australian Government

Особенности оценки профессиональных рисков в медицинской организации

Работа посвящена оценки профессионального риска для работников медицинских организаций с учетом эпидемиологической обстановки. В данной работе рассмотрено нормативно-правовое регулирование оценки профессионального риска в Российской Федерации. Проведен анализ существующих методов оценки профессионального риска. В результате исследования проведена оценка профессионального риска для работников медицинской организации и предложены мероприятия по уменьшению уровня риска.The work is devoted to the assessment of professional risk for employees of medical organizations, taking into account the epidemiological situation. This paper examines the legal regulation of professional risk assessment in the Russian Federation. The analysis of existing methods of professional risk assessment is carried out. As a result of the study, an assessment of professional risk for employees of a medical organization was carried out and measures to reduce the level of risk were proposed

Triplet energy management between two signaling units through cooperative rigid scaffolds

[EN] Through-bond triplet exciplex formation in donor-acceptor systems linked through a rigid bile acid scaffold has been demonstrated on the basis of kinetic evidence upon population of the triplet acceptors (naphthalene, or biphenyl) by through-bond triplet-triplet energy transfer from benzophenone.Financial support from the Spanish Government (Grants SEV-2012-0267, CTQ2012-38754-C03-03, CTQ2013-47872-C2-1-P and JCI-2011-09926), EU (PCIG12GA-2012-334257), Generalitat Valenciana (Prometeo Program), and Technical University of Valencia (VLC/Campus, ASIC-UPV for computational facilities and Predoctoral FPI fellowship for P. Miro) is gratefully acknowledged.Miró Richart, P.; Vayá Pérez, I.; Sastre Navarro, GI.; Jiménez Molero, MC.; Marín García, ML.; Miranda Alonso, MÁ. (2016). Triplet energy management between two signaling units through cooperative rigid scaffolds. Chemical Communications. 52(4):713-716. https://doi.org/10.1039/c5cc08102eS71371652