ultrasound mediated synthesis of ecofriendly zinc chalcogenates in on water conditions

Nucleophilic Selenium is a convenient strategy for the functionalization of organic substrates having electrophilic character. Among all the methods developed for their preparation, the reduction of the corresponding diselenides represents the most versatile procedure. Using these protocols selenolates were usually prepared in situ using atom expensive reducing agents such as NaBH4, LiAlH4, or metals (Na, Li) or metal hydride (NaH). We recently reported that zinc can be efficiently used to reduce Se-halogen bond affording bench stable regents such as PhSeZnCl that showed a strong rate acceleration in "on water" conditions for a number of reactions: alkyl, aryl, vinyl and acyl substitutions, ring-opening reactions of epoxides and aziridines and Michael type addition. We report now the use of Ultrasound irradiation for the oxidative insertion of zinc into Se-Se bond and the formation of the nucleophilic reagent PhSeZnSePh as a green strategy to avoid the use of useless halogen and increase the atom economy of the selenenylating species

Ultrasound-accelerated synthesis of thioesters through the Ag(I)-catalyzed decarboxylative coupling between α-keto acids and diorganyl disulfides, under mild reaction conditions

Here is reported a new, green method to obtain thioesters, using available and ecofriendly starting materials, as -keto acids and an alternative energy source, the ultrasound. The title compounds 3a-3i were prepared in moderate to good yields, through the reaction between glyoxylic acids as acyl transfer agents and diorganyl disulfides, in the presence of AgNO3 as catalyst, K2S2O8 as an oxidant and a mixture of DMSO/H2O as the solvent, in 20 minutes under sonication. In addition, it was performed the chemical modification of chitosan (Cs) 4 with the aim of preparing new biopolymers 6a-6d with improved antifungal and antibacterial properties. The presence of the amine groups in its backbone allows the formation of Schiff bases by reacting them with aldehydes. In this work the aldehyds used were citronellal 5a, citral 5b, -phenylseleno-citronellal 5c and 3-phenylthio- citronellal 5d.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESNo presente trabalho foi desenvolvido um novo método alternativo para a obtenção de tioésteres, utilizando materiais de partida acessíveis e ecológicos, como -ceto ácidos, e ultrassom como fonte de energia alternativa. Os compostos 3a-3j foram obtidos com rendimentos entre bons e moderados, através da reação entre ácidos glioxílicos como agentes de transferência de acila e dissulfetos de diorganoíla, na presença de AgNO3 como catalisador, K2S2O8 como oxidante e uma mistura de DMSO/H2O como solvente, em 20 minutos sob sonicação.Adicionalmente, foi realizada a modificação química da quitosana 4 para formar diferentes materiais poliméricos 6a-6d com o objetivo de aumentar suas propriedades antifúngica e antibacteriana. A presença de grupos amina no seu esqueleto permitiu a formação de bases de Schiff após a reação com aldeídos. Os aldeídos usados foram citronelal 5a, citral 5b, -fenilselenocitronelal 5c e 3- feniltiocitronelal 5d

Il «global turn» e la storia dell'Asia

2siThe essay analyzes critically the impact of the global turn on the evolution of the studies on Asian history. After a brief introduction, which discusses how the history of Asia has struggled to overcome the periodization focused on European activities, the essay articulates into two parts. The first, by Diego Abenante, analyzes the evolution of the historiography on South Asia, with an emphasis on the more recent historiographic trends that emerged between the late 1990s and the early 2000s. The second part of the essay, by Laura De Giorgi, offers a brief overview of the impact of the global turn in the field of East Asian history. The authors elaborate on the importance of the global turn in weakening the insularity of the discipline, as a consequence of the deeper comprehension of the complex interplay of economic, political and cultural dynamics in the making of modern world.partially_openembargoed_20191231ABENANTE, DIEGO; DE GIORGI, LAURAAbenante, Diego; DE GIORGI, Laur

Il «global turn» e la storia dell'Asia

The essay analyzes critically the impact of the global turn on the evolution of the studies on Asian history. After a brief introduction, which discusses how the history of Asia has struggled to overcome the periodization focused on European activities, the essay articulates into two parts. The first, by Diego Abenante, analyzes the evolution of the historiography on South Asia, with an emphasis on the more recent historiographic trends that emerged between the late 1990s and the early 2000s. The second part of the essay, by Laura De Giorgi, offers a brief overview of the impact of the global turn in the field of East Asian history. The authors elaborate on the importance of the global turn in weakening the insularity of the discipline, as a consequence of the deeper comprehension of the complex interplay of economic, political and cultural dynamics in the making of modern world

Síntese fotocatalítica mediada por luz visível de oxazóis-5-carbaldeídos 2-substituídos promovida por ácido benzenos selenínico

Visto a necessidade de uma metodologia mais verde para acessar o núcleo oxazol, o objetivo deste trabalho foi a aplicação de ácido benzenosselenínico 2a, sob condições fotocatalíticas e irradiação de luz visível para a ciclização de N-propargilamidas 1a e obtenção de oxazóis-5-carbaldeídos 2-substituídos 3a

<strong>Explorative application of selenium catalysts in the oxidation of benzyl alcohol.</strong>

Oxidation mediated by hydrogen peroxide needs to be accelerate by approrpiate catalyst in order to be completed in a reasonable reaction time. As a part of our investigation in the use of organoselenium cataysts in bio-mimetic oxidative protocol we reported here some preliminary results on the oxidation of benzyl alcohol into the corresponding benzoic acid

Seleno-functionalization of quercetin improves the non-covalent inhibition of MproM^{pro} and its antiviral activity in cells against SARS-CoV-2

The development of new antiviral drugs against SARS-CoV-2 is a valuable long-term strategy to protect the global population from the COVID-19 pandemic complementary to the vaccination. Considering this, the viral main protease (Mpro) is among the most promising molecular targets in light of its importance during the viral replication cycle. The natural flavonoid quercetin 1 has been recently reported to be a potent Mpro inhibitor in vitro, and we explored the effect produced by the introduction of organoselenium functionalities in this scaffold. In particular, we report here a new synthetic method to prepare previously inaccessible C-8 seleno-quercetin derivatives. By screening a small library of flavonols and flavone derivatives, we observed that some compounds inhibit the protease activity in vitro. For the first time, we demonstrate that quercetin (1) and 8-(p-tolylselenyl)quercetin (2d) block SARS-CoV-2 replication in infected cells at non-toxic concentrations, with an IC50 of 192 μM and 8 μM, respectively. Based on docking experiments driven by experimental evidence, we propose a non-covalent mechanism for Mpro inhibition in which a hydrogen bond between the selenium atom and Gln189 residue in the catalytic pocket could explain the higher Mpro activity of 2d and, as a result, its better antiviral profile