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New methodologies in asymmetric allylic substitution and organocascade reactions
No full textAsymmetric organocatalysis and organometallic catalysis are rapidly developing. The first catalytic process can be traced back in the XIX century. Since then, research in the field of catalysis grew, especially in the last decades exponentially. Four projects involving organocatalysis are described in this thesis: “Highly enantioselective addition of anthrones to MBH-carbonates”, “Synergistic catalysis: Highly diastereoselective benzoxazole addition to Morita-Baylis-Hillman carbonates”, “Three-component diastereoselective cascade synthesis of thiohydantoins” and “Highly diastereoselective synthesis of spiropyrazolones”.A) Asymmetric allylic substitutionSince Tsuji and Trost reported their first examples of allylic substitution catalysed by palladium salts in 1963, many examples of allylic substitution were published involving other types of transition metals. Later, in 2002, Kim et al. reported the first allylic substitution using a metal-free approach.Morita-Baylis-Hillman carbonates are important scaffolds in the synthesis of more complex molecules due to the presence of numerous functional groups.In this thesis two examples of asymmetric allylic substitution involving Morita-Baylis-Hillman (MBH) carbonates are described.Highly enantioselective addition of anthrones to Morita-Baylis-Hillman carbonatesAnthrone derivatives are present in various natural sources and are known for their medicinal effects. We were interested in the enantioselective addition of anthrone to MBH-carbonates. The products were synthesised in very good yields and enantioselectivity by using a (DHQD)2AQN as catalyst. Moreover, a kinetic resolution was perfomed in order to better understand the mechanistic process.Synergistic catalysis: Highly diastereoselective benzoxazole addition to Morita-Baylis-Hillman carbonatesCatalysis is one of the most efficient strategies for identifying new chemical reactions. Usually, a catalytic pathway relies on the interaction of a single catalyst with a single reagent in order to lower the energetic barrier. In some cases, the mono-catalytic concept is not enough and other strategies are used, in particular, synergistic catalysis. This consists in the activation of the electrophile and the nucleophile by two different catalysts for reaction to occur. Based on this idea, we studied the addition of benzoxazoles to Morita-Bayllis-Hillman carbonates by the use of two different catalysts (Metal Lewis acid and Organic Lewis base). Both catalysts work in a concerted way giving the final compound in high yield and diastereoselectivity.B) Organocascade reactionsSynthesis of complex organic molecules is a challenge for every chemist. The aim is achieveing the final product in as few steps as possible using safer, cleaner and environmentally friendly techniques. One-pot reactions emerged as a powerful tool in creating several bonds in one step. Based on this idea, we studied two reactions:Three-component diastereoselective cascade synthesis of thiohydantoinsThiohydantoins have interesting medicinal applications such as antibacterial, antiviral, antimutagenic, etc. Synthesising these scaffolds in one step via three-component one-pot reaction was our main focus. We developed a three-component cascade reaction for the synthesis of thiohydantoins. The reaction between ?-amino esters, nitrostyrenes and aromatic isothiocyanates is efficiently promoted by organic bases to afford highly substituted thiohydantoins in moderate to good yields and diastereoselectivities.Highly diastereoselective synthesis of spiropyrazolonesSpiro compounds are present in various natural products and are powerful active agents. We have developed a methodology for the synthesis of spiropyrazolone bearing fourchiral centres. The reaction was catalysed by a secondary amine ina Michael-aldol cascade fashion affording the product in very good yields and diastereoselectivity
Organocatalytic fluoromalonate addition to tetrahydroisoquinolines through a CDC process
No full textRecently green chemistry has attracted much attention from organic chemists due the problems that our society faces in terms of waste generation and energy consumption. For this reason cross dehydrogenative couplings (CDC) have emerged as one of the most important strategies for C?C bond formation nowadays. In our research group, enticed by the use of organocatalytic cross dehydrogenative coupling reactions and in the synthesis of fluorinated compounds, we developed a new organocatalytic methodology based on the CDC activation of tetrahydroisoquinolines followed by addition of fluoromalonates. The reaction is simply catalyzed by organic dyes (Rose Bengal) using green LED as a light source and oxygen as stoichiometric oxidant and let us to obtain the final fluorinated compounds in good yields
Highly diastereoselective synthesis of spiropyrazolones
No full textWe report a highly diastereoselective synthesis of spiropyrazolones catalyzed by secondary amines. The reported Michael-Aldol cascade reaction affords the desired spiropyrazolones bearing four chiral centers as a single diastereomer in excellent yields
Synergistic catalysis: highly diastereoselective benzoxazole addition to Morita–Baylis-Hillman carbonates
Get PDFAn expedited method has been developed for the diastereoselective synthesis of highly functionalized alkyl-azaarene systems with good yields and high diastereoselectivities (>15 : 1 dr). The methodology includes a synergistic catalysis event involving organometallic (10 mol% AgOAc) activation of an alkyl azaarene and Lewis base (10 mol% DABCO) activation of a Morita–Baylis–Hillman carbonate. The structure and relative configuration of a representative product were confirmed by X-ray analysis
Three-component diastereoselective cascade synthesis of thiohydantoins
No full textA new three-component cascade reaction for the synthesis of thiohydantoins is reported. The reaction between ?-amino esters, nitrostyrenes, and aromatic isothiocyanates is efficiently promoted by organic bases to afford highly substituted thiohydantoins in moderate to good yields and diastereoselectivities.<br/
Studiul și cercetarea privind măsurarea și monitorizarea emisiilor de gaze și poluarea fonică în domeniul transporturilor
No full textFişierul ataşat conţine: Rezumat, Cuprins, Introducere, Sursele bibliografice.Principala direcție de studiu a tezei constă în arătarea situației actuale și situației anterioare înregistrată în formă de stratistică care arată cît de rea este starea mediului înconjurător în urma activității sectorului transporturilor.
1.Аnalizа impactului activității sectorului transporturilor asupra mediului înconjurător și în special asupra Repulicii Moldova
Activitatea omului din an în an devine tot mai intensă pe tot globul pămîntesc și țara noastră nui o excepție, și analizînd impactul scestei activități asupra mediului ajungem la concluzia că cel mai importatnt sector din activitatea omenirii este sectorul transporturilor auto care ne garantează o mobilitate înaltă și economisirea timpului fiecărei persoane. Fără nici o îndoială acest sector aduce multe beneficii dar în același timp si daune enorme mediului și ecosistemului inclusiv și în Republica Moldova. Deci în acest compartiment a fost redat în detalii impactul activității sectorului transportului asupra mediului.
2.Studiul și cercetarea privind măsurarea și monitorizarea emisiilor de gaze în urma activității sectorului transporturilor
Studiul infrastructurii și funcționării transportului urban ca factor generator de emisii cu im-pact asupra ecosistemelor din mun. Chișinău; Stabilirea cotei transportului auto, caracteristica canti-tativă și calitativă a emisiilor gazelor de eșapament și impactul asupra sănătății omului; Relevarea datelor privind emisiile traficului auto pe principalele artere rutiere ale or. Chișinău.
3.Rezultatele modelării influienței emisiilor auto asupra unor specii de plante vasculare și inferioare
S-a realizat monitoringul zonelor poluate cu emisii auto în baza parametrilor fiziologici și biochimici în frunzele unor specii de arbori. A fost stabilit impactul unor factori de stres (emisii auto) asupra productivității biologice a vegetației. S-a demonstrat că, răspunsurile fiziologice ale plantelor, determinate în baza parametrilor fizio-biochimici, pot servi ca indicator la poluare.The main direction of study of the thesis is to show the current situation and the previous situation recorded in the form of a strategy that shows how bad the state of the environment is following the activity of the transport sector.
1.Analysis of the impact of the activity of the transport sector on the environment and in particular on the Republic of Moldova
Human activity is becoming more intense every year around the globe and our country is no exception, and analyzing the impact of this activity on the environment we conclude that the most important sector of human activity is the car transport sector which guarantees high mobility and saving each person time. Undoubtedly, this sector brings many benefits but at the same time enormous damage to the environment and the ecosystem, including the Republic of Moldova. So in this section the impact of the activity of the transport sector on the environment was reported in detail.
2.Study and research on the measurement and monitoring of gaseous emissions from the activity of the transport sector
Study of the infrastructure and functioning of urban transport as a factor generating emissions with impact on ecosystems in Chisinau; Establishing the share of car transport, the quantitative and qualitative characteristic of exhaust emissions and the impact on human health; Revealing the data regarding the car traffic emissions on the main road arteries of the town. Chisinau.
3.The results of modeling the influence of car emissions on some species of vascular and inferior plants
The monitoring of the areas polluted with car emissions was performed based on the physiological and biochemical parameters in the leaves of some tree species. The impact of stressors (car emissions) on the biological productivity of vegetation has been established. It has been shown that the physiological responses of plants, determined on the basis of physio-biochemical parameters, can serve as an indicator of pollution
Structura traficului auto dintre Republica Moldova - Uniunea Europeana și optimizarea proceselor de transport și logistică din cadrul sectorului dat, identificarea problemelor principale
Get PDFFișierul atașat conține: Rezumat, Cuprins, IntroducereDirecţia principală de studiu a tezei constă în aprecierea situaţiei actuale şi a posibilităţilor
investiţionale, cercetarea factorilor de influenţă în realizarea procesului de transport, necesitatea
utilizării tehnologiilor inovaţionale, prognozarea complexă a fluxului de transport, cît şi
evidenţierea căilor efective cu asigurare de infrastructură de drum şi logistică.Din analiza efectuată de autori, în acest studiu, se desprind unele tconcluzii teoretice și prac tice. În această ordine de idei, se constată că trebuie depuse eforturi comune pentru atingerea tuturor
scopurilor. Cercetările strategice sunt necesare în vederea stabilirii exacte a segmentului de piaţă pe
care întreprinderea îl va exploata. Prognozarea fluxului de transport permite prestabilirea resurselor
şi mijloacelor necesare, iar găsirea căilor efective cu asigurare de infrastructură de drum şi logistică
va permite minimizarea consumului resurselor şi utilizării mijloacelor.The main study direction of the thesis consists in assessing the current situation and in vestment possibilities, researching the factors influencing the transport process, the need to use
innovative technologies, complex forecasting of the transport flow, as well as highlighting the
effective ways to ensure road infrastructure. logistics. From the analysis performed by the authors, in this study, some theoretical and practical
conclusions can be drawn. In this regard, it is stated that joint efforts must be made to achieve all
goals. Strategic research is needed to determine the exact market segment that the company will
operate. The forecast of the transport flow allows the pre-establishment of the necessary re sources and means, and the finding of the effective ways with the provision of road infrastructure
and logistics will allow the minimization of the consumption of resources and the use of means
Synergistic catalysis: enantioselective addition of alkylbenzoxazoles to enals
No full textA novel catalytic enantioselective methodology based on synergistic catalysis is reported. The strategy involves: 1)?the metal-Lewis-acid activation of alkylazaarenes, and 2)?the secondary-amine activation of enals. Consequently, highly functionalized chiral alkylazaarenes were obtained in good yields and with reasonable stereoselectivit
Expanding the scope of metal-free enantioselective allylic substitutions: Anthrones
No full textThe highly enantioselective asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates with anthrones is presented. The reaction is simply catalyzed by cinchona alkaloid derivatives affording the final alkylated products in good yields and excellent enantioselectivities
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