Short Peptide-Derived Bifunctional Brønsted Base Catalysts in Asymmetric Michael Reactions/Peptido Laburretatik Eratorritako Brønsted Baseak Katalizatzaile Bifuntzional Moduan Michael Erreakzio Asimet

498 p.Peptide catalysis has proven to be an effective tool for the synthesis of enantiomerically enriched compounds with synthetic applications or that are precursors of molecules with biological and pharmacological interest. Their ability to interact through H-bonds with the substrates and form complex H-bond networks is extremely helpful for reaction stereocontrol. Likewise, asymmetric Brønsted base (BB) catalysis is also a well stablished activation protocol for a great variety of transformations, and especially interesting and effective are bifunctional BB catalysts bearing H-bond donors, which can activate the nucleophile and the electrophile at the same time. In this context, and in spite of the big progress in the realm of asymmetric catalysis, there are still many new and challenging reactions that have not been resolved and/or require improvement. So, the main goal of this Thesis has been to design and synthesize a new family of catalysts that combine a short peptide, a typical privileged H-bond donating scaffold used in organocatalysis (squaramide/ ureidoaminal) and a BB, and to investigate them in some challenging transformations involving the generation of quaternary carbon stereocenters. Figur

Wikipediaren pertzepzio eta erabilera DBH-ko ikasle eta irakasleen artean

Wikipedia is one of the most employed sources of information, since it provides free, easy, and fast access to many information topics. However, due to the collaborative developing system of Wikipedia, its reliability is often questioned. In any case, many investigations show that an active use of Wikipedia can be remarkably beneficial for the learning process and that when Wikipedia is used as an educational tool, many qualities and competencies can be acquired by students. Furthermore, using Wikipedia more actively may improve the opinions regarding its reliability. Thus, in this investigation, the perceptions, and uses of Wikipedia among students and teachers at a high school in Gipuzkoa have been studied, using two different questionnaires. According to the data, both students and teachers hold positive opinions about Wikipedia, although it seems that many of them still present trusting issues towards it. Additionally, educators do not seem to be making the most of Wikipedia’s potential as a teaching tool, since its use is essentially limited to looking up information. Therefore, in the future it would be interesting on the one hand, to scale up this research about perceptions, and on the other hand, to develop interventions that promote a more active use of Wikipedia and employ the available resources to do so.; Wikipedia informazioa bilatzeko iturririk erabilienetarikoa da, han gai desberdinei buruzko informazio ugari aurkitu daitekeelako erraz, azkar eta dohainik. Baina duen eraikuntza-sistema kolektiboaren ondorioz, Wikipediaren fidagarritasuna zalantzan jartzen dute askok. Hala ere, burututako ikerketa ugaritan ikusi da Wikipediaren erabilerak, eta bereziki kontsulta lanetara mugatzen ez den erabilera aktibo batek, ekarpen ugari eskaintzen dituela eta Wikipedia baliabide didaktiko moduan erabiliz ikasleek konpetentzia desberdinak bereganatu ditzaketela. Gainera, Wikipediaren erabilera aktiboagoa egiten denean, haren fidagarritasunari buruzko iritzia hobetu daiteke. Hortaz, azterlan honetan Gipuzkoako ikastola bateko DBHko ikasle eta irakasleen Wikipediaren pertzepzioa eta erabilera ikertu dira, bi galdetegi desberdinen bidez. Ikerketa honetatik ondorioztatu daiteke bai ikasleek eta bai irakasleek Wikipediaren iritzi positiboak dituztela oro har, baina informazio iturri honek oraindik mesfidantza sortzen duela kasu askotan. Gainera, Wikipediaren potentzial didaktikoa ez da aprobetxatzen eta haren erabilera ia kontsulta-lanetara mugatua dago. Beraz, interesgarria izan liteke, batetik, eskala handiago batean pertzepzio hauek ikertzen jarraitzea, eta bestetik, Wikipediaren erabilera aktiboagoa sustatuko duten esku hartzeak diseinatzea, eta horretarako jada existitzen diren informazio eta baliabideez baliatzea

syn-Selective Michael reaction of α-branched aryl acetaldehydes with nitroolefins promoted by squaric amino acid derived bifunctional Brønsted bases

[EN] Here we describe a direct access to 2,2,3-trisubstituted syn γ-nitroaldehydes by addition of α-branched aryl acetaldehydes to nitroolefins promoted by a cinchona based squaric acid-derived amino acid peptide. Different α-methyl arylacetaldehydes react with β-aromatic and β-alkyl nitroolefins to afford the Michael adducts in high enantioselectivity and syn-selectivity. NMR experiments and DFT calculations predict the reaction to occur through the intermediacy of E-enolate. The interaction between the substrates and the catalyst follows Pápai’s model, wherein an intramolecular H-bond interaction in the catalyst between the NH group of one of the tert-leucines and the squaramide oxygen seems to be key for discrimination of the corresponding reaction transition states.Support has been provided by the University of the Basque Country UPV/EHU (UFI QOSYC 11/22), Basque Government (GV grant IT1236-19), and Ministerio de Ciencia e Innovación (grant PID2019-109633GB-C21), Spain. A. G. and T. E. thank Basque Government and MINECO respectively for fellowships. We would like to express our gratitude to the students I. Gonzalez-Mujika and M. Campo for their participation in conducting some experiments of the reaction scope. We also thank SGIker (UPV/EHU) for providing NMR, HRMS. X-Ray and computational resources

Organocatalytic Michael Addition of Unactivated α-Branched Nitroalkanes to Afford Optically Active Tertiary Nitrocompounds

The direct, asymmetric conjugate addition of unactivated α-branched nitroalkanes is developed based on the combined use of chiral amine/ureidoaminal bifunctional catalysts and a tunable acrylate template to provide tertiary nitrocompounds in 55–80% isolated yields and high enantioselectivity (e.r. up to 96:4). Elaboration of the ketol moiety in thus obtained adducts allows a fast entry to not only carboxylic and aldehyde derivatives but also nitrile compounds and enantioenriched 5,5-disubstituted γ-lactams.We thank the Basque Government (EJ, grant IT1583-22) and Agencia Estatal de Investigación (grants PID2019-109633GB and PID2022-137153NB-C21/AEI/10.13039/501100011033) for financial support. A.G.-U. thanks EJ; B.L. thanks the Navarra Government, and M.E.-V. thanks UPNA (PJUPNA18-2022). Authors also thank SGIker (UPV/EHU/ERDF, EU) for providing NMR, HRMS, and X-ray resources

Pyrrolidin-2,3-diones as pronucleophiles in organocatalytic Michael additions to vinyl sulfones

[EN]This research project has been developed at the Department of Organic Chemistry I at the Faculty of Chemistry in San Sebastian under the guidance of professor Antonia Mielgo from the same department. The research work of this project is a continuation of previous work from the research group on the potential of pyrrolidin-2,3-diones as pronucleophiles in asymmetric organocatalysis. More specifically, in this case the goal has been the investigation of the Michael reaction of C4-substituted pyrrolidin-2,3-diones with vinyl sulfones in the presence of chiral Brønsted bases as catalysts.[EU]Ikerketa lan hau Kimika Fakultateko Kimika Organikoa I sailean garatu da, Donostin, Antonia Mielgo irakaslearen zuzendaritzapean. Proiektua ikerketa taldean garatzen ari zen pirrolidin-2,3-dionek organokatalisi asimetrikoan pronukleofilo moduan duten potentzialari buruzko lanaren jarraipena da. Zehazki, helburua binil sulfonetara C4-n ordezkatutako pirrolidin-2,3-dionen Michael adizioa ikertzea izan da, Brønsted base kiralen presentzian katalizatzaile moduan

Pyrrolidin-2,3-diones as pronucleophiles in organocatalytic Michael additions to vinyl sulfones

[EN]This research project has been developed at the Department of Organic Chemistry I at the Faculty of Chemistry in San Sebastian under the guidance of professor Antonia Mielgo from the same department. The research work of this project is a continuation of previous work from the research group on the potential of pyrrolidin-2,3-diones as pronucleophiles in asymmetric organocatalysis. More specifically, in this case the goal has been the investigation of the Michael reaction of C4-substituted pyrrolidin-2,3-diones with vinyl sulfones in the presence of chiral Brønsted bases as catalysts.[EU]Ikerketa lan hau Kimika Fakultateko Kimika Organikoa I sailean garatu da, Donostin, Antonia Mielgo irakaslearen zuzendaritzapean. Proiektua ikerketa taldean garatzen ari zen pirrolidin-2,3-dionek organokatalisi asimetrikoan pronukleofilo moduan duten potentzialari buruzko lanaren jarraipena da. Zehazki, helburua binil sulfonetara C4-n ordezkatutako pirrolidin-2,3-dionen Michael adizioa ikertzea izan da, Brønsted base kiralen presentzian katalizatzaile moduan

Progress in (Thio)urea‐ and Squaramide‐Based Brønsted Base Catalysts with Multiple H‐Bond Donors

Nowadays chiral (thio)urea- and squaramide-based Brønsted base catalysts are widely applied to enantioselective carbon-carbon and carbon-heteroatom bond forming reactions. In recent years, variations of these catalysts that incorporate and additional H-bond donor unit (green remark) have been shown to perform often superior in terms of activity and stereoselectivity. This Review covers aspects on these catalysts design and their applications.We thank the Basque Government (EJ, grant IT-1583-22) and Agencia Estatal de Investigación (grant PID2019-109633GB−C21/AEI/10.13039/501100011033), Spain, for financial support. A. G.-U. thanks EJ