Recent advances in the catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides

Catalytic asymmetric 1,3-dipolar cycloadditions of azomethine ylides have turned out to be one of the most efficient methods for the preparation of enantioenriched pyrrolidines. The past decade has witnessed the development of a bunch of well-defined catalytic systems capable of affording excellent diastereo and enantioselectivities. Recently, a great effort has been focused on expanding the scope of the cycloaddition with regard to both reaction partners. In this review, we will discuss important advances that have been reported in this area since 2011The Ministerio de Economía y Competitividad (MINECO, project CTQ2012-3579) and Consejería de Educación de la Comunidad de Madrid (programme AVANCAT; S2009/PPQ-1634

Hydroamination reactions by metal triflates: Bronsted acid vs. metal catalysis?

Catalytic hydroamination reactions involving the addition of carboxamides (X = CO), carbamates (X = CO2) and sulfonamides (X = SO2) to unactivated CC bonds are briefly reviewed. Development in this field of catalytic research is briefly charted, followed by a discussion of possible mechanisms, including arguments to support the operation of both metal and Brønsted acid catalysis in these systems. Future developments in the area are summarised. © The Royal Society of Chemistry 2010.39511711175Müller, T.E., Hultzsch, K.C., Yus, M., Foubelo, F., Tada, M., (2008) Chem. Rev., 108, p. 3795Constable, D.J.C., Dunn, P.J., Hayler, J.D., Humphrey, G.R., Leazer, J.L., Linderman, R.J., Lorenz, K., Zhang, T.Y., (2007) Green Chem., 9, p. 411Ranu, B.C., Banerjee, S., (2007) Tetrahedron Lett., 48, p. 141. , For example, seeKumar, R., Chaudhary, P., Nimesh, S., Chandra, R., (2006) Green Chem., 8, p. 356Dzhemilev, U., Tolstikov, G., Khusnutdinov, R., (2009) Russ. J. Org. Chem., 45, p. 957Quinet, C., Jourdain, P., Hermans, C., Atest, A., Lucas, I., Marko, I.E., (2008) Tetrahedron, 64, p. 1077. , See for exampleHorrillo-Martinez, P., Hultzsch, K.C., Gil, A., Branchadell, V., (2007) Eur. J. Org. Chem., p. 3311Crimmin, M.R., Arrowsmith, M., Barrett, A.G.M., Casely, I.J., Hill, M.S., Procopiou, P.A., (2009) J. Am. Chem. Soc., 131, p. 9670Hong, S., Marks, T.J., (2004) Acc. Chem. Res., 37, p. 673Walsh, P.J., Baranger, A.M., Bergman, R.G., (1992) J. Am. Chem. Soc., 114, p. 1708Müller, C., Koch, R., Doye, S., (2008) Chem.-Eur. J., 14, p. 10430Beller, M., Trauthwein, H., Eichberger, M., Breindl, C., Herwig, J., Müller, T.E., Thiel, O.R., (1999) Chem.-Eur. J., 5, p. 1306Rodriguez-Zubiri, M., Anguille, S., Brunet, J.J., (2007) J. Mol. Catal. A: Chem., 271, p. 145Bäckvall, J.E., Åkermark, B., Ljunggren, S.O., (1979) J. Am. Chem. Soc., 101, p. 2411Hahn, C., (2004) Chem.-Eur. J., 10, p. 5888. , See for exampleMotta, A., Fragala, I.L., Marks, T.J., (2006) Organometallics, 25, p. 5533Tobisch, S., (2008) Chem.-Eur. J., 14, p. 8590Aillaud, I., Collin, J., Hannedouche, J., Schulz, E., (2007) Dalton Trans., p. 5105Qian, H., Widenhoefer, R.A., (2005) Org. Lett., 7, p. 2635Karshtedt, D., Bell, A.T., Tilley, T.D., (2005) J. Am. Chem. Soc., 127, p. 12640Zhang, J., Yang, C., He, C., (2006) J. Am. Chem. Soc., 128, p. 1798Brouwer, C., He, C., (2006) Angew. Chem., Int. Ed., 45, p. 1744Giner, X., Najera, C., (2008) Org. Lett., 10, p. 2919Taylor, J.G., Whittall, N., Hii, K.K., (2005) Chem. Commun., p. 5103Taylor, J.G., Whittall, N., Hii, K.K., (2006) Org. Lett., 8, p. 3561Dias, H.V.R., Wu, J., (2008) Eur. J. Inorg. Chem., p. 509. , For a discussion of ethylene complexes ofCu(i), Ag(i) and Au(i), seeMcBee, J.L., Bell, A.T., Tilley, T.D., (2008) J. Am. Chem. Soc., 130, p. 16562Cheng, X.J., Xia, Y.Z., Wei, H., Xu, B., Zhang, C.G., Li, Y.H., Qian, G.M., Li, W., (2008) Eur. J. Org. Chem., p. 1929Rosenfeld, D.C., Shekhar, S., Takemiya, A., Utsunomiya, M., Hartwig, J.F., (2006) Org. Lett., 8, p. 4179Li, Z., Zhang, J., Brouwer, C., Yang, C.-G., Reich, N.W., He, C., (2006) Org. Lett., 8, p. 4175Wabnitz, T.C., Yu, J.Q., Spencer, J.B., (2004) Chem.-Eur. J., 10, p. 484Taylor, J.G., (2008), PhD Thesis, Imperial College LondonHuang, J.M., Wong, C.M., Xu, F.X., Loh, T.P., (2007) Tetrahedron Lett., 48, p. 3375Michaux, J., Terrasson, V., Marque, S., Wehbe, J., Prim, D., Campagne, J.M., (2007) Eur. J. Org. Chem., p. 2601Motokura, K., Nakagiri, N., Mori, K., Mizugaki, T., Ebitani, K., Jitsukawa, K., Kaneda, K., (2006) Org. Lett., 8, p. 4617Yang, L., Xu, L.W., Xia, C.G., (2008) Tetrahedron Lett., 49, p. 2882Kovacs, G., Ujaque, G., Lledos, A., (2008) J. Am. Chem. Soc., 130, p. 853Dorta, R., Egli, P., Zurcher, F., Togni, A., (1997) J. Am. Chem. Soc., 119, p. 10857Hartwig, J.F., (2004) Pure Appl. Chem., 76, p. 507. , These were shown to proceed via allylpalladium(ii) intermediates, see, and references thereinJohns, A.M., Sakai, N., Ridder, A., Hartwig, J.F., (2006) J. Am. Chem. Soc., 128, p. 9306Zhang, Z., Lee, S.D., Widenhoefer, R.A., (2009) J. Am. Chem. Soc., 131, p. 5372Anastas, P., Warner, J., (1998) Green Chemistry: Theory and Practice, , Oxford University Press, New Yor

Harga, Pembentukan Harga dan Keseimbangan Pasar

Seperti yang kita ketahui bahwa ekonomi takkan pernah lepas dari kata menjual, membeli, harga, dan mendapatkan keuntungan. Pasar adalah tempat bertemunya penjual dan pembeli yang sudah sepakat dengan harga yang ditawarkan. Harga adalah bentuk atau nilai sejumlah uang yang harus dibayarkan oleh seorang pembeli atau konsumen atas barang atau jasa yang sudah ia dapatkan dari penjual atau produsen. Harga pasar adalah tinggi rendahnya harga suatu barang yang terjadi atas kesepakatan produsen dengan konsumen. Sebelum terjadinya harga pasar, dimulai proses penetapan harga pasar. Yang ikut andil dalam penetapan harga pasar adalah para pelaku ekonomi, baik produsen maupun konsumen. Seorang produsen akan bisa menetapkan suatu harga barang berdasarkan dari beberapa hal termasuk biaya-biaya yang dikeluarkan dalam memproduksi suatu barang, selain dari jumlah permintaan barang dari konsumen, keuntungan yang ingin diperoleh, juga daya saing yang bisa saja terjadi anatar sesame produsen barang yang sama. Demi kestabilan harga, produsen akan melakukan hal-hal seperti menyediakan potongan harga atau diskon, atau melakukan promosi sehingga permintaan barang dari konsumen akan tetap dia peroleh dan permintaan barang juga bisa meningkat

Fungal biotechnology

Fungi are used in many industrial processes, such as the production of enzymes, vitamins, polysaccharides, polyhydric alcohols, pigments, lipids, and glycolipids. Some of these products are produced commercially while others are potentially valuable in biotechnology. Fungal secondary metabolites are extremely important to our health and nutrition and have tremendous economic impact. In addition to the multiple reaction sequences of fermentations, fungi are extremely useful in carrying out biotransformation processes. These are becoming essential to the fine-chemical industry in the production of single-isomer intermediates. Recombinant DNA technology, which includes yeasts and other fungi as hosts, has markedly increased markets for microbial enzymes. Molecular manipulations have been added to mutational techniques as a means of increasing titers and yields of microbial processes and in the discovery of new drugs. Today, fungal biology is a major participant in global industry. Moreover, the best is yet to come as genomes of additional species are sequenced at some level (cDNA, complete genomes, expressed sequence tags) and gene and protein arrays become available

Catalytic Asymmetric Synthesis of Bicycloprolines by a 1,3-Dipolar Cycloaddition/Intramolecular Alkylation Strategy

This document is the Accepted Manuscript version of a Published Work that appeared in final form inJournal of Organic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.joc.6b01100 to Published Work, see http://pubs.acs.org/page/policy/articlesonrequest/index.htmlThe diastereoselective one-pot synthesis of hexahydrocyclopenta [b] pyrrole derivatives (bicycloprolines) has been achieved by base-mediated reactions of (E)-tert-butyl 6-bromo-2-hexenoate with α-imino esters. The catalytic asymmetric version of this process has been efficiently achieved using the CuI/(R)-DTBM-Segphos complex as a catalyst following a two-step 1,3-dipolar cycloaddition/intramolecular alkylation sequence.Financial support of this work by the Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional (MINECO CTQ2012-35790 and MINECO/FEDER CTQ2015-66954-P) are gratefully acknowledged. M.G.-E. and A.P.-E. thank the MICINN for predoctoral fellowship

Restructuring of supported Pd by green solvents: an operando Quick EXAFS (QEXAFS) study and implications for the derivation of structure-function relationships in Pd catalysis

Transmission electron microscopy (TEM) is commonly used as an ex-situ technique to determine structural changes by comparing images of catalyst particles before and after a reaction. This requires the use of an alcoholic solvent to disperse the particles on a grid. In this work, we will show that Pd catalysts can be transformed during the procedure, by using EXAFS to determine the structure of Pd catalysts in different environments (as dry or wet samples). Supported palladium nanoparticles exposed to aqueous ethanolic solution (50% w/v) are transformed to a common, reduced, and hydrogen-contaminated state, irrespective of their initial habit or support. Catalysts comprised of nanosize PdO are reduced at ca. 350 K, whereas samples comprised of very small (ca. ≤ 10 atoms) Pd particles react with the solvent at just above room temperature and agglomerating with considerable loss of dispersion. As such any potential benefits to catalysis sought through the synthesis of very highly dispersed metallic Pd supported upon a range of inorganic dispersants will be rapidly erased through the action of such solvents

Effects of Cl on the reduction of supported PdO in ethanol/water solvent mixtures

The reduction of γ-Al2O3-supported PdO in flowing aqueous ethanol was investigated. Quick EXAFS (QEXAFS) performed at the Pd K-edge reveals that the presence of Cl can have a profound effect on the reduction process. At low loadings of Pd (1 wt-%), the size dependency of the process is inverted, compared to Cl-free samples. The extent of reduction was found to be dependent on loading/particles size. It is shown, using in situ QEXAFS at the Cl K- and Pd L3-edges, that residual Cl is not removed by the flowing solvent mixture, even at an elevated temperature of 350 K. The origins of these behaviours are discussed in terms of the differing effects that Cl may have when bonded to oxidic or reduced metal centres and the results were compared to earlier observations made on the effects of Cl on commercial polyurea encapsulated Pd ENCAT™ NP 30 catalysts

Synthesis of estrogens in progenitor cells of adult fish brain: Evolutive novelty or exaggeration of a more general mechanism implicating estrogens in neurogenesis?

International audienceIn contrast to other vertebrates, in which the adult brain shows limited adult neurogenesis, teleost fishes exhibit an unparalleled capacity to generate new neurons as adults, suggesting that their brains present a highly permissive environment for the maintenance and proliferation of adult progenitors. Here, we examine the hypothesis that one of the factors permitting establishment of this favourable environment is estradiol. Indeed, recent data showed that radial glial cells strongly expressed one of two aromatase duplicated genes. Aromatase is the estrogen-synthesizing enzyme and this observation is of great interest, given that radial glial cells are progenitor cells capable of generating new neurons. Given the well-documented roles of estrogens on cell fate, and notably on cell proliferation, these data suggest that estradiol could be involved in maintaining and/or activating these progenitors. Examination of recent data in birds and mammals suggests that the situation in fish could well be an exaggeration of a more general mechanism implicating estrogens in neurogenesis. Indeed, there is accumulating evidence that estrogens are involved in embryonic, adult or reparative neurogenesis in other vertebrates, notably in mammals

Blunt traumatic aortic injuries of the ascending aorta and aortic arch: a clinical multicentre study

[Abstract] Objective. To report the clinical and radiological characteristics, management and outcomes of traumatic ascending aorta and aortic arch injuries. Methods. Historic cohort multicentre study including 17 major trauma patients with traumatic aortic injury from January 2000 to January 2011. Results. The most common mechanism of blunt trauma was motor-vehicle crash (47%) followed by motorcycle crash (41%). Patients sustaining traumatic ascending aorta or aortic arch injuries presented a high proportion of myocardial contusion (41%); moderate or greater aortic valve regurgitation (12%); haemopericardium (35%); severe head injuries (65%) and spinal cord injury (23%). The 58.8% of the patients presented a high degree aortic injury (types III and IV). Expected in-hospital mortality was over 50% as defined by mean TRISS 59.7 (SD 38.6) and mean ISS 48.2 (SD 21.6) on admission. Observed in-hospital mortality was 53%. The cause of death was directly related to the ATAI in 45% of cases, head and abdominal injuries being the cause of death in the remaining 55% cases. Long-term survival was 46% at 1 year, 39% at 5 years, and 19% at 10 years. Conclusions. Traumatic aortic injuries of the ascending aorta/arch should be considered in any major thoracic trauma patient presenting cardiac tamponade, aortic valve regurgitation and/or myocardial contusion. These aortic injuries are also associated with a high incidence of neurological injuries, which can be just as lethal as the aortic injury, so treatment priorities should be modulated on an individual basis