407 research outputs found
Sc(OTf)<sub>3</sub>-Catalyzed Synthesis of Indoles and SnCl<sub>4</sub>-Mediated Regioselective Hydrochlorination of 5-(Arylamino)pent-3-yn-2-ones
No full textHighly substituted indole derivatives bearing alkyl and aryl moieties can be prepared by Sc(OTf)3-catalyzed Friedel–Crafts alkenylation of 5-(arylamino)pent-3-yn-2-ones. In addition, a method for regioselective hydrochlorination of 5-(arylamino)pent-3-yn-2-ones mediated by SnCl4 in moderate to good yields (up to 84%) has been developed. The resulting exclusive Z-selectivity of the C–Cl bond can be further exploited using cross C–N coupling reactions
Sc(OTf)<sub>3</sub>-Catalyzed Synthesis of Indoles and SnCl<sub>4</sub>-Mediated Regioselective Hydrochlorination of 5-(Arylamino)pent-3-yn-2-ones
No full textHighly substituted indole derivatives bearing alkyl and aryl moieties can be prepared by Sc(OTf)3-catalyzed Friedel–Crafts alkenylation of 5-(arylamino)pent-3-yn-2-ones. In addition, a method for regioselective hydrochlorination of 5-(arylamino)pent-3-yn-2-ones mediated by SnCl4 in moderate to good yields (up to 84%) has been developed. The resulting exclusive Z-selectivity of the C–Cl bond can be further exploited using cross C–N coupling reactions
Sc(OTf)<sub>3</sub>-Catalyzed Synthesis of Indoles and SnCl<sub>4</sub>-Mediated Regioselective Hydrochlorination of 5-(Arylamino)pent-3-yn-2-ones
No full textHighly substituted indole derivatives bearing alkyl and aryl moieties can be prepared by Sc(OTf)3-catalyzed Friedel–Crafts alkenylation of 5-(arylamino)pent-3-yn-2-ones. In addition, a method for regioselective hydrochlorination of 5-(arylamino)pent-3-yn-2-ones mediated by SnCl4 in moderate to good yields (up to 84%) has been developed. The resulting exclusive Z-selectivity of the C–Cl bond can be further exploited using cross C–N coupling reactions
FOURIER TRANSRORM EMISSION SPECTROSCOPY OF THE SYSTEM OF YN.
No full textAuthor Institution: Department of Chemistry, University of Arizona; Department of Chemistry, University of WaterlooThe electronic emission spectrum of YN has been observed in the 2.3-2.6 spectral region using a Fourier transform spectrometer. The bands were excited in a yurium hollow cathode lamp in the presence of a trace of molecular nitrogen. The observed bands, with origins at 3882.7625(4), 4229.0457(3), 4528. 6562(46), 4798.5145(13), 5049.4429(20) and 5281.2129(27), have been assigned as the 0-0, 1-1, 3-3, 4-4 and 5-5 vibrational bands, respectively, of the electronic transition. The principal equilibrium constants for the ground state obtained from this analysis are {\AA} and the corresponding excited state values are and {\AA}. This work represents the first observation of the YN molecule
Injectivity of the Connecting Maps in AH Inductive Limit Systems
No full textAbstractLetAbe the inductive limit of a systemwith, whereXn,iis a finite simplicial complex, andPn,iis a projection inM[n,i](C(Xn,i)). In this paper, we will prove thatAcan be written as another inductive limitwith, whereYn,iis a finite simplicial complex, andQn,iis a projection inM{n,i}(C(Yn,i)), with the extra condition that all the mapsψn,n+1areinjective. (The result is trivial if one allows the spacesYn,ito be arbitrary compact metrizable spaces.) This result is important for the classification of simple AH algebras. The special case that the spacesXn,iare graphs is due to the third author.</jats:p
Integral representation of Markov systems and the existence of adjoined functions for Haar spaces
No full textAbstractLet A be a set of real numbers, and let Yn: = {y0,…, yn} be a C̆ebys̆ev system on A. Assume, moreover, that if inf A or sup A belongs to A, then it is a point of accumulation of A at which all yj are continuous. We find necessary and sufficient conditions for the existence of a function yn + 1 such that also {y0,…, yn, yn + 1} is a C̆ebys̆ev system on A. This theorem generalizes earlier results of Zielke and of the author. The proof is based on an integral representation of Markov systems that slightly extends a previous result of Zielke
Arylchlorocarbenes in the synthesis of heterocycles containing two nitrogen atoms
No full textSubstituted pyrazoles and pyrrolo[1,2-c]pyrimidines were prepared from the reaction of arylchlorocarbenes with 1,2-diazabuta-1,3-dienes and 4-vinylpyrimidines, respectively.PT: J; CR: ATTANASI A, 1998, J ORG CHEM, V63, P9880 ATTANASI OA, 1977, SYNLETT, P1128 ATTANASI OA, 1999, TETRAHEDRON LETT, V40, P3891 BONINI BF, 1981, J CHEM SOC P1, P2322 BONNEAU R, 1999, J PHOTOCH PHOTOBIO A, V126, P31 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 KUEHNE ME, 1964, J ORG CHEM, V29, P1582 LIU MTH, 1994, INT J CHEM KINET, V26, P1179 MAIBORODA DA, 1997, J ORG CHEM, V62, P7100 MINGUEZ JM, 1996, J ORG CHEM, V61, P4655 MOYANO EL, 1998, J ORG CHEM, V63, P8188 OVERBERGER CG, 1954, J AM CHEM SOC, V76, P1879 PERKAMPUS HH, 1972, TETRAHEDRON, V28, P2099 ROMASHIN YN, 1999, CHEM COMMUN 0307, P447 ROMASHIN YN, 1999, TETRAHEDRON LETT, V40, P7163 WONG JL, 1965, J ORG CHEM, V30, P2398; NR: 16; TC: 6; J9: CHEM COMMUN; PG: 2; GA: 324XFSource type: Electronic(1
On a generalization of a conjecture of Grosswald
No full textWe generalize a conjecture of Grosswald, now a theorem due to Filaseta and Trifonov, stating that the Bessel polynomials, denoted by yn(x), have the associated Galois group Sn over the rationals for each n. We consider generalized Bessel polynomials yn,β(x) which contain interesting families of polynomials whose discriminants are nonzero rational squares. We show that the Galois group associated with yn,β(x) always contains An if β≥0 and n sufficiently large. For β<0 the Galois group almost always contains An. It is further shown that for β<−2, under the hypothesis of the abc conjecture, the Galois group of yn,β(x) contains An for all sufficiently large n. Using these results, an earlier work of Filaseta, Finch and Leidy and the first author concerning the discriminants of yn,β(x), we are able to explicitly describe the instances where the Galois group associated with yn,β(x) is An for all sufficiently large n depending on
The Diwedd/End Garden: a garden for the end of things
Get PDFThis paper investigates the fragmented nature of the Diwedd Garden—a guerrilla garden the author has cultivated from waste and fly-tipped materials on a forgotten plot overlooking Swansea Bay, South Wales. Situated on a liminal hillside alleyway, this assemblage-based practice explores how geographers might adopt ‘broken world thinking’ (Jackson 2014: 221) to engage creatively and critically with the production of urban space. By treating discarded fragments as both the residue and the raw material of regeneration, this paper considers how such acts of reclamation can seed new imaginaries of hope. Over a year, the author helped gather and repurpose what Haraway (2016: 57) calls the ‘excrement of the Capitolocene,’ composting it—quite literally—like a ‘mad gardener’. In doing so, this creative contribution reflects on Latour’s (2004: 246) proposition that ‘the critic is not the one who debunks, but the one who assembles,’ suggesting that creative, material engagement offers alternative, embodied ways of knowing and relating within spatial theory.
Mae'r papur hwn yn ymchwilio i natur dameidiog Gardd Diwedd—gardd guerrilla y mae'r awdur wedi'i meithrin o wastraff a deunyddiau sydd wedi cael eu tipio'n anghyfreithlon ar ddarn o dir sydd wedi mynd yn angof ac yn edrych dros Fae Abertawe. Ar lwybr ar ochr bryn, mae'r ymchwil hon sy'n seiliedig ar ddull cydosod yn mynd i’r afael â sut y gallai daearyddwyr fabwysiadu 'broken world thinking' (Jackson 2014: 221) i ymwneud yn greadigol ac yn feirniadol â chreu gofod trefol. Drwy drin darnau a luchiwyd yn weddillion ac yn ddeunydd crai adfywio, mae'r papur hwn yn ystyried sut y gall gweithredoedd adfer o'r fath ddychmygu gobaith ar ei newydd wedd. Dros gyfnod o flwyddyn, roedd yr awdur wedi helpu i gasglu ac ailddefnyddio'r hyn y mae Haraway (2016: 57) yn ei alw’n 'excrement of the Capitolocene,' gan ei gompostio—yn llythrennol—fel 'garddwr gwallgof'. Wrth wneud hynny, mae'r cyfraniad creadigol hwn yn myfyrio ar gynnig Latour (2004: 246) 'the critic is not the one who debunks, but the one who assembles,' gan awgrymu bod ymwneud yn greadigol ac yn faterol yn cynnig ffyrdd diriaethol a gwahanol o wybod a pherthnasu ym maes theori ofodol
Postembryonic development of amplifying neuroblast lineages in the "Drosophila" brain : proliferation, differentiation and projection patterns
Get PDFWe identified a novel mode of neurogenesis in the larval brain of Drosophila that involves the amplification of neuroblast proliferation through intermediate progenitors (IPs). These intermediate neural progenitors are generated by asymmetric division of a subset of the Drosophila brain neuroblasts, which we refer to as dorsomedial neuroblasts (DM neuroblasts). These neuroblasts divide asymmetrically to self-renew, but unlike the other brain neuroblasts do not segregate the cell fate determinant Prospero to the daughter cells. As a result, in contrast to conventional ganglion mother cells (GMC), intermediate progenitors undergo multiple divisions and express molecular markers of self-renewing neuroblasts. The novel IPs described here have remarkable similarities to the IPs that have been identified recently in mammalian brain development.
We analyzed the type and fate of cells generated in the DM lineages. With a combination of neuronal and glial cell markers we show that the DM lineages generate not only neurons but also glial cells. The DM neuroblasts thus represent the first identified multipotent precursor cells in the fly brain during postembryonic development. We also show that the adult-specific neurons of each DM lineage form several spatially separated axonal fascicles some of which project along larval brain commissural structures which are primordia of future adult midline neuropil. By taking advantage of a DM-specific Gal4 reporter line we identify and follow DM-derived neuronal cells into early pupal stages and demonstrate that neurons of the DM lineages make a major contribution to the developing central complex, in that the numerous columnar elements are likely to be DM lineage-derived. These findings suggest that the amplification of proliferation which characterizes DM lineages may be an important requirement for generating the large number of neurons required in highly complex neuropil structures such as the central complex in the Drosophila brain
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