306,368 research outputs found
Kinky perceived demand curves and Keynes-Negishi equilibria
No full textThe label “Keynes-Negishi equiibria” is attached here to equilibria in a monetary economy with imperfectly competitive product and labor markets where business firms and labor unions hold demand perceptions with kinks - as posited in Negishi’s 1979 book Microeconomic Foundations of Keynesian Macroeconomics. Such equilibria are defined in a general equilibrium model, and shown to exist. Methodological implications are briefly discussed in a concluding section.Equilibrium, imperfect competition, perceived demands, kinky demand, princing rules, union wage model, union objectives, cash-in-advance
Palladium-catalyzed Negishi coupling and zirconium -catalyzed asymmetric carboalumination of alkenes (ZACA): Powerful tools in the synthesis of natural products
No full textPd-catalyzed Negishi coupling has been serving as one of the powerful methods for the construction of carbon-carbon bond since its first discovery in 1976. Many research groups have utilized Negishi coupling to synthesize various types of natural products or complex organic compounds as the pivotal step. To overcome a long-standing synthetic challenge of preparing ( Z)-trisubstituted alkenes using Pd-catalyzed cross-coupling, it is found that hydroboration of 1-bromo-1-alkynes, migratory insertion, and transmetallative iodinolysis in one-pot to synthesize (Z)-trisubstituted iodides is a highly efficient and stereoselective method, which proved to be excellent for the synthesis of some natural products containing (Z)-trisubstituted alkenes. As depicted in detail in chapter one, was the development of the above methodology and its application to the synthesis of fragments of discodermolide, (-)-callystatin A and archazolid A and B natural products, and most importantly, to the total synthesis of (6E,10Z)- O-Methylmyxalamide D, for the first time. As discussed in chapter two, the 1:1 mixture of DIBAL-H and Cp2 ZrCl2 in THF provides a convenient and genuine equivalent to HZrCp2Cl, which has been employed in hydrozirconation of alkynes-Pd-catalyzed Negishi coupling tandem processes for the synthesis of conjugated dienes, or polyenes. Zr-catalyzed Asymmetric Carboalumniation of Alkenes (ZACA) has emerged as an efficient and useful method for asymmetric synthesis of 2-methyl-1-alkanol, usually of 70–80% ee. Despite the high efficiency and high overall stereoselectivity (≥98% overall ee) for the synthesis of deoxypolypropionate units containing at least two chiral carbon centers, thanks to the chromatography separation of diastereoisomers, ZACA reaction thus far failed to produce those compounds of high stereoselectivity (≥98% ee) that contain only one chiral carbon center or even two chiral ones, which are unable to effectively interact for facile chromatographic separation. But nevertheless, lipase-catalyzed acetylation and ZACA synergy provides a good solution to this problem. Its synthetic power has been eloquently demonstrated through the synthesis of a certain type of natural products, as discussed in Chapter three
Palladium-catalyzed alkynylation
No full textA brief overview of the scope of the four major protocols with respect to the electrophilic cross-coupling partners is presented in somewhat irrespective of relative merit and demerits among these protocols. Thus, some noteworthy recent advances in which more critical comparisons among the four protocols mentioned will made are discussed. In addition, some recent methodological developments with emphasis on searches for superior phosphine and other ligands as well as one mechanistic aspects of the Pd-catalyzed alkynylation are discussed as well
The Negishi-tô and Negishi as a place
No full textThe Negishi-tô, the Negishi Party, was a group of bunjin, people in the pursuit of elegant things, in the Meiji period. The group was composed mostly of authors and painters. The Negishi-tô was not a literary or an artistic association but a sort of social club. Most of the members of the Negishi-tô lived in Negishi, Tokyo, or its neighborhood in about 1887 (Meiji 20). Nobody knows who began to call it the Negishi-tô, but it is certain that the name of the group derived from the name of the place, Negishi.Negishi lies in the northeast of Tokyo, on the far side of the hills of Ueno. In the Edo period it was called Kanasugi-mura, in Toshima-gun, Musashi Province, and was a quiet land at the distance of about six kilometers from the central part of Edo. Most of Negishi was farmland in about the middle of the 18th century. From about the beginning of the 19th century the number of villas owned by wealthy merchants situated between the farms increased, and at the same time bunjin began to live there. 30 bunjin or more lived there in 1835, and it became a place of dissemination of a specific culture.The Ogyô-no-matsu was one of the “famous eighteen pines” of Edo, and it is said that people could see the tree from anywhere in Negishi until 1928. A brook named Otonashi-gawa flowed by the Ogyô-no-matsu. It ran through the center of Negishi from east to west, and rich merchants’ villas, bunjins’ houses, and so on stood in a line along the brook. Negishi was famous as a natural habitat of Japanese bush warblers, too. The Uguisu-e, a competition of Japanese bush warblers singing, was held in the Ume-yashiki at the side of the Otonashi-gawa, and it was crowded with people who came from all over Japan every year in March.The number of houses in Negishi increased after the Meiji period. But in the middle of the Meiji period, which was the active period of the Negishi-tô, Negishi was very much a remainder of the Edo period. I think they chose Negishi as a suitable place for bunjin to live and gather according to their image of what bunjin were. They came to be called not the Shitaya-tô or the Yanaka-tô but the Negishi-tô. This is probably because people generally shared the same image of Negishi in those days
Transition metal catalyzed carbon-carbon bond forming reactions. Stereoselective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation- Palladium catalyzed cross-coupling
No full textThe first chapter gives a general account of the history of organometallic chemistry and the also discusses the importance of d-block transition metals and its usefulness in the development of cross-coupling. The chapter shows the usefulness of Pd-catalyzed cross-coupling in carbon-carbon bond formation and its general scope. The next chapter, alkenyl-alkenyl cross-coupling by Negishi alkenylation lead to the stereoselective synthesis of all possible isomers of dienoic and trienoic esters via Alkyne Elementometalation–Pd catalyzed cross-coupling tandem process in the presence of PEPPSI catalyst. The synthesis of dienes by Negishi coupling was also compared with other methods such as carbonyl olefination (HWE and SG), Heck alkenylation and Suzuki coupling. Pd-catalyzed alkenylation–carbonyl olefination synergistic approach was used in the synthesis of some isomers of trienoic esters. In the last chapter, emphasis is given towards exploring high turnover numbers (TONs) in Pd-catalyzed alkenyl-alkenyl cross-coupling. Negishi coupling between alkenylzirconium species and alkenyl halide lead to the TONs in the range of 105-107. This will help lower the catalyst loading and reduce the cost in large scale industrial applications of Pd-catalyzed cross-coupling reactions
Imperfect competition à la Negishi also with fixed costs
No full textThe paper studies equilibria for economies with imperfect competition and non-convex technologies. Following Negishi firms maximise profits under downward-sloping perceived demand functions. Negishi's assumptions, in particular the assumption of a single monopolistic competitor in each market, are relaxed. Existence of equilibria is obtained, under otherwise standard assumptions, for production sets defined in each firm by the union of a convex technology and a technology subjected to fixed costs. In the light of a counterexample it is assumed that fixed factors are distinct from variable factors. Technically the proof rests on pricing rules.imperfect competition, fixed costs, general equilibrium, perceived demands, pricing rules
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Cross-coupling di Negishi su cloruri cinnamoilici: sintesi del Millepachine
No full textITA: In questo lavoro è stata eseguita la sintesi totale del Millepcahine a partire da composti commercialmente disponibili. L'ultimo step sintetico ha previsto un cross-coupling di Negishi tra il cloruro di parametossicinnamoile e l'8-iodo-5-metossi-2,2-dimetil-2H-cromene, la cui sintesi non era mai stata riportata finora.
Inoltre, sempre attraverso cross-coupling di Negishi acilativi, sono stati preparati altri calconi da cloruri cinnamoilici e ioduri aromatici.
ENG: During this work the total synthesis of Millepcahine was performed starting from commercially available compounds. The last synthetic step involved a Negishi cross-coupling between paramethoxycinnamoyl chloride and 8-iodo-5-methoxy-2,2-dimethyl-2H-chromene, which synthesis had never been reported.
Furthermore, again through acylative Negishi cross-coupling, other chalcones were prepared from cinnamoyl chlorides and aromatic iodides
Catalytic and selective conversion of (Z)-2-en-4-ynoic acids to either 2H-pyran-2-ones in the presence of ZnBr2 or (Z)-5-alkylidenefuran-2(5H)-ones in the presence of Ag2CO3
No full textDispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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