Results 251 to 260 of about 40,430,947 (286)
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Alkenes in [2+2+2] Cycloadditions
Chemistry – A European Journal, 2016AbstractParticipation of alkenes and allenes in [2+2+2] cycloaddition reactions has attracted much attention recently. This version of the well‐established alkyne cyclotrimerization renders interesting products, such as cyclohexadienes and other polycycles, through cascade processes.
Gema Domínguez +1 more
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Organometallics, 2009
A novel metal-catalyzed, all-alkene [2+2+2] cycloaddition reaction involving a strained and conformationally restricted bis-ene and a diene is reported. Modification of the catalyst leads to competition with a diene-ene [2+2] reaction, and when an alkyne was used in place of the diene, [2+2+2] and [2+2+2+2] cycloaddition reactions occurred involving ...
Paul A. Wender +2 more
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A novel metal-catalyzed, all-alkene [2+2+2] cycloaddition reaction involving a strained and conformationally restricted bis-ene and a diene is reported. Modification of the catalyst leads to competition with a diene-ene [2+2] reaction, and when an alkyne was used in place of the diene, [2+2+2] and [2+2+2+2] cycloaddition reactions occurred involving ...
Paul A. Wender +2 more
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On the classification of nonsingular 2×2×2×2 hypercubes
Designs, Codes and Cryptography, 2012As a first step in the classification of nonsingular 2×2×2×2 hypercubes up to equivalence, we resolve the case where the base field is finite and the hypercubes can be written as a product of two 2×2×2 hypercubes. (Nonsingular hypercubes were introduced by D. Knuth in the context of semifields. Where semifields are related to hypercubes of dimension 3,
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1994
Die thermische [2+2]Cycloaddition von Alkenen 1 ist nach den Woodward-Hoffmann-Regeln 1) suprafacial symmetrieverboten und kann nur in speziellen Fallen erfolgreich durchgefuhrt werden. Hingegen ist das photochemische Pendant erlaubt und wird als praparativ wertvolle Methode zur Bildung von Vierringsystemen 2 vielfaltig genutzt.2–4)
Thomas Laue, Andreas Plagens
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Die thermische [2+2]Cycloaddition von Alkenen 1 ist nach den Woodward-Hoffmann-Regeln 1) suprafacial symmetrieverboten und kann nur in speziellen Fallen erfolgreich durchgefuhrt werden. Hingegen ist das photochemische Pendant erlaubt und wird als praparativ wertvolle Methode zur Bildung von Vierringsystemen 2 vielfaltig genutzt.2–4)
Thomas Laue, Andreas Plagens
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On the 2√2 a × 2√2 a supestructure phase
Proceedings, annual meeting, Electron Microscopy Society of America, 1990Recently Reyes-Gasga et. al. have studied the superstructures phases produced by the ordering of vacancies (or oxygen) in the YBa2Cu3Ox, supercondutor compound. In these papers they also discussed briefly a posible interpretation of the diffraction pattern based on a square unit cell with edges 2√2 a × 2√2 a, where a=0.38nm (fig.
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[2+2], [3+2] and [2+2+2] Cycloaddition Reactions of Indole Derivatives
2010A review with 102 references on [2+2], [3+2] and [2+2+2] cycloaddition reactions involving the indole nucleus.
Fariborz Firooznia +2 more
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An MCSCF study of the X 2 B 2, 2 A 2 and 2 2 B 2 states of benzyl
Journal of the Chemical Society, Faraday Transactions 2, 1987A large basis set (double-zeta + polarisation and diffuse s, p on carbons) calculation is reported on the three electronic states of benzyl, X2B2, 2A2 and 2 2B2, which are of interest experimentally. Because these states cannot be represented by SCF wavefunctions, CASSCF π-space calculations are performed. Geometries are optimised. It is found that the
Julia E. Rice +2 more
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Organic Letters, 2011
The enantioselective N-heterocyclic carbene-catalyzed formal [2 + 2] and [2 + 2 + 2] cycloaddition of ketenes and isothiocyanates were developed. Reaction with N-aryl isothiocyanates at room temperature favors the [2 + 2] cycloaddition, while reaction with N-benzoyl isothiocyanates at -40 °C favors the [2 + 2 + 2] cycloaddition.
Xiao-Na, Wang, Li-Tao, Shen, Song, Ye
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The enantioselective N-heterocyclic carbene-catalyzed formal [2 + 2] and [2 + 2 + 2] cycloaddition of ketenes and isothiocyanates were developed. Reaction with N-aryl isothiocyanates at room temperature favors the [2 + 2] cycloaddition, while reaction with N-benzoyl isothiocyanates at -40 °C favors the [2 + 2 + 2] cycloaddition.
Xiao-Na, Wang, Li-Tao, Shen, Song, Ye
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Solid‐Supported [2+2+2] Cyclotrimerizations
Chemistry – A European Journal, 2006AbstractThe transition‐metal‐catalyzed [2+2+2] cyclotrimerization of a diyne and an alkyne provides a convergent route to highly‐substituted aromatic rings. This reaction possesses distinct drawbacks, especially low chemo‐ and regioselectivities, which hamper its application in combinatorial synthesis. These problems have been solved by the development
Douglas D, Young +2 more
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The Structure of $$2$$ 2 -Pyramidal $$2$$ 2 -Factorizations
Graphs and Combinatorics, 2014A 2-factorization of a simple graph $$\Gamma $$ Γ is called $$2$$ 2 -pyramidal if it admits an automorphism group $$G$$ G fixing two vertices and acting sharply transitively on the others. Here we show that such a $$2$$ 2 -factorization may exist only if $$\Gamma $$ Γ is a cocktail party graph, i.e., $$\Gamma = K_{2n}-I$$ Γ = K 2 n - I with $$I$$ I ...
Marco Buratti, Tommaso Traetta
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