Results 321 to 330 of about 383,519 (362)

Studies on the SmI2-promoted pinacol-type cyclization: synthesis of the hexahydroazepine ring of balanol

Journal of Organic Chemistry, 2000
The efficiency of the samarium(II) iodide induced pinacol-type coupling for the construction of seven-membered cyclic amino alcohols has been investigated.
D. Riber, R. Hazell, T. Skrydstrup
semanticscholar   +1 more source

An alternative method for pucker determination in carbohydrates from residual dipolar couplings: a solution NMR study of the fructofuranosyl ring of sucrose.

Journal of the American Chemical Society, 2002
A simple solution NMR method is presented for pucker determination of five-membered rings using only residual dipolar couplings obtained in a single liquid crystalline medium, DMPC/DHPC bicelles (DMPC = dimyristoylphosphatidylcholine; DHPC ...
D. Freedberg
semanticscholar   +1 more source

SHUFFLE-RING: A NEW CONSTANT-DEGREE NETWORK

International Journal of Foundations of Computer Science, 1998
The hypercube as a parallel interconnection network has been of academic and engineering concern for tens of year due to its many merits. However, its increasing node degree is an obvious weakness. Some networks such as the cube-connected cycles (CCC) and the de Bruijn network have been proposed to overcome the increasing degree of the hypercube.
Francis C. M. Lau, Guihai Chen
openaire   +2 more sources

Determination of proton affinities and acidity constants of sugars.

Journal of Physical Chemistry A, 2013
Proton transfer reactions play a key role in the conversion of biomass derived sugars to chemicals. In this study, we employ high level ab initio theoretical methods, in tandem with solvation effects to calculate the proton affinities (PA) and acidity ...
Shuting Feng, C. Bagia, Giannis Mpourmpakis   +2 more
semanticscholar   +1 more source

Ring-Polymer Molecular Dynamics Rate Coefficient Calculations for Insertion Reactions: X + H2 → HX + H (X = N, O).

Journal of Physical Chemistry Letters, 2014
The thermal rate constants of two prototypical insertion-type reactions, namely, N/O + H2 → NH/OH + H, are investigated with ring polymer molecular dynamics (RPMD) on full-dimensional potential energy surfaces using recently developed RPMDrate code.
Yongle Li, Y. V. Suleimanov, Hua Guo
semanticscholar   +1 more source

Scaling approach for intramolecular magnetic coupling constants of organic diradicals.

Journal of Physical Chemistry A, 2013
The intramolecular magnetic coupling constants (J) of 9 diradicals (i-ix) coupled with an aromatic ring were investigated by means of unrestricted density functional theory (DFT) calculations [UB3LYP/6-311++G(d,p)].
K. C. Ko, Daeheum Cho, J. Lee
semanticscholar   +1 more source

Graded Rings of Theta Constants

1972
Let z → θm(τ, z) denote the familiar theta function on Cg;; we recall that m = (m′m″) is in R2g and τ in 𝔖g. If m is in Q2g, we call θm(τ, 0) a theta constant. Since in this chapter we shall mainly consider theta constants rather than theta functions, we make an agreement that θm means the function τ → θm(τ, 0) on 𝔖g; accordingly, we shall write θm(τ ...
openaire   +2 more sources

Synthesis and photophysical properties of difluoroboron complexes of curcuminoid derivatives bearing different terminal aromatic units and a meso-aryl ring.

Journal of Organic Chemistry, 2013
The synthesis of nine curcuminoids and their difluoroboron complexes is described, with seven of them containing a meso-phenyl ring. Dynamic (19)F NMR confirmed the fact that rotation of that meso-aryl fragment is restricted in the latter systems at room
Abdellah Felouat, A. D'Aléo, F. Fages
semanticscholar   +1 more source

Locally nilpotent derivations and their rings of constants. [PDF]

, 2001
Given a UFD R containing Q , we study R-elementary derivations of B = R[Y1,..., Ym], i.e., R-derivations satisfying D( Yi) ∈ R for all i; in the particular case of m = 3, we will show that if R is a polynomial ring in n variables over a field k (of characteristic zero), and a1, a3, a3 ∈ R are three monomials, then the kernel of the derivation i=13ai6 ...
openaire   +2 more sources

A Note on Constants of Integral Derivations in Semiprime Rings

Communications in Algebra, 2013
Let R be a semiprime ring with extended centroid C and with Q its Martindale symmetric ring of quotients. Suppose that δ: R → R is a C-integral derivation. For a subring A of Q, let A(δ) denote the subring of constants of δ in A. We prove that R(δ) and Q(δ) satisfy the same polynomial identities with coefficients in C. In particular, R(δ) is not nil of
Tsiu-Kwen Lee, Yen-Jen Chen
openaire   +2 more sources