A stereoselective route to polysubstituted tetrahydroquinolines by benzotriazole-promoted condensation of aliphatic aldehydes and aromatic amines

By the promotion of benzotriazole (20 mol %), two molecules of anilines (or other arylamines) and two molecules of phenylacetaldehyde (or o-bromophenylacetaldehyde) condensed to give a series of 1,2,3,4-tetrahydroquinolines in a stereoselective manner. By the catalysis of SmI(2) or SmI(3), the N-(alpha-aminoalkyl)benzotriazoles derived from anilines and (R)-glyceraldehyde acetonide dissociated to the corresponding iminium and enamine species, which underwent asymmetric [4 + 2] cycloadditions to give optically active tetrahydroquinolines.     

Interpolating amplitude equations from an embedding technique

The variable phase approach to potential scattering is regarded as an embedding technique. Algorithms are presented for studying the spatial behaviour of off-shell T matrices.     

Generation of reactive low-valent titanium species using metal--arenes as efficient organic reductants for TiCl(3): applications to organic synthesis

A comprehensive study on the use of metal-arene systems as organic reductants for TiCl(3) has resulted in an efficient method for the generation of highly reactive low-valent titanium (LVT) reagents. The activated titanium species could be prepared by refluxing a mixture of substoichiometric amounts of arenes, TiCl(3), and Li/Mg in THF or DME. Among the LVT reagents screened, TiCl(3)--Li--naphthalene--THF (reagent I) was the best for coupling of carbonyls to olefins. The reagent could carry out the McMurry olefination of both aromatic and aliphatic substrates at a lower temperature and in a much reduced time as compared to the conventional procedures. Subtle changes in the method of preparation of the LVT reagents influenced the stereoisomeric ratio of the olefins. The reagent was also useful for the synthesis of O- and N- heterocycles and vicinal diamines via intramolecular carbonyl coupling and reductive duplication of imines, respectively.     

Inverse problem of the variational calculus for higher KdV equations

It is shown that the usual Hamilton's variational principle supplemented by the methodology of the integer-programming problem can be used to construct expressions for the Lagrangian densities of higher KdV fields. This is demonstrated with special emphasis on the second and third members of the hierarchy. However, the method is general enough for applications to equations of any order. The expressions for Lagrangian densities are used to calculate results for Hamiltonian densities that characterize Zakharov-Faddeev-Gardner equation. Received 27 January 2002 / Received in final form 6 May 2002 Published online 24 September 2002     

Rate coefficients for the OH + HC(O)C(O)H (glyoxal) reaction between 210 and 390 K

Rate coefficients, k1(T), over the temperature range of 210-390 K are reported for the gas-phase reaction OH + HC(O)C(O)H (glyoxal) --> products at pressures between 45 and 300 Torr (He, N2). Rate coefficients were determined under pseudo-first-order conditions in OH using pulsed laser photolysis production of OH radicals coupled with OH detection by laser-induced fluorescence. The rate coefficients obtained were independent of pressure and bath gas. The room-temperature rate coefficient, k1(296 K), was determined to be (9.15 +/- 0.8) x 10-12 cm3 molecule-1 s-1. k1(T) shows a negative temperature dependence with a slight deviation from Arrhenius behavior that is reproduced over the temperature range included in this study by k1(T) = [(6.6 +/- 0.6) x 10-18]T2[exp([820 +/- 30]/T)] cm3 molecule-1 s-1. For atmospheric modeling purposes, a fit to an Arrhenius expression over the temperature range included in this study that is most relevant to the atmosphere, 210-296 K, yields k1(T) = (2.8 +/- 0.7) x 10-12 exp[(340 +/- 50)/T] cm3 molecule-1 s-1 and reproduces the rate coefficient data very well. The quoted uncertainties in k1(T) are at the 95% confidence level (2sigma) and include estimated systematic errors. Comparison of the present results with the single previous determination of k1(296 K) and a discussion of the reaction mechanism and non-Arrhenius temperature dependence are presented.     

Trimodal Control of Ion‐Transport Activity on Cyclo‐oligo‐(1→6)‐β‐D‐glucosamine‐Based Artificial Ion‐Transport Systems

Cyclo‐oligo‐(1→6)‐β‐D ‐glucosamines functionalized with hydrophobic tails are reported as a new class of transmembrane ion‐transport system. These macrocycles with hydrophilic cavities were introduced as an alternative to cyclodextrins, which are supramolecular systems with hydrophobic cavities. The transport activities of these glycoconjugates were manipulated by altering the oligomericity of the macrocycles, as well as the length and number of attached tails. Hydrophobic tails of 3 different sizes were synthesized and coupled with each glucosamine scaffold through the amide linkage to obtain 18 derivatives. The ion‐transport activity increased from di‐ to tetrameric glucosamine macrocycles, but decreased further when flexible pentameric glucosamine was introduced. The ion‐transport activity also increased with increasing length of attached linkers. For a fixed length of linkers, the transport activity decreased when the number of such tails was reduced. All glycoconjugates displayed a uniform anion‐selectivity sequence: Cl^?>Br^?>I^?. From theoretical studies, hydrogen bonding between the macrocycle backbone and the anion bridged through water molecules was observed.     

14C labelling as a reliable technique to screen soybean genotypes (Glycine max (L.) Merr.) for iron deficiency tolerance

Journal of Radioanalytical and Nuclear Chemistry - Fifty diverse soybean genotypes were screened for their ability to tolerate iron deficiency stress in a hydroponics experiment with low iron...     

Symmetries and conservation laws of the damped harmonic oscillator

We work with a formulation of Noether-symmetry analysis which uses the properties of infinitesimal point transformations in the space-time variables to establish the association between symmetries and conservation laws of a dynamical system. Here symmetries are expressed in the form of generators. We have studied the variational or Noether symmetries of the damped harmonic oscillator representing it by an explicitly time-dependent Lagrangian and found that a five-parameter group of transformations leaves the action integral invariant. Amongst the associated conserved quantities only two are found to be functionally independent. These two conserved quantities determine the solution of the problem and correspond to a two-parameter Abelian subgroup.      

Quantal Information Entropies for Atoms

The polynomials occurring in the wave functionsof hydrogenic excited states are found to presentdifficulties for a straightforward analytical approachto the study of associated information entropies. A method is suggested to deal with them. It isthen applied to calculate the information entropy forthe Jacobi polynomial. A model calculation is presentedto examine the effect of screening on the entropy sum. It is seen that the sum does not depend onthe choice of screening.