Search results for "Intermolecular"

Fluorescent chemosensors based on cyclohexane: selective sensing of succinate and malonate versus their longer or shorter homologues

2008

The sensing properties towards aliphatic α,ω-dicarboxylates of five cyclohexane-based ligands are described. The studied ligands have been designed following the binding site-signalling unit approach and they all possess thiourea groups as recognition moieties. Ligands 1 and 3 containing naphthalene units can be used as fluorescent sensors as they form intra- or intermolecular excimers in the presence of appropriate dicarboxylates. Selective sensing of succinate and malonate versus their longer or shorter homologues has been observed.

Unprecedented intermolecular transamidation reaction of N-carbamoylmethyl-N'-tosylguanidines.

2003

[reaction: see text] N-Carbamoylmethyl-N'-tosyl guanidine 2 reacts easily with primary alkylamines to afford substituted carboxamides 3. The reaction proceeds via a five-membered-ring intermediate 5, which could be isolated, and features a rare example of an intermolecular transamidation reaction under mild conditions.

Temperature dependence of the static structure factor of ortho-terphenyl in the supercooled liquid regime close to the glass transition

1993

Abstract Studying the temperature dependence of the static structure factor of ortho-terphenyl from the liquid state down to the glass we find that the main peak of S ( Q ) is split into two maxima which behave quite differently. While the maximum at Q =1.4 A −1 is not much affected by the temperature variation the one at 1.9 A −1 is significantly enhanced. This effect is connected with a change of the short range order, i.e. of the intermolecular distances, but evolves continuously. Thus the dynamic anomalies that have been observed in this system around a characteristic temperature T c ≈290 K are not simply due to a discontinuous change in S ( Q ) but can be attributed to the existence of…

3-(1H-Indol-3-yl)-4-(3,4,5-trimethoxyphenyl)-2,5-dihydro-1H-pyrrole-2,5-dione

2005

The crystal structure of the title compound, C21H18N2O5, was determined in order to study the electrocyclic reactivity of 3,4-di­aryl-1H-pyrrole-2,5-dione derivatives. Intermolecular hydrogen bonds form sheets.

The complexation of tetraphenylborate with organic N-heteroaromatic cations

2001

Complexation studies of eleven N-heteroaromatic cations with tetraphenylborate are reported. Tetraphenylborate forms complexes with five cations and reacts to form Lewis-base boranes with six cations. The complexes and the displacement reaction products were characterised by 1H NMR spectroscopy, elemental analysis and crystallographic methods. In the complexes C–H⋯π or N–H⋯π hydrogen bonds are the principal intermolecular interactions. The stability constants for the complexes are determined by 1H NMR titration in acetonitrile–methanol (1 ∶ 1) solution. Crystal structures of four of the complexes and three of the Lewis-base triphenylborane products are reported.

Recent Advances in the Synthesis of Piperidines: Functionalization of Preexisting Ring Systems

2018

Abstract The present review focuses on strategies for the construction of piperidines which have appeared in the literature since 2003 through mid-2017. In a preceding chapter ( 2017AHC191 ), we summarized synthetic methods involving the construction of the piperidine ring from essentially acyclic starting materials in an intra- or intermolecular manner. The present chapter aims at giving a general overview of decoration or modification of previously generated pyridines or piperidines. The hydrogenation of preformed pyridine or pyridinium rings and introduction of substituents into fully saturated piperidines as well as ring expansion of pyrrolidines to piperidines are the most prevalent me…

Die kristallstruktur von oligo[(2-hydroxy-1,3-phenylen)methylen]en

1984

The crystal structure of three tetranuclear phenolic compounds – 6,6′-bis (2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylenediphenol (1), 6-(2-hydroxy-3,5-dimethylbenzyl)-6′-(2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylendiphenol (2), and 6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-6′-(2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylene-diphenol (3) –, was determined by single crystal X-ray analysis. Intramolecular hydrogen bonds between all hydroxyl groups of adjacent phenolic units are found for all molecules. They are directed to the opposite end of the molecule by the ortho-methyl or ortho-tert-butyl group in compounds 2 and 3, while no special orientation is found in 1. Th…

4-Bromophenyl 2,3,4,5,6-pentabromophenyl ether

2002

The title compound, C12H4Br6O, belongs to a group of flame retardants known as polybrominated di­phenyl ethers (PBDE). Intermolecular Br⋯Br contacts in the bc plane give a sheet-like character to the structure of the title compound.

1981

The proton spin-lattice relaxation time T1 was determined at 13,8, 55,2, and 90 MHz in polystyrene (PS-d0) and polystyrene deuterated at the chain (PS-d3) and the phenyl groups (PS-d5), respectively, at temperatures between −130 and +230°C. Furthermore, T1 was measured in isotopic mixtures of PS-d3 and fully deuterated PS-d8 where a separation into intramolecular and intermolecular contributions was possible through the deuteron dilution technique. Above 130°C, various distributions of correlation times provide a semiquantitative understanding of the different motins seen by the protons of the partially deuterated systems. Rotating frame relaxation times in PS-d3 and PS-d5 reveal librationa…

E-Ring extended estrone derivatives: introduction of 2-phenylcyclopentenone to the estrone D-ring via an intermolecular Pauson–Khand reaction

2006

Abstract An expedient synthetic route to E-ring extended estrone derivatives is reported. Estrone-derived cyclopentenones were accessed by an intermolecular Pauson–Khand (PK) cycloaddition. It was found that electron donating and withdrawing substituents in the arylalkyne increased and decreased the yields of PK products, respectively. The stereochemistry of the products was elucidated by X-ray and NMR studies.