Parallel displaced and sandwich configurations of hexafluorobenzene-substituted benzene dimers are studied by ab initio molecular orbital methods up to the MP2(full)/aug-cc-pVDZ level theory reveal how substituents influence π−π interactions. Two minimum energy found, one with substituent group away from π-face hexafluorobenzene ring (2a−f) other on top (3a−f). Higher binding energies predicted for All (4a−e) found be saddle points potential surfaces. A parallel-displaced configuration is...

Current models describe aromatic rings as polar groups based on the fact that benzene and hexafluorobenzene are known to have large permanent quadrupole moments. This report describes a quantitative study of interactions between oxygen lone pair rings. We found even electron-rich pairs exhibit attractive interactions. Free energies determined using triptycene scaffold equilibrium constants were by low-temperature 1H NMR spectroscopy. An X-ray structure analysis for one model compounds...

Natural polyphenols may play an important role in aluminum detoxification some plants. We examined the interaction between Al(3+) and purified high molecular weight pentagalloyl glucose (940 Da) oenothein B (1568 Da), related compound methyl gallate (184 at pH 4 6. used spectrophotometric titration chemometric modeling to determine stability constants stoichiometries for aluminum-phenol (AlL) complexes. The structures spectral features of aluminum-methyl complexes were evaluated with quantum...

[reaction: see text] Triptycene-derived compounds have been prepared to serve as conformational equilibrium reporters for direct measurements of arene-arene interactions in the parallel-displaced orientation. A series such bearing arenes with different substituents were synthesized, and ratios syn anti conformers determined by variable-temperature NMR spectroscopy. The conformer allows attached interact each other while does not. free energies derived from syn/anti chloroform range slightly...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOn the 1,3-isomerization of nonracemic .alpha.-(alkoxy)allylstannanesJames A. Marshall, Gregory S. Welmaker, and Benjamin W. GungCite this: J. Am. Chem. Soc. 1991, 113, 2, 647–656Publication Date (Print):January 1, 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://pubs.acs.org/doi/10.1021/ja00002a038https://doi.org/10.1021/ja00002a038research-articleACS PublicationsRequest reuse permissionsArticle...

Macrocyclic propargyl acetates containing a furan ring were prepared by using CrCl(2)-promoted reaction. In the presence of either Au(I) or Au(III) catalyst, tandem 3,3-rearrangement/transannular [4+3] cycloaddition reaction occurred to give that are regio- and diastereospecific. The regiochemistry product is controlled position acetoxy group in starting material stereochemistry depends on size.

Attractive interactions between substituted arenes in the parallel displaced configuration have been quantitatively studied using triptycene-derived molecular conformational reporters. Charge-transfer bands are observed for models where strong donor and acceptors. Substituent effects on strength of aromatic interaction follow opposite trends strongly electron-deficient mildly perturbed arenes. The free energy with electron donors acceptors does not a linear correlation Hammett plot....

The stacking interactions between an aromatic ring and a pyridine or pyrimidine are studied by using series of triptycene-derived scaffolds. indicative ratios the syn anti conformers were determined variable-temperature NMR spectroscopy. conformer aligns attached heterocycle in parallel-displaced orientation while sets two rings apart from each other. Comparing to corresponding control compounds where benzene is position heterocycle, higher attractive observed as indicated syn/anti ratios....

Ab initio calculations have been used to investigate the interaction energies of dimers dimethyl ether with benzene, hexafluorobenzene, and several monosubstituted benzenes. The potential energy curves were explored at MP2/aug-cc-pVDZ level for two basic configurations dimers, one in which oxygen atom was pointed towards aromatic ring other away from ring. Once optimum intermolecular distances between had determined each both level, single point performed MP2/aug-cc-pVTZ level. A CCSD(T)...

Interactions between two aromatic rings with various substituents in a near-sandwich configuration have been quantitatively studied by using the triptycene derived molecular models. This model system allows stacking arrangement of arenes to assume near-perfect face-to-face its ground state conformation. Comparing our previous study parallel displaced configuration, repulsive interactions are predominant for most currently studied. However, if one arene is strongly electron deficient (Ar2 =...

[formula: see text] 2-Deoxy-2-iodo- and 2-deoxy-2-bromoglucopyranosyl trichloroacetimidates 8-10 22 are extremely useful precursors of 2-deoxy-beta-glycosides. These reactive glycosyl donors undergo highly stereoselective glycosidation reactions at -78 degrees C with a range acceptors using TBS-OTf as the activating agent. beta-Glycosides obtained > or = 19:1 selectivity in six seven examples reported herein.

The tetraacetylenic compound, (S)-minquartynoic acid (1), is synthesized in seven linear steps and 17% overall yield from commercially available azelaic monomethyl ester. key step a one-pot three-component Cadiot−Chodkiewicz reaction to construct the tetrayne unit without using either diyne or triyne intermediate.

[reaction: see text] Triptycenes with C1-MeO/RCOO (R = H, Me, Et, i-Pr, CF3) and C9-XC6H4CH2 (X F, CN, have been prepared to determine lone pair-arene interactions in the off-center configuration. The ratios of syn anti conformers were determined by low-temperature NMR spectroscopy. conformer allows attached arene MeO/ester interact each other while does not. free energies interaction derived from syn/anti ratios. Compound 7 ester series X H R CF3 is only compound that shows a slightly...

Attractive interactions between a substituted benzene ring and an α-substituted acetate group were determined experimentally by using the triptycene model system. The attractive interaction correlates well with Hammett constants σ(m) (R(2)=0.90), but much better acidity of α-protons (R(2)=0.98).

Gold catalysts with N-heterocyclic carbene ligands have become an attractive tool for organic synthesis. Two new gold complexes (9, 11) are prepared and their structures determined by X-ray structural analysis. Their catalytic activities been studied a intramolecular cyclopropanation reaction starting from the propargyl esters tethered to terminal alkene. Although no or low enantioselectivity was observed 9 11, insight gained this study is importance of steric effects NHC ligand.

Abstract With the use of benzonitrile‐stabilized Au I catalyst [Au(IPr)(NCPh)]SbF 6 ( Ic ; IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene), a spectrum reactivity is observed for propargyl ester 4 with cyclic vinyl ethers, ranging from exclusively [3C+2C] cycloaddition reactions to cyclopropanation depending only on structure substrate. Some initially formed products rearrange into corresponding formally after treatment fresh complex at 80 °C. Vinylcyclopropanes dihydrofuran and...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTCharacterization of a Water-Soluble, Helical β-PeptideBenjamin W. Gung, Dong Zou, Apryll M. Stalcup, and Charles E. CottrellView Author Information Department Chemistry Biochemistry, Miami University, Oxford, Ohio 45056 Chemistry, University Cincinnati, 45221 Campus Chemical Instrument Center, The State Columbus, 43210 Cite this: J. Org. Chem. 1999, 64, 7, 2176–2177Publication Date (Web):March 11, 1999Publication History Received5 June...

Transition-state structures for the allylboration reaction between tartrate ester and tartramide modified allylboronates acetaldehyde are located at B3LYP/6-31G* level of theory. An attractive interaction boron-activated aldehyde or amide carbonyl oxygen lone pair is found to play a major role in favored transition states 11a 13. This appears be electrostatic origin. However, an n → π* charge-transfer type has not been ruled out. The distance (2.77 Å) aldehydic hydrogen state 13 beyond sum...