Notes

For this behavior, the term "lone pair aromaticity" is proposed
Synthetic access to poly-substituted 6-alkoxyindoles from 1,3-cyclohexanediones and nitroolefins through facile aromatization reaction.Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, 6-Alkoxy-3-arylindoles were efficiently prepared from 1,3-cyclohexanedione enol ethers and beta-nitrostyrenes. Michael addition using the kinetically generated enolate, followed by Zn reduction of a nitro group of the resulting adducts produced the nitrones which were then treated with acetic anhydride to induce aromatization by dehydration and N-acetylation, which furnished the desired indoles by the DDQ oxidation. This methodology provides an easy entry toward various poly-substituted 6-alkoxyindoles.Strategy for Enhancement of (13)C-Photo-CIDNP NMR Spectra by Exploiting Fractional (13)C-Labeling of Tryptophan.Albertstr.

21, 79104 Freiburg, Germany.The photo-CIDNP effect has proven to be useful to strongly enhance NMR signals of photochemically active proteins simply by irradiation with light. The evolving characteristic patterns of enhanced absorptive and emissive NMR lines can be exploited to elucidate the photochemistry and photophysics of light-driven protein reactions. In particular, by the assignment of (13)C NMR resonances, redox-active amino acids may be identified and thereby electron-transfer pathways unraveled, in favorable cases, even with (13)C at natural abundance. If signal enhancement is weak, uniform (13)C isotope labeling is traditionally applied to increase the signal strength of protein (13)C NMR. However, this typically leads to cross relaxation, which transfers light-induced nuclear-spin polarization to adjacent (13)C nuclei, thereby preventing an unambiguous analysis of the photo-CIDNP effect. In this contribution, two isotope labeling strategies are presented; one leads to specific but ubiquitous (13)C labeling in tryptophan, and the other is based on fractional isotope labeling affording sets of isotopologs with low probability of next-neighbor isotope accumulation within individual tryptophan molecules.

Consequently, cross relaxation is largely avoided while the signal enhancement by (13)C enrichment is preserved. This results in significantly simplified polarization patterns that are easier to analyze with respect to the generation of light-generated Captodative Substitution Enhances the Diradical Character of Compounds, Reduces Aromaticity, and Controls Single-Molecule Conductivity Patterns: A Valence Bond Computational Quantum Chemistry , The Hebrew University , Jerusalem 91904 , The present contribution uses a valence bond (VB) perspective to consider the captodative substitution strategy, a method to enhance the diradical character of (potentially aromatic) compounds. We confirm the qualitative reasoning that has generally been used to rationalize the diradical-character-enhancing effect of captodative substitution: this type of substitution scheme disproportionally stabilizes specific Dewar/diradical(oid) VB structures, thus increasing their weight in the full ground-state wave function. Furthermore, we assess the effect of captodative substitution on the aromaticity of the considered compound. We observe a clear trade-off between diradical character and aromaticity for our model systems: as one of these properties increases, the other decreases. This finding is especially significant within the field of single-molecule electronics because it enables unification of the previously observed inverse proportionality between the aromaticity of a compound and the magnitude of conductance through that molecule, with the observed proportionality between diradical character and the magnitude of conductance associated with a compound. To some extent, both properties, i.

e., aromaticity and diradical character, appear to be the flip-sides of the same coin.Triplet State Aromaticity: NICS Criterion, Hyperconjugation, and Charge Effects.Provincial Key Laboratory of Theoretical and Computational Chemistry and, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen Provincial Key Laboratory of Theoretical and Computational Chemistry and, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen Aromaticity, one of the most important concepts in organic chemistry, has attracted considerable interest from both experimentalists and theoreticians. It remains unclear which NICS index is best to evaluate the triplet-state aromaticity. Here, Synthesis of 6-butyl-n-hydroxynaphthimide trifluoromethanesulfonic acid and its Variants carry out thorough density functional theory (DFT) calculations to examine this issue. Our results indicate that among the various state.

The correlations can be improved from 040 to 038 when only neutral species are considered, demonstrating the significant effect of the charge on the triplet-state aromaticity. In Seebio Photochemical Acid-forming Compound , calculations suggest that five-membered cyclic species with "hyperconjugative" aromaticity (and antiaromaticity) in the S0 state will become antiaromatic (and aromatic) in the T1 state, indicating an important role of hyperconjugation. Finally, a moderate © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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