A Study of Intramolecular Hydrogen Bonding in Levoglucosan Derivatives

Through space JFH spin-spin coupling constant transmission pathways in 2-(trifluoromethyl)thiophenol: formation of unusual stabilizing bifurcated CFHS and CFSH interactions

Given its importance and the possibility of organic F to participate in hydrogen bonds (H-bonds), the understanding of its behavior as a H-bond acceptor with different donors is crucial. The interest in organofluorine compounds and the works related to the study of the participation of this atom in non-covalent interactions is constantly growing. Following recent studies in this subject, we evaluated the existence of two bifurcated intramolecular interactions, a bifurcated CFHS H-bond in the cis conformer of 2-trifluoromethylthiophenol and an unusual, bifurcated CFSH interaction in the trans conformer. The JFH spin-spin coupling constant (SSCC) was evaluated for 2-trifluoromethylthiophenol both experimentally by 1H and 19F NMR and theoretically using the natural bond orbitals (NBO), the quantum theory of atoms in molecules (QTAIM) and the non-covalent interactions (NCI) framework. Although both interactions are crucial for the stabilization of the conformer geometries, the observed positive JFH spin-spin coupling constant (SSCC) is mainly resultant from the trans conformer, which has a large calculated positive SSCC, and is transmitted through steric interactions involving the F lone pairs and the σSH bonding orbital.

Fluorinated carbohydrates as chemical probes for molecular recognition studies. Current status and perspectives

This review provides an extensive summary of the effects of carbohydrate fluorination with regard to changes in physical, chemical and biological properties with respect to regular saccharides. The specific structural, conformational, stability, reactivity and interaction features of fluorinated sugars are described, as well as their applications as probes and in chemical biology.

Cis/Trans Energetics in Epoxide, Thiirane, Aziridine and Phosphirane Containing Cyclopentanols: Effects of Intramolecular OH⋯O, S, N and P Contacts

A recent computational analysis of the stabilizing intramolecular OH⋯O contact in 1,2-dialkyl-2,3-epoxycyclopentanol diastereomers has been extended to thiiriane, aziridine and phosphirane analogues. Density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2) and CCSD(T) coupled-cluster computations with simple methyl and ethyl substituents indicate that electronic energies of the cis isomers are lowered by roughly 3 to 4 kcal mol⁻¹ when the OH group of these cyclopentanol systems forms an intramolecular contact with the O, S, N or P atom on the adjacent carbon. The results also suggest that S and P can participate in these stabilizing intramolecular interactions as effectively as O and N in constrained molecular environments. The stabilizing intramolecular OH⋯O, OH⋯S, OH⋯N and OH⋯P contacts also increase the covalent OH bond length and significantly decrease the OH stretching vibrational frequency in every system with shifts typically on the order of −41 cm⁻¹.

Synthetic strategies for fluorination of carbohydrates

Different synthetic strategies for accomplishing regio- and stereoselective fluorinations of carbohydrate scaffolds are discussed in light of the biological implications arising from such substitutions.

Intramolecular hydrogen bonding in conformationally semi-rigid α-acylmethane derivatives: a theoretical NMR study

Conformational mobility is a core property of organic compounds, and conformational analysis has become a pervasive tool for synthetic design. In this work, we present experimental and computational (employing Density Functional Theory) evidence for unusual intramolecular hydrogen bonding interactions in a series of α-acylmethane derivatives, as well as a discussion of the consequences thereof for their NMR spectroscopic properties.