Direct di- and triamination of polyfluoropyridines in anhydrous ammonia

Intermolecular interactions in the crystalline structure of some polyhalogenated Di- And triamino Pyridines: Spectroscopical perspectives

Supramolecular synthon is identified as a unit and provides important structural and energetic information in the study of organic crystals. However, the direct estimation of the supramolecular interaction remains challenging. In the present work six polyhalogenated di- or triamino pyridines were synthesised, their crystalline structure was characterised, and corresponding supramolecular synthons were studied using a combination of quantum mechanical calculations and FT-IR and Raman spectroscopy. Some distinctive features were identified especially for three vibrational normal modes (RNMs) related to the pyridine ring (viz. RNM₁, RNM₃ and RNM₇) in the vibrational spectra (FT-IR and Raman) of the solid samples, which are due to the supramolecular interactions, hydrogen bond (hb) in particular, according to the quantum mechanical calculations. The comparison between the IR and Raman spectra of experimental and simulated results indicates that the adjacent intermolecular hydrogen bonds between two same molecules extensively exist in the solid samples. Moreover, some quantitative correlation was established among the dimerisation energies for hb dimers (hb1 dimers for compounds 1 and 2), the ring structure defined by the distribution of the substituents and quantitative characteristics of the vibrational spectra, for instance, the splitting magnitudes for RNM₃(2) in IR spectra and the peak gap between RNM₁ and RNM₂ in Raman spectra.

Perfluoropyridine: Discovery, Chemistry, and Applications in Polymers and Material Science

Perfluoropyridine (PFPy) is an organofluorine compound that has been employed for a variety of applications, from straightforward chemical synthesis to more advanced functions, such as fluorinated networks and polymers. This can be directly attributed to the highly reactive nature of PFPy, especially towards nucleophilic aromatic substitution (SNAr). The aim of this review is to highlight the discovery and synthesis of PFPy, discuss its reactive nature towards SNAr, and to summarize known reports of the utilization and thermal analysis of PFPy containing fluoropolymers and fluorinated network materials.

How do electron donating substituents affect the electronic structure, molecular topology, vibrational properties and intra- and intermolecular interactions of polyhalogenated pyridines?

Seven polyhalogenated pyridine derivatives bearing an amino or a hydroxyl group, either at the ortho or para position, were studied using a combined experimental and computational approach. The presence of an electron donating substituent strongly impacted on the geometry, electronic structure, electrostatic properties, molecular topology and vibrational characteristics of these compounds compared to the corresponding polyhalogenated pyridines. In particular the attention was focused on changes in wavenumbers, force constants and intensity of the seven in-plane Ring Normal Modes (RNMs). Due to the nature and position of the substituents, intra- and intermolecular interactions also underwent dramatic modifications, as revealed using Natural Bond Orbital (NBO) analysis, Non-Covalent Interaction (NCI) analysis and Atom-In-Molecule (AIM) theory. Raman and FT-IR spectra of these seven compounds were also collected in solid phase and rationalised by the simulated spectra for hydrogen bonding and/or π-π stacking based homodimers. The present study provides a strategy not only for the vibrational characterisation for the individual compounds, but also for shedding light on the ways of molecular packing in the molecular crystals or cocrystals involving these compounds.

Synthesis of multi-substituted 4-aminopyridines via ring-opening and recyclization reactions of 2-iminopyridines

Synthesis of multi-substituted 4-aminopyridines is developed via a regioselective ring-opening reaction of 2-iminopyridines followed by a 6π-azaelectrocyclization and N-to-N 1,3-sulfonyl group migration process.