Electrocyclic reactions stereoselectivity of fluorinated olefins derivatives

Wydział Chemii: Zakład Syntezy i Struktury Związków OrganicznychCelem pracy było zbadanie procesów elektrocyklicznych (przede wszystkim w aspekcie ich stereoselektywności i możliwości stereokontroli) wykorzystując oprócz danych eksperymentalnych obliczenia kwantowo-mechaniczne metodami DFT. Rozważając zarówno regułę zachowania symetrii orbitali Woodwarda-Hoffmanna jak i efekt skrętoselektywności, jesteśmy w stanie kontrolować stereoselektywność procesu elektrocyklizacji, który zachodzić może w sposób stereospecyficzny, a układ taki może posłużyć w przyszłości np. jako układ modelowy przy projektowaniu nanorotorów. Opisano układy 4π-elektronowe (fluorowane pochodne 1,3-dimetylo-5-propenylouracylu) oraz 6π-elektronowe (9,10-bis(pentafluoropropenylo)fenantren) ulegające elektrocyklizacji, w których wpływ na skrętoselektywność mają podstawniki „fluorowe” (zarówno elektronodonorowe np. -F jak i elektronoakceptorowe np. -CF3). Efekt skrętoselektywności jest wówczas bardzo wyraźny i może w sposób znaczący wpłynąć na stereoselektywność reakcji elektrocyklizacji. Wyjaśniono obserwowaną stereoselektywność w badanych reakcjach izomeryzacji elektrocyklicznej, wskazując na jej zależność zarówno od skrętoselektywności jak i od: równowagi konformacyjnej substratów, ich parametrów geometrycznych (symetrii), różnic w siłach oscylatorów oraz od możliwości konkurencyjnej, równoległej izomeryzacji rodnikowej.The photochemical properties of fluorinated derivatives of 1,3-dimethyl-5-propenyl uracils (4π-electrons system) were studied assuming that the electrocyclization of the diene would be a dominant reaction. Keeping in mind the Woodward–Hoffmann and torquoselectivity rules, this photoisomerization is the stereospecific reaction. This is a cycle of a sequent reactions capable to provide the selective 360º clockwork rotation, which can be used as a model to design a light-fueled nanomotor.The electocyclization of 6π-electrons systems has been investigated using 9,10-bis(pentafluoropropenyl)phenanthrene as a molecular model of fluorinated derivatives of olefins. The electronic donating/accepting properties of substituents (-F, -CF3) at the terminal position of a triene or cyclohexadiene could determine mode of motion and a stereospecificity of this reaction, where using the concept of torquoselectivity one could predict preferences of such transformation. The reaction mechanisms rationalizing the observed product yields have been proposed on the basis of the DFT calculations. It has been shown that the stereoselectivity and torquoselectivity may stem from the equilibration processes between various conformers having different symmetry and oscillator strengths. Observed photostationary states have been explained taking into consideration the torquoselectivity effect as well as the role of competitive radical mechanism

Polymers and macromolecules containing pentafluorosulfanyl, -SF5 substituent : synthesis, structure, properties and application

The pentafluorosulfanyl (-SF5) moiety is a lesser known and underutilized functional group that displays high electronegativity, chemical and thermal stability, and low surface energy, among other useful properties. As a substituent it is known for almost 60 years, however practical application of the unique -SF5 group in various areas of chemistry has only recently picked up, mostly due to longstanding challenges associated with its synthetic accessibility. Most of the latest attention involving the use of -SF5 has been in medicinal chemistry, but it has also started to feature much more frequently in functional materials design, especially in the area of optoelectronic materials. This review will describe polymers and macromolecules containing -SF5 substituent which has been introduced mainly at the monomer stage

Naphthalene vs. Benzene as a Transmitting Moiety: Towards the More Sensitive Trifluoromethylated Molecular Probes for the Substituent Effects

The application of DFT computational method (B3LYP/6-311++G(d,p)) to mono- and poly(CF3)substituted naphthalene derivatives helps to study changes in the electronic properties of these compounds under the influence of 11 substituents (-Br, -CF3, -CH3, -CHO, -Cl, -CN, -F, -NH2, -NMe2, -NO2, and -OH) to confront substituent effects in naphthalene with an analogous situation in benzene. This paper shows the dependencies of theoretically calculated SESE (Substituent Effect Stabilization Energy) values on empirically determined, well-defined Hammett-type constants (σp, σm, R, and F). Described poly(CF3)substituted derivatives of naphthalene are, so far, the most sensitive molecular probes for the substituent effects in the aromatic system. The presence of the trifluoromethyl groups of such an expressive nature significantly increases the sensitivity of the SESE to changes caused by another substitution. Further, the more -CF3 groups are attached to the naphthalene ring, the more sensitive the probe is. Certain groups of probes show additivity of sensitivity: the obtained sensitivity relates to the sum of the sensitivities of the mono(CF3)substituted probes

Inductive or Field Substituent Effect? Quantum Chemical Modeling of Interactions in 1‑Monosubstituted Bicyclooctane Derivatives

Inductive substituent constants were obtained for systems lacking the resonance effect. The application of the charge of the substituent active region concept to study the substituent effect in 1-X-substituted bicyclooctane derivatives (B3LYP/6-311++G** calculations, X = NMe₂, NH₂, OH, OMe, CH₃, H, F, Cl, CF₃, CN, CHO, COMe, CONH₂, COOH, NO₂, NO) has revealed inductive interactions, which are through bonds

Dependence of the Substituent Effect on Solvent Properties

The influence of a solvent on the substituent effect (SE) in 1,4-disubstituted derivatives of benzene (BEN), cyclohexa-1,3-diene (CHD), and bicyclo[2.2.2]­octane (BCO) is studied by the use of polarizable continuum model method. In all X–R–Y systems for the functional group Y (NO₂, COOH, OH, and NH₂), the following substituents X have been chosen: NO₂, CHO, H, OH, and NH₂. The substituent effect is characterized by the charge of the substituent active region (cSAR­(X)), substituent effect stabilization energy (SESE), and substituent constants σ or <i>F</i> descriptors, the functional groups by cSAR­(Y), whereas π-electron delocalization of transmitting moieties (BEN and CHD) is characterized by a geometry-based index, harmonic oscillator model of aromaticity. All computations were carried out by means of B3LYP/6-311++G­(d,p) method. An application of quantum chemistry SE models (cSAR and SESE) allows to compare the SE in water solutions and in the gas phase. Results of performed analyses indicate an enhancement of the SE by water. The obtained Hammett-type relationships document different nature of interactions between Y and X in aromatic and olefinic systems (a coexistence of resonance and inductive effects) than in saturated ones (only the inductive effect). An increase of electric permittivity clearly enhances communications between X and Y for BEN and CHD systems