Mechanism of fixation of CO2 with an epoxide catalyzed by ZnBr2 and a choline chloride co-catalyst: a DFT study

The cycloaddition mechanism of the reaction of propylene oxide with CO₂ catalyzed by ZnBr₂/choline chloride is elucidated using a DFT method.

Synthesis of functionalized polycyclic aromatic compounds via a formal [2 + 2]-cycloaddition

A base-promoted formal [2 + 2]-cycloaddition of 2-acyl-2'-vinyl-1,1'-biaryls was developed to provide polycyclic cyclobutanols as a step toward the synthesis of substituted polycyclic aromatic hydrocarbons and their heterocyclic analogues.

Synthesis, photochemistry, and photophysics of butadiene derivatives: influence of the methyl group on the molecular structure and photoinduced behavior

Novel butadiene derivatives display diverse photochemistry and photophysics. Excitation of 2-methyl-1-(o-vinylphenyl)-4-phenylbutadiene leads to the dihydronaphthalene derivative, whereas photolysis of the corresponding model o-methyl analogue results in the formation of the naphthalene-like derivative, deviating from the nonmethylated analogue of the prior starting compound and producing benzobi- and -tricyclic compounds. The effect of the methyl substituents is even more dramatic in the case of the dibutadienes. The parent unsubstituted compound undergoes photoinduced intramolecular cycloaddition giving benzobicyclo[3.2.1]octadiene, whereas the photochemical reaction of the corresponding dimethylated derivative shows only geometrical isomerization due to the steric effect of the substituents. Methyl groups on the butadiene backbones reduce the extent of conjugation, causing a blue-shift of the characteristic absorption band. The fluorescence efficiency is dramatically decreased, as a consequence of nonplanarity and reduced rigidity of the molecules due to the crowding by the methyl and phenyl groups together. Four molecules of very similar structures show dramatically different photoinduced behavior, revealing how changes of the nature and position of the substituents are valuable in understanding the photophysics and photochemistry of these types of compounds.