DYOTROPIC REARRANGEMENT OF DIARYLETHENES

The analysis of the reaction of dyotropic rearrangement of diarylethenes, which limits the fatigue resistant of this class of photochromic compounds, has been carried out.

Elucidating the Selectivity of Dyotropic Rearrangements of β-Lactones: A Computational Survey

Dyotropic rearrangement of β-lactones is a neglected treasure in the family of multi-bond reactions and pericyclic reactions. Despite its appealling synthetic potential, the complicate migration selectivity greatly limits its broadwide...

Reversible Shifting of a Chemical Equilibrium by Light: The Case of Keto-Enol Tautomerism of a β-Ketoester

Manipulating the equilibrium between a ketone and an enol by exposure to light opens up ample opportunities in material chemistry and photopharmacology since it allows one to reversibly control the content of the enol tautomer, which acts as a hydrogen atom donor, with high spatio-temporal and energy resolution. Although tautomerization of β-ketoesters or their analogs was studied in numerous papers, their light-induced reversible tautomerization to give thermally stable enols (photoenolization) is an unexplored area. To shed light on this “blind spot”, we report an unprecedented property of diarylethene <b>2A</b> assembled from fragments of photoactive dithienylethene and a β-ketoester as part of the cyclohexenone bridge. In a pristine state, the tautomeric equilibrium of <b>2</b> is almost completely shifted towards the ketone. Photocyclization of the hexatriene system results in a new equilibrium system containing a significant fraction of the enol tautomer, both in polar and non-polar solvents. Due to the considerable spectral separation (35 nm), the keto-enol tautomerization process could be observed visually. The tendency of <b>2A </b>to undergo light-induced enolization was proved by isolating a related byproduct of photochemical 1,2-dyotropic rearrangement stabilized in the enolic form. Our results provide a novel tool for controlling the keto-enol tautomerism that might find use in the development of novel photocontrollable processes.

Reversible Shifting of a Chemical Equilibrium by Light: The Case of Keto-Enol Tautomerism of a β-Ketoester

Manipulating the equilibrium between a ketone and an enol by exposure to light opens up ample opportunities in material chemistry and photopharmacology since it allows one to reversibly control the content of the enol tautomer, which acts as a hydrogen atom donor, with high spatio-temporal and energy resolution. Although tautomerization of β-ketoesters or their analogs was studied in numerous papers, their light-induced reversible tautomerization to give thermally stable enols (photoenolization) is an unexplored area. To shed light on this “blind spot”, we report an unprecedented property of diarylethene <b>2A</b> assembled from fragments of photoactive dithienylethene and a β-ketoester as part of the cyclohexenone bridge. In a pristine state, the tautomeric equilibrium of <b>2</b> is almost completely shifted towards the ketone. Photocyclization of the hexatriene system results in a new equilibrium system containing a significant fraction of the enol tautomer, both in polar and non-polar solvents. Due to the considerable spectral separation (35 nm), the keto-enol tautomerization process could be observed visually. The tendency of <b>2A </b>to undergo light-induced enolization was proved by isolating a related byproduct of photochemical 1,2-dyotropic rearrangement stabilized in the enolic form. Our results provide a novel tool for controlling the keto-enol tautomerism that might find use in the development of novel photocontrollable processes.