Visible light-induced diastereoselective E/Z-photoisomerization equilibrium of the C=C benzofuran-3-one-hydantoin dyad
authors Talhi, O; Lopes, GR; Santos, SM; Pinto, DCGA; Silva, AMS
nationality International
author keywords benzofuran-3-one-hydantoin dyad; E/Z-isomerization; kinetics; photochemistry; TDDFT
abstract The diastereoselective photodependent isomerization equilibrium of E/Z-1,3-ditolyl-5-[3-oxobenzofuran-2(3H)-ylidene] imidazolidine-2,4-dione (5) is reported. Both diastereomers E-5 and Z-5 are stereochemically stable in solid state but show significant photosensibility in solutions of halogenated solvent. The photoisomerization equilibrium of E/Z-5 is therefore deduced from the H-1 NMR profile after visible-light irradiation of both E-5 and Z-5 samples. The results of the kinetic study, monitored by UV-HPLC, reveal that the E/Z equilibrium is diastereoselective and photodependent, being the transformation E -> Z proceeding faster than that of Z -> E, and the E/Z ratio at the equilibrium depends on the used solvent, light source, and temperature. Both diastereomers are visible-light photosensitive tending to coexist together in equilibrium solutions at a determined ratio, which is always in favor of the Z-product assuming a minimum thermodynamic energy and an increased entropy of the system. Time-dependent density functional theory calculations suggest that the photoisomerization mechanism proceeds via a conical intersection involving the first-excited state: Upon irradiation, the E-5 isomer is excited to the S1 potential energy surface, where it relaxes through rotation of the C=C bond and reaches a conical intersection with the ground-state potential energy surface, thus yielding the Z-5 isomer. Copyright (C) 2014 John Wiley & Sons, Ltd.
issn 0894-3230
year published 2014
volume 27
issue 9
beginning page 756
ending page 763
digital object identifier (doi) 10.1002/poc.3335
web of science category Chemistry, Organic; Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000341021800006
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