0000000000124248
AUTHOR
Rosa Tormos
showing 7 related works from this author
Entropy-controlled diastereoselectivity in the photocyclization of rigid derivatives of o-allylaniline.
2002
Two rigid derivatives of o-allylaniline, namely 8-allyl-2-phenyl-1,2,3,4-tetrahydroquinoline (1b) and 7-(trans-2-cinnamyl)-2-methylindoline (1c), have been chosen as suitable systems to study the potential stereoselectivity of the photocyclization process. Photolysis of 1b leads to a mixture of diastereomeric lilolidines 4 (trans/cis), while 1cproduces a mixture of 4 (trans/cis) and the tetrahydropyrrolo[3,2,1-hi]indole derivatives 5 (trans/cis). To disclose whether the diastereoselectivity could be entropy dependent, photolysis of 1b and 1c has been performed at several temperatures. In both cases, linear relationships have been observed when ln(k(t)/k(c)) (the relative reaction rate const…
ChemInform Abstract: Photochemistry of 7-Acetoxybenzopyran Derivatives. Synthesis of Eupatoriochromene and Encecalin.
1990
Abstract The photolysis of the 7-acetoxybenzopyran derivatives 1a-5a has been carried out. Chromene 1a was found to undergo extensive photopolymerization. Chromanone 2a underwent a rather inefficient photo-Fries rearrangement to the 6 - and 8 - acetyl derivatives 2b and 2c . Diacetoxychromene 3a gave the unsaturated ketone 8 as the main product, besides its deacetylation analogue 9 and chromanone 11 . Diacetoxychroman 4a afforded a mixture of four C-acetyl products: 1b, 1c, 2b and 2c , together with Chromene 1a and chromanone 2a. Finally, irradiation of chroman 5a gave rise to a mixture of the two possible photo-Fries products 5b (43%) and 5c (52%). The mechanistic implications of the above…
Xanthone-photosensitized detoxification of the veterinary anthelmintic fenbendazole
2013
Fenbendazole (1) is a common veterinary anthelmintic, toxic to water living microorganisms. Fluorescence quantum yields of 1 were found to be 0.11 in acetonitrile, 0.068 in methanol, 0.034 in cyclohexane, and 0.013 in water. The singlet excited state energy was ca. 96 kcal mol(-1) in all solvents. The phosphorescence spectrum of 1 in ethanol at 77 K displayed a maximum at 450 nm, leading to a triplet energy of 75 kcal mol(-1). Experimental excited state energies agree well with the results of OFT calculations at the time-dependent B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level. Laser flash photolysis (LFP) of 1 at 266 nm led to transients absorbing in the 300-700 nm range, ascribed to radical cat…
Photocyclization of a bichromophoric phenol/olefi system substituted at the methylene spacer - Zwitterions versus H-bridged intermediates in the exci…
2002
Photolysis of (E)- and (Z)-2-(1-ethyl-3-phenylpropenyl)phenol (1 and 2) under a variety of conditions produces a mixture of dihydrobenzopyrans 3 and 4, dihydrobenzofuran 5, cyclopropanes 6 and 7, and rearranged olefin 8. Acidic treatment of 1 and 2 gives a mixture of the six-membered ring products 3 and 4. Remarkable differences, associated with the nature of the precursor and the reaction conditions, are observed in the regiochemistry of cyclization and in the stereochemistry of the dihydrobenzopyrans (3/4 ratio). This points in favour of an H-bridged intermediate, rather than a fully zwitterionic species, as the direct precursor of the photocyclized products.
Photochemistry of 7-acetoxybenzopyran derivatives. Synthesis of eupatoriochromene and encecalin
1989
Abstract The photolysis of the 7-acetoxybenzopyran derivatives 1a-5a has been carried out. Chromene 1a was found to undergo extensive photopolymerization. Chromanone 2a underwent a rather inefficient photo-Fries rearrangement to the 6 - and 8 - acetyl derivatives 2b and 2c . Diacetoxychromene 3a gave the unsaturated ketone 8 as the main product, besides its deacetylation analogue 9 and chromanone 11 . Diacetoxychroman 4a afforded a mixture of four C-acetyl products: 1b, 1c, 2b and 2c , together with Chromene 1a and chromanone 2a. Finally, irradiation of chroman 5a gave rise to a mixture of the two possible photo-Fries products 5b (43%) and 5c (52%). The mechanistic implications of the above…
Analysis of mebendazole binding to its target biomolecule by laser flash photolysis
2016
[EN] Mebendazole (MBZ) and related anticancer benzimidazoles act binding the beta-subunit of Tubulin (TU) before dimerization with alpha-TU with subsequent blocking microtubule formation. Laser flash photolysis (LFP) is a new tool to investigate drug-albumin interactions and to determine binding parameters such as affinity constant or population of binding sites. The aim of this study was to evaluate the interactions between the nonfluorescent mebendazole (MBZ) and its target biomolecule TU using this technique. Before analyzing the MBZ@TU complex it was needed to determine the photophysical properties of MBZ triplet excited state ((3)MBZ*) in different media. Hence, 3MBZ* showed a transien…
The triplet excited state of the biocative compound thiabendazole. Characterization and suitability as reporter for cyclodextrin complexation
2012
Fluorescence spectroscopy, laser flash photolysis (LPF), and density functional theory calculations have been performed to characterize the photobehavior of thiabendazole (1). Direct LFP of 1 results in the generation of a transient absorbing at λmax = 570 nm identified as the triplet excited state (31∗). The intersystem crossing quantum yield is 0.91, and the triplet energy is 288 kJ mol−1. The singlet–triplet energy gap is 84 kJ mol−1. The behavior of thiabendazole within CDs results in a marked enhancement of the triplet lifetime, this change is attributed to the mobility restrictions of included 1 imposed by the cyclodextrin cavities.