scholarly journals Photooxidation of 2-(tert-Butyl)-3-Methyl-2,3,5,6,7,8-Hexahydroquinazolin-4(1H)-one, an Example of Singlet Oxygen ene Reaction

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5008
Author(s):  
Adrian Méndez ◽  
Jonathan Román Valdez-Camacho ◽  
Jaime Escalante
Keyword(s):  
Singlet Oxygen ◽  
Theoretical Study ◽  
Solvent Mixture ◽  
Ambient Conditions ◽  
Ene Reactions ◽  
Ene Reaction ◽  
Photo Oxidation ◽  
Tert Butyl ◽  
Nmr Study ◽  
Step Mechanism

Singlet oxygen ene reactions produce 2-(tert-butyl)-4a-hydroperoxy-3-methyl-2,4a, 5,6,7,8-hexahydroquinazolin-4(3H)-one quantitatively during diffusion crystallization of 2-(tert-butyl)-3-methyl-2,3,5,6,7,8-hexahydroquinazolin-4(1H)-one in n-hexane/CH2Cl2 solvent mixture. To confirm this photo-oxidation, a 1H-NMR study in CDCl3 was performed with exposure to ambient conditions (light and oxygen), with neither additional reactants nor catalysts. A theoretical study at the B3LyP/6311++G** level using the QST2 method of locating transition states suggests a two-step mechanism where the intermediate, which unexpectedly did not come from the peroxide intermediate, has a low activation energy.

Article

1998 ◽  
Vol 76 (12) ◽  
pp. 1805-1816
Author(s):  
L Ross C Barclay ◽  
Jennifer K Grandy ◽  
Heather D MacKinnon ◽  
Heather C Nichol ◽  
Melinda R Vinqvist
Keyword(s):  
Oxygen Uptake ◽  
Singlet Oxygen ◽  
Sodium Azide ◽  
Lignin Content ◽  
Sodium Dodecyl ◽  
Kinetic Studies ◽  
Product Distribution ◽  
Geometrical Isomers ◽  
Photo Oxidation ◽  
Tert Butyl

3,5-Di-tert-butyl-ortho-quinone, 6, and 1-(3,4-dimethoxyphenyl-2-(2-methoxyphenoxy)-1-propanone, 7, models for oxidized lignin and for lignin, were used as sensitizers of photo-oxidation. Product studies by HPLC from oxidation of methyl linoleate in solution sensitized by 6 or 7, and in sodium dodecyl sulfate (SDS) sensitized by 6, showed a product distribution of six hydroperoxides, the four conjugated 9- and 13-hydroperoxides of the geometrical isomers: trans-10, cis-12 (2), cis-9, trans-11 (3), trans-10, trans-12 (4), and trans-9, trans-11 (5)-octadecadienoates plus two nonconjugated hydroperoxides. The higher cis/trans to trans/trans (ct/tt) of geometrical isomers (2 + 3//4 + 5) compared to ct/tt from known thermal free-radical peroxidations (Type 1) indicate that singlet oxygen (Type 2) oxidation occurs in reactions sensitized by 6 or 7. Kinetic studies by oxygen uptake are reported on oxidations of hydrocarbons 1-phenyl-2-methylpropene,8, and trans-stilbene,9, sensitized by the quinone, 6, or by a dye, Rose Bengal. Quenching studies imply singlet oxygen reactions. Milled wood lignin undergoes self-initiated photo-oxidation in water, and oxygen uptake was quenched by sodium azide. Cellobiose, a cellulose model, undergoes sensitized photo-oxidation using model quinone, 6, in a mixture of tert-butyl alcohol and water or using the sensitizers benzophenone or the lignin model, 7, delivered on a solid support, silica gel, and these oxidations were quenched with sodium azide. These results implicate singlet oxygen in the photo-yellowing of high lignin content wood pulps.Key words: lignin models, ortho-quinone, photo-oxidation, singlet oxygen, lignin, cellobiose.

scholarly journals Theoretical Study of the Reaction Formalhydrazone with Singlet Oxygen. Fragmentation of the C=N Bond, Ene Reaction and Other Processes

2013 ◽  
Vol 90 (2) ◽  
pp. 431-438 ◽  
Author(s):  
Benjamin Rudshteyn ◽  
Álvaro Castillo ◽  
Ashwini A. Ghogare ◽  
Joel F. Liebman ◽  
Alexander Greer
Keyword(s):  
Singlet Oxygen ◽  
Theoretical Study ◽  
Ene Reaction

DNA-porphyrin hybrids as reaction centers for photosensitized ene reactions with singlet oxygen

2012 ◽  
Vol 16 (05n06) ◽  
pp. 488-498 ◽  
Author(s):  
Rüdiger Haug ◽  
Helmut Griesser ◽  
Thomas Sabirov ◽  
Clemens Richert
Keyword(s):  
Singlet Oxygen ◽  
Solid Phase ◽  
Product Distribution ◽  
Reaction Centers ◽  
Ene Reactions ◽  
Ene Reaction ◽  
Reaction Solution ◽  
Starting Point ◽  
Recent Developments ◽  
Set Up

Recent developments in DNA-mediated nanostructuring have paved the way for the development of novel reaction centers. As part of a project focused on nanostructured reaction centers for reactions catalyzed by porphyrins, we have developed a solid-phase synthesis of tetrakis(p-hydroxyphenyl)porphyrin-oligonucleotide hybrids. In these hybrids, up to four nucleic acid chains are linked to the phenolic substituents of the porphyrin via phosphodiester linkages. A representative hybrid with one oligonucleotide chain of the sequence TTAA was found to survive light irradiation under aerobic conditions for 2 h with less than 35% oxidation of the DNA chain. An assay measuring the diastereo- and enantioselectivity of the photosensitized ene reaction of mesitylol with singlet oxygen was set up that provides diastereomeric ratios via NMR of aliquots of the reaction solution. Enantiomers were separated gas chromatographically on a chiral stationary phase and were assigned based on the product distribution obtained with an enantiomerically enriched starting material. Our results are a starting point for the exploration of nanostructured reaction media based on DNA and porphyrins.

Photo-oxidation of lipids by singlet oxygen: a theoretical study

2004 ◽  
Vol 398 (4-6) ◽  
pp. 336-342 ◽  
Author(s):  
Ismael Tejero ◽  
Angels González-Lafont ◽  
José M. Lluch ◽  
Leif A. Eriksson
Keyword(s):  
Singlet Oxygen ◽  
Theoretical Study ◽  
Photo Oxidation

Photooxygenation in polymer matrices: En route to highly active antimalarial peroxides

2005 ◽  
Vol 77 (6) ◽  
pp. 1059-1074 ◽  
Author(s):  
Axel G. Griesbeck ◽  
Tamer T. El-Idreesy ◽  
Anna Bartoschek
Keyword(s):  
Singlet Oxygen ◽  
Protoporphyrin Ix ◽  
Polymer Matrices ◽  
Allylic Alcohols ◽  
Ene Reaction ◽  
Highly Active ◽  
Determining Factors ◽  
Broad Variety ◽  
Covalently Linked

Photooxygenation involving the first excited singlet state of molecular oxygen is a versatile method for the generation of a multitude of oxy-functionalized target molecules often with high regio- and stereoselectivities. The efficiency of singlet-oxygen reactions is largely dependent on the nonradiative deactivation paths, mainly induced by the solvent and the substrate intrinsically. The intrinsic (physical) quenching properties as well as the selectivity-determining factors of the (chemical) quenching can be modified by adjusting the microenvironment of the reactive substrate. Tetraarylporphyrins or protoporphyrin IX were embedded in polystyrene (PS) beads and in polymer films or covalently linked into PS during emulsion polymerization. These polymer matrices are suitable for a broad variety of (solvent-free) photooxygenation reactions. One specific example discussed in detail is the ene reaction of singlet oxygen with chiral allylic alcohols yielding unsaturated β-hydroperoxy alcohols in (threo) diastereoselectivities, which depended on the polarity and hydrogen-bonding capacity of the polymer matrix. These products were applied for the synthesis of mono- and spirobicyclic 1,2,4-trioxanes, molecules that showed moderate to high antimalarial properties. Subsequent structure optimization resulted in in vitro activities that surpassed that of the naturally occurring sesquiterpene-peroxide artemisinin.

Sign in / Sign up

Export Citation Format

Share Document