Journal ArticleDOI
Stereoselectivity of Triplet Photocycloadditions:1 Diene−Carbonyl Reactions and Solvent Effects
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In this article, the diastereoselectivity of the photocycloaddition of benzaldehyde to furan was determined (exo/endo = 212:1) and compared with the reaction of other carbonyls compounds and carbonyl analogues.Abstract:
The diastereoselectivity of the photocycloaddition of benzaldehyde to furan was determined (exo/endo = 212:1) and compared with the reaction of other carbonyl compounds and carbonyl analogues. These results were compared with Paterno−Buchi reactions of cycloalkenes and cyclic enol ethers. An increase in steric demand of the α-substituent in benzoyl compounds led to a change in exo/endo-selectivity for furan cycloadditions that was not observed for cycloalkenes or cyclic enol ethers. Different ISC-reactive conformers with enhanced spin−orbit coupling are postulated as a reasonable explanation for the stereoselectivities observed. Additionally, solvent effects were studied, demonstrating the influence of photoinduced electron-transfer steps on the regio- and diastereoselectivity of Paterno−Buchi reactions with 2,3-dihydrofuran in polar solvents. Two bicyclic oxetanes (8 and 10) were characterized by X-ray structure analysis.read more
Citations
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Journal ArticleDOI
Selectivity control in electron spin inversion processes: regio- and stereochemistry of Paternò-Büchi photocycloadditions as a powerful tool for mapping intersystem crossing processes.
TL;DR: The higher selectivity observed for triplet reactions is rationalized by the optimal conformations of the intermediate 2-oxabutane-1,4-diyls for intersystem crossing to the singlet manifold, controlled preferentially by spin-orbit coupling.
Journal ArticleDOI
The Paternò-Büchi reaction - a comprehensive review.
TL;DR: The photochemical reaction between an excited state of carbonyl compounds and an alkene to give the oxetane deriving from a cycloaddition reaction (the Paternò-Büchi reaction) is presented, and the possible application of this reaction in organic synthesis is discussed, comparing the photochemical approach with the other approaches used to synthesize theOxetane ring.
Journal ArticleDOI
Oxetane synthesis through the Paternò-Büchi reaction
Maurizio D'Auria,Rocco Racioppi +1 more
TL;DR: In this review the mechanism of the Paternò-Büchi reaction is discussed, and the reported applications of this reaction to the synthesis of naturally occuring compounds are pointed out.
Journal ArticleDOI
Diastereo‐ and Enantioselective Synthesis of Pyrrolo[1,4]benzodiazepines through Decarboxylative Photocyclization
TL;DR: Memory of chirality in triplet 1,7-diradicals was detected for the first time and to a remarkably high degree in the decarboxylative photocyclization of the proline derivative of N-phthaloyl anthranilic acid 1 into 2.
Journal ArticleDOI
The Paternò-Büchi reaction—Mechanisms and application to organic synthesis
Maxime Fréneau,Norbert Hoffmann +1 more
TL;DR: In this article, the Paterno-Buchi reaction has been applied as a key step in various multi-step syntheses and its properties have been discussed as a consequence of the reaction mechanism.
References
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Dieter Rehm,Albert Weller +1 more
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Photoinduced Electron Transfer in Solution: Exciplex and Radical Ion Pair Formation Free Enthalpies and their Solvent Dependence
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Lionel Salem,Colin Rowland +1 more
TL;DR: In this paper, a review of the various possible definitions of diradicals leads the authors to describe these systems as having two odd electrons in degenerate or nearly-degenerate molecular orbitals.
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Local polarity of solvent mixtures in the field of electronically excited molecules and exciplexes
TL;DR: In this paper, the authors show that in non-viscous liquid media dielectric enrichment reaches equilibrium in times of 1 ns to over 20 ns depending on the polar solvent mole fraction in the mixture.