Yang Photocyclization: Coupling of Biradicals Formed by Intramolecular Hydrogen Abstraction of Ketones

Wagner, Peter J.

doi:10.1002/chin.200417282

Cited by 8 publications

(7 citation statements)

References 165 publications

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“…The generation of a 1,6 biradical was thus possible only if no hydrogen was present in either γor δpositions. 19,20,131 The Norrish-Yang coupling then resulted in the formation of the corresponding six-membered ring, as observed in the photochemical synthesis of variously substituted tetralols from βarylpropiophenones. 132 Vinyl radicals are widely used as intermediates in ring formation, and different generation strategies have been developed.…”

Section: Carbocyclesmentioning

confidence: 99%

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

2016

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The present review offers an overview of the current approaches for the photochemical and photocatalytic generation of reactive intermediates and their application in the formation of carbon-carbon bonds. Valuable synthetic targets are accessible, including arylation processes, formation of both carbo- and heterocycles, alpha- and beta-functionalization of carbonyls, and addition reactions onto double and triple bonds. According to the recent advancements in the field of visible/solar light catalysis, a significant part of the literature reported herein involves radical ions and radicals as key intermediates, with particular attention to the most recent examples. Synthetic application of carbenes, biradicals/radical pairs and carbocations have been also reported.

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Section: Carbocyclesmentioning

confidence: 99%

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

2016

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“…Furthermore, we propose that in the presence of oxygen, biradical 3 is intercepted to form peroxide 2 (Scheme 6). In addition, photolysis of 1 did not yield any products that can be attributed to intramolecular H atom abstraction of the c-H atom adjacent to the ester group (Hc) (32)(33)(34)(35), which is expected to yield o-methylacetophenone and the corresponding cyclobutanol (Scheme 7). Thus, intramolecular H atom abstraction from the ortho-methyl substituent must be more efficient than that from the ester alkyl chain in ester 1.…”

Section: Product Studiesmentioning

confidence: 99%

Photoenolization of o‐Methylvalerophenone Ester Derivative

Das

Lao

Guđmundsdóttir

2016

Photochem & Photobiology

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Photolysis of ester 1 in argon-saturated methanol and acetonitrile does not produce any product, whereas irradiation of 1 in oxygen-saturated methanol yields peroxide 2. Laser flash photolysis studies demonstrate that 1 undergoes intramolecular H atom abstraction to form biradical 3 (λmax ~340 nm), which intersystem crosses to form photoenols Z-4 and E-4 (λmax ~380 nm). Photoenols 4 decay by regenerating ester 1. With the aid of density functional theory calculations, it was concluded the photoenol E-4 does not undergo spontaneous lactonization or electrocyclic ring closure because the transition state barriers for these reactions are too large to compete with reketonization of E-4 to form 1.

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“…As an example, cycloalkanones undergo either a Norrish type I (path a) [6][7][8][9] or a Norrish type II (path b) [6][7][8][10][11][12][13] reaction affording diradicals that, in the latter case, may recombine via the well-known Norrish-Yang reaction [6,7,[10][11][12][13]. Diradicals are also intermediates in photoextrusion reactions (path c) [6,7] where the photorelease of a stable molecule, such as CO (in cyclic ketones) [14][15][16], dinitrogen (in azoalkanes) [17][18][19][20] or SO 2 (in sulfones, path c) [21], is followed by the concomitant radical-radical coupling of the radical sites in the resulting diradical.…”

Section: Introductionmentioning

confidence: 99%