Photoaddition Reactions of Acetylpyridines with Silyl Ketene Acetals: SET vs [2+2]-Cycloaddition Pathways

Title
Photoaddition Reactions of Acetylpyridines with Silyl Ketene Acetals: SET vs [2+2]-Cycloaddition Pathways
Author(s)
조대원박혜정[박혜정]윤웅찬[윤웅찬]이향렬[이향렬]조대원Patrick Mariano[Patrick Mariano]
Keywords
SINGLE-ELECTRON-TRANSFER; AROMATIC CARBONYL-COMPOUNDS; PHOTOCYCLIZATION REACTIONS; SUBSTITUTED PYRIDINES; MICHAEL REACTIONS; ORGANIC-SYNTHESIS; CATION RADICALS; CROWN-ETHERS; RICH ALKENES; ALLYLSILANES
Issue Date
201211
Publisher
AMER CHEMICAL SOC
Citation
JOURNAL OF ORGANIC CHEMISTRY, v.77, no.22, pp.10304 - 10313
Abstract
Photoaddition reactions of silyl ketene acetals with 2-, 3- and 4-acetylpyridine have been explored. The results show that the acetylpyridines react with an electron rich, dimethyl-substituted silyl ketene acetal via a pathway in which excited state single electron transfer (SET) takes place to produce beta-hydroxyesters in high yields. In contrast, photochemical reactions of the acetylpyridines with an electron deficient, nonmethyl-substituted silyl ketene acetal generate oxetanes as major products, which arise via a route involving excited state [2 + 2]-cycloaddition. In addition, an increase in solvent polarity significantly enhances the relative efficiencies of the SET processes versus [2 + 2]-cycloaddition reactions. Importantly, the carbonyl groups rather than the pyridine moieties in the acetylpyridine substrates participate in both types of addition reactions. Finally, the results demonstrate that photoinduced electron transfer (PET)-promoted chemical reactions between acetylpyridines and electron rich silyl ketene acetals in polar solvent serve as useful methods to promote beta-hydroxyester forming, Claisen or Mukaiyama condensation reactions under mild conditions.
URI
http://hdl.handle.net/YU.REPOSITORY/27014http://dx.doi.org/10.1021/jo301961n
ISSN
0022-3263
Appears in Collections:
이과대학 > 화학생화학부 > Articles
문과대학 > 중국언어문화학과 > Articles
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