- Stereochemically probing the photo-favorskii rearrangement: A mechanistic investigation
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Using model (R)-2-acetyl-2-phenyl acetate esters of (S)- or (R)-α-substituted-p-hydroxybutyrophenones (S,R)-12a and (R,R)-12b, we have shown that a highly efficient photo-Favorskii rearrangement proceeds through a series of intermediates to form racemic rearrangement products. The stereogenic methine on the photoproduct, rac-2-(p-hydroxyphenyl)propanoic acid (rac-9), is formed by closure of a phenoxy-allyloxy intermediate 17 collapsing to a cyclopropanone, the Favorskii intermediate 18. These results quantify the intermediacy of a racemized triplet biradical 316 on the major rearrangement pathway elusively to the intermediate 18. Thus, intersystem crossing from the triplet biradical surface to the ground state generates a planar zwitterion prior to formation of a Favorskii cyclopropanone that retains no memory of its stereochemical origin. These results parallel the mechanism of Dewar and Bordwell for the ground state formation of cyclopropanone 3 that proceeds through an oxyallyl zwitterionic intermediate. The results are not consistent with the stereospecific SN2 ground state Favorskii mechanism observed by Stork, House, and Bernetti. Interconversion of the diastereomeric starting esters of (S,R)-12a and (R,R)-12b during photolysis did not occur, thus ruling out leaving group return prior to rearrangement.
- Givens, Richard S.,Rubina, Marina,Stensrud, Kenneth F.
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p. 1709 - 1717
(2013/03/28)
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- Synthesis of a series of novel 2,4,5-trisubstituted selenazole compounds as potential PLTP inhibitors
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Based on a homology-modeled structure of PLTP and characteristic structural features of reported cholesteryl ester transfer protein (CETP) inhibitors, we designed and synthesized a novel series of 2,4,5-trisubstituted selenazole compounds. Biological evaluation reveals that compounds 12 and 17 exhibit favorable PLTP activity, and their IC50s are 8 μM and 10 μM, respectively.
- Ling, Cui,Zheng, Zhibing,Jiang, Xian Cheng,Zhong, Wu,Li, Song
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scheme or table
p. 5123 - 5125
(2010/10/19)
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