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Photodecarboxylation of benzoyl-substituted biphenylacetic acids and photo-retro-Aldol reaction of related compounds in aqueous solution. Acid and base catalysis of reaction

Paper ID Volume ID Publish Year Pages File Format Full-Text
27971 44053 2009 11 PDF Available
Title
Photodecarboxylation of benzoyl-substituted biphenylacetic acids and photo-retro-Aldol reaction of related compounds in aqueous solution. Acid and base catalysis of reaction
Abstract

To further explore the structural effects on efficiency of photodecarboxylation of Ketoprofen-type molecules the photodecarboxylation of two “extended” benzoyl-substituted acetic acids, 3′-benzoyl and 4′-benzoyl-4-biphenylacetic acids (2 and 3, respectively) have been studied in aqueous solution. In these systems, the benzoyl or benzophenone activating chromophore is distal to the phenylacetic acid moiety, separated by a phenyl spacer. Both of these compounds were found to undergo efficient (Φ = 0.3–0.7) photodecarboxylation in solutions of various pHs, giving rise to very broad long wavelength transient absorptions in laser flash photolysis studies (at pH > pKa) that have been assigned as the corresponding highly conjugated benzylic carbanions/enolates. The photodecarboxylation of the corresponding parent benzophenone systems was also studied as a function of pH for comparison as are two photo-retro-Aldol reactions of benzophenone alcohols. Photo-retro-Aldol reaction requires base-catalysis but surprisingly, photodecarboxylation can also be mediated in acidic pH for some of the studied phenylacetic acids. The acid-catalyzed pathway requires prior protonation of the photoexcited benzophenone oxygen and has precedent in the acid catalyzed photohydration and intramolecular photoredox chemistry of benzophenones. These and other new mechanistic insights discovered in this work show that the benzophenone chromophore can activate decarboxylation over much longer molecular distances as well as induce new types of ionic chemistry.

Keywords
Benzyl carbanion; Acid catalyzed photodecarboxylation; Photo-retro-Aldol; Extended enols/enolates
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Photodecarboxylation of benzoyl-substituted biphenylacetic acids and photo-retro-Aldol reaction of related compounds in aqueous solution. Acid and base catalysis of reaction
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 204, Issue 1, 30 April 2009, Pages 52–62
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us