Photoreduction of phenacyl halides by NADH analogues. Origins of different mechanistic pathways
- 1 January 1989
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 10,p. 1583-1589
- https://doi.org/10.1039/p29890001583
Abstract
Photoreduction of phenacyl halides (PhCOCH2X) by an NADH analogue, 10-methyl-9-acridone (AcrH2) in acetonitrile (MeCN) under irradiation of light (λ > 320 nm) proceeds via the rate-determining photoinduced electron transfer from the singlet excited state of AcrH2 to PhCOCH2X to give the radical ion pair (AcrH2 +˙ PhCOCH2X–˙). The subsequent fast reaction is completed within the complex by proton transfer from AcrH2 +˙ to PhCOCH2X–˙, followed by electron transfer from AcrH˙ to PhĊ(OH)CH2X, yielding 10-methylacridinium ion (AcrH+) and acetophenone (PhCOCH3). However, photoreduction of PhCOCH2X by another NADH analogue, 1-benzyl-1,4-dihydronicotinamide (BNAH), in MeCN under irradiation with visible light of λ >360 nm proceeds by a different reaction pathway; electron-transfer radical chain reactions, in which the chain carrier radicals are produced by photoinduced electron transfer from the singlet excited state of BNAH to PhCOCH2X. The origins of these different mechanistic pathways dependent on the NADH analogues are discussed.Keywords
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