Mechanistic Models of Asymmetric Reductions

Ohno, Atsuyoshi; Ushida, Satoshi

doi:10.1007/978-1-4899-3123-8

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“…When BNAH was replaced by the 4-monodeuteriated compound (['H,]BNAH), the quantum yield was reduced by a factor of 1.6, i.e., C~(BNAH)/~([~H,]BNAH) = 1.61 & 0.05. This value corresponds to the kinetic isotope effect, cpH/cpD = 4.1 k 0.6, which is obtained from equation (4), where the secondary The cp values of PhCOCH,Br are larger than those of PhCOCH,CI, and both the cp values are constant with a change in the AcrH, concentration. On the other hand, the cp value increases with an increase in the PhCOCH,X concentration to approach a constant value at high concentrations as shown in Figure 2.…”

Section: Resultsmentioning

confidence: 99%

Photoreduction of phenacyl halides by NADH analogues. Origins of different mechanistic pathways

Fukuzumi¹,

Mochizuki²,

Tanaka³

1989

J. Chem. Soc., Perkin Trans. 2

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Photoreduction of phenacyl halides (PhCOCH,X) by an NADH analogue, 10-methyl-9-acridone (AcrH,) in acetonitrile (MeCN) under irradiation of light ( h > 320 nm) proceeds via the rate-determining photoinduced electron transfer from the singlet excited state of AcrH, to PhCOCH,X to give the radical ion pair (AcrH2' PhCOCH,X-'). The subsequent fast reaction is completed within the complex by prqton transfer from AcrH,+' to PhCOCH,X-', followed by electron transfer from AcrH' t o PhC(OH)CH,X, yielding 1 0-methylacridinium ion (AcrH') and acetophenone (PhCOCH,). However, photoreduction of PhCOCH,X by another NADH analogue, 1 -benzyl-l,4-dihydronicotinamide (BNAH), in MeCN under irradiation with visible light of h >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 PhCOCH,X. The origins of these different mechanistic pathways dependent on the NADH analogues are

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Section: Resultsmentioning

confidence: 99%