Microflow Photochemistry - Acetone sensitized Addition of Isopropanol to (5R)-5-Menthyloxy-2-(5H)-furanone

Aida, Shin; Nishiyama, Yasuhiro; Kakiuchi, Kiyomi; Hoffmann, Norbert; Fon, Adeline; Oelgemöller, Michael

doi:10.5857/rcp.2013.2.3.68

Cited by 3 publications

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“…Due to its efficiency, the acetone sensitized addition of secondary alcohols to furanones was used as a model reaction to characterize and to compare different photochemical microreactor systems [41,42]. In order to be able to achieve more coherent results, 4,4′-dimethoxybenzophenone (DMBP) was used as a more effective sensitizer.…”

Section: Intermolecular Radical Addition As a Standard Reaction To Evmentioning

confidence: 99%

“…Such electron donor substituted aromatic ketones have also been applied successfully to the photochemically induced radical addition of tertiary amines to electron deficient alkenes [43,44]. Thus the 4,4′-dimethoxybenzophenone (DMBP) photosensitized addition of secondary alkohols to a series of furanones was selected as a model transformation for a detailed reactor comparison study (Scheme 2) [41,42,45,46].…”

Section: Intermolecular Radical Addition As a Standard Reaction To Evmentioning

confidence: 99%

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Photochemically induced radical reactions with furanones

Oelgemöller

Hoffmann

2015

Pure and Applied Chemistry

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Radicals are easily generated via hydrogen transfer form secondary alcohols or tertiary amines using photochemical sensitization with ketones. They can subsequently add to the electron deficient double bond of furanones. The addition of the alcohols is particularly efficient. Therefore, this reaction was used to characterize and to compare the efficiency of different photochemical continuous flow microreactors. A range of micro-structured reactors were tested and their performances evaluated. The enclosed microchip enabled high space-time-yields but its microscopic dimensions limited its productivity. In contrast, the open microcapillary model showed a greater potential for scale-up and reactor optimization. A 10-microcapillary reactor was therefore constructed and utilized for typical R&D applications. Compared to the corresponding batch processes, the microreactor systems gave faster conversions, improved product qualities and higher yields. Similar reactions have also been carried out with electronically excited furanones and other α,β-unsaturated ketones. In this case, hydrogen is transferred directly to the excited olefin. This reaction part may occur either in one step, i.e., electron and proton are transferred simultaneously, or it may occur in two steps, i.e., the electron is transferred first and the proton follows. In the first case, a C-C bond is formed in the α position of the α,β-unsaturated carbonyl compound and in the second case this bond is formed in the β position. For the first reaction, the influence of stereochemical elements of the substrate on the regioselectivity of the hydrogen abstraction on the side chain has been studied.

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Section: Intermolecular Radical Addition As a Standard Reaction To Evmentioning

confidence: 99%

Section: Intermolecular Radical Addition As a Standard Reaction To Evmentioning

confidence: 99%

Photochemically induced radical reactions with furanones

Oelgemöller

Hoffmann

2015

Pure and Applied Chemistry

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Electron and hydrogen transfer in organic photochemical reactions

Hoffmann

2014

J of Physical Organic Chem

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Electron and hydrogen transfers are basic steps in many chemical reactions. Photochemical or electronic excitation significantly influences the reactivity of chemical compounds and thus also these transfer processes. Furthermore, the formation of typical intermediates has a decisive impact on the outcome of the transformations. Based on these properties of photochemical processes, efficient homogeneous and heterogeneous photocatalytic transformations for application to organic synthesis have been developed. Efficient reactions without any chemical activation but induced by photochemical electron transfer can also be carried out. The photon acts as a traceless reagent. In the context of photochemical hydrogen transfer, two processes are frequently encountered. The two particles the electron and the proton are transferred either simultaneously or in two steps. In the latter case, the electron is transferred first and the proton follows. Both processes are applied to organic synthesis. Copyright © 2014 John Wiley & Sons, Ltd.

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The structure of electronically excited α,β‐unsaturated lactones

Fréneau

Sainte-Claire

Abe

et al. 2016

J of Physical Organic Chem

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A better knowledge of the structure of the electronically excited state of substrates is indispensable for the understanding and optimization of photochemical reactions. For this study, triplet energies of a variety of α,β-unsaturated γ-lactones (furanones) as well as the structures of the vibrationally relaxed triplet state (T 1 ) have been determined using ab initio coupled-cluster (CCSD) method and/or density functional theory (DFT) calculation. A twist of the original planar structure around C = C bond is found in the relaxed triplet state, π-π*. In the 5-membered ring of furanones the contribution of this mode is limited and the pyramidalization in the C 4 position also contributes to the stabilization. The contribution of each stabilization mode is characterized by the dihedral angles and the Mulliken atomic spin densities. The substituent effect on the pyramidalization and the spin density distribution in the C 4 and in the C 5 position are reported. Depending on the substitution in the C 4 position, the orientation of the pyramidalization is either favored syn or anti with respect of the hydroxyl substituent in the C 5 position. Figure 3. Energies of different electronic states for furanone 1. Structures were optimized in the ground state (left-hand side) and in the T 1 state (right-hand side) at the B3LYP/6-31G(d,p) level. Energies for the higher excited states, T 2 , S 1 , and S 2 , were calculated using TD-DFT Chart 1. Model compounds chosen for the computational study. M. FRÉNEAU ET AL. wileyonlinelibrary.com/journal/poc

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Microflow Photochemistry - Acetone sensitized Addition of Isopropanol to (5R)-5-Menthyloxy-2-(5H)-furanone

Cited by 3 publications

References 19 publications

Photochemically induced radical reactions with furanones

Photochemically induced radical reactions with furanones

Electron and hydrogen transfer in organic photochemical reactions

The structure of electronically excited α,β‐unsaturated lactones

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