Stereoselective Triplet‐Sensitised Radical Reactions of Furanone Derivatives

Jahjah, Rabih; Gassama, Abdoulaye; Bulach, Véronique; Suzuki, Takayuki; Abe, Manabu; Hoffmann, Norbert; Martinez, Agathe; Nuzillard, Jean‐Marc

doi:10.1002/chem.200903045

Cited by 44 publications

(64 citation statements)

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“…Mechanistically, addition reactions of this type can occur as a radical chain reaction because the addition product of the α-aminoalkyl radical is a carbon-centered radical, which can abstract a hydrogen atom from the tertiary amine [29–30]. Notable contributions to the field of direct tertiary amine addition reactions to enones were made by Hoffmann et al, who established the use of aromatic ketones as suitable PET catalysts for these reactions [31–37]. In Scheme 1, the addition reaction of N , N -dimethylaniline ( 1 ) to (5 R )-menthyloxyfuran-2(5 H )-one ( 2 ) is shown, which proceeds to the intriguing tricyclic product 4 employing 4,4’-bis(dimethylamino)benzophenone ( 3 ) as the catalyst [38].…”

Section: Introductionmentioning

confidence: 99%

Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds

Lenhart¹,

Bach²

2014

Beilstein J. Org. Chem.

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Summary N-Methyl-N-((trimethylsilyl)methyl)aniline was employed as reagent in visible-light-induced, iridium-catalyzed addition reactions to cyclic α,β-unsaturated carbonyl compounds. Typical reaction conditions included the use of one equivalent of the reaction substrate, 1.5 equivalents of the aniline and 2.5 mol % (in MeOH) or 1.0 mol % (in CH2Cl2) [Ir(ppy)2(dtbbpy)]BF4 as the catalyst. Two major reaction products were obtained in combined yields of 30–67%. One product resulted from aminomethyl radical addition, the other product was a tricyclic compound, which is likely formed by attack of the intermediately formed α-carbonyl radical at the phenyl ring. For five-membered α,β-unsaturated lactone and lactam substrates, the latter products were the only products isolated. For the six-membered lactones and lactams and for cyclopentenone the simple addition products prevailed.

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Section: Introductionmentioning

confidence: 99%

Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds

Lenhart¹,

Bach²

2014

Beilstein J. Org. Chem.

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“…However, the transfer may also occur from the 6′ position of the tetrahydropyranyl substituent. The competition of these two reactions was observed when an alkyl substituent was attached to the side chain of the furanone derivative 34 (Scheme 6) [78]. A 1:1 mixture of diastereoisomers of 34 (center 2′ of the tetrahydropyranyl group with respect to the center 5 of the furanone moity) was transformed.…”

Section: Intramolecular Radical Addition With Electronically Excited mentioning

confidence: 98%

“…In α,β-unsaturated lactones (furanones) such as 27, the amine was replaced by such a function (Scheme 5) [78]. The furanone is electronically excited by triplet sensitization with acetone.…”

Section: Intramolecular Radical Addition With Electronically Excited mentioning

confidence: 99%

“…The influence of an alkyl substituent at the side chain is well understood. The 3 ππ* excited and vibrationally relaxed state of the furanone moieties has been modeled with structures 54 and 55 (Scheme 10) [78]. Transition states for the hydrogen abstraction at the anomeric center (2′ position) leading to structure 56 and at the 6′ position leading to structure 57 have been calculated.…”

Section: Intramolecular Radical Addition With Electronically Excited mentioning

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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“…上述的 1,4-加成反应都是通过单电子转移过程发生的, 但一些新研究表明, 如果一旦含氧化合物 α-H 抽取后电子与质子同时发生转移形成一个双自由基中间体, 则会形成 2(5H)-呋喃酮 α 位加成产物(Scheme 5) [14] .…”

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