Synthetic Applications of Photoinduced Electron Transfer Decarboxylation Reactions

Griesbeck, Axel G.; Krämer, Wolfgang; Oelgemöller, Michael

doi:10.1055/s-1999-3159

Cited by 83 publications

(51 citation statements)

References 20 publications

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“…The PEI was selected because it provides a hydrophobic shield [14] and acts as an ion stabilizer, i.e. as a catalyst for an electron transfer shuttle process [15]. The two protic non-solvents were selected because they act as diluents for forming the porous structure [16] and as a proton donor to enhance BMI polymerization.…”

Section: Membrane Preparationmentioning

confidence: 99%

Structuring and characterization of a novel highly microporous PEI/BMI semi-interpenetrating polymer network

Kurdi

Kumar

2005

Polymer

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Section: Membrane Preparationmentioning

confidence: 99%

Structuring and characterization of a novel highly microporous PEI/BMI semi-interpenetrating polymer network

Kurdi

Kumar

2005

Polymer

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“…10 The photodecarboxylation of phthalimide derivatives in particular has emerged as an efficient pathway to macrocycles and Grignard-type addition products (Scheme 1). 11,12 Due to the irreversible exclusion of carbon dioxide, these transformations proceed with quantum yields as high as 0.6 (i.e. 60% of all excited states populated generate a product molecule), thus resulting in short irradiation times and excellent light efficiencies.…”

Section: Results and Discussion Photodecarboxylations -'Photochemistrmentioning

confidence: 99%

Green Photochemical Processes and Technologies for Research & Development, Scale‐up and Chemical Production

Oelgemöller

2014

J Chinese Chemical Soc

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Photochemistry is often viewed as a green chemical method since photons are regarded as a 'clean and traceless reagent'. Despite this, photochemical transformations generally suffer from a variety of 'non-green' drawbacks that have prevented their widespread adaptation in chemical manufacturing. These include the necessity for hazardous solvents, low quantum yields of photochemical transformations, high energy demands of traditional lamps and the need for high dilution due to the low penetration of light into the reaction mixture. As a result, photochemical operations generate large volumes of hazardous solvent waste, demand prolonged irradiation times and require high energy inputs. This highlight article shows recent examples of green photochemical processes and technologies that overcome these limitations. These include photodecarboxylations in water matrices with high quantum yields in an advanced 308-nm excimer falling film reactor, solar photooxygenations utilizing concentrated sunlight generated in a parabolic trough loop and photosensitized additions in resource-efficient microreactors under continuous flow conditions. The results show that photochemistry can be implemented as a truly green methodology across the entire chemical process spectrum from early R&D to scale-up and subsequently production.

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“…6 In the previous decade we have developed this approach beyond the use of simple alkyl carboxylates (corresponding to imide alkylation) 7 to a-ketocarboxylates 8 and a-heteroatom substituted alkyl carboxylates. 9 Especially the latter variants show the potential of this reaction, i.e.…”

Section: Methodsmentioning

confidence: 99%

Photodecarboxylative Benzylation ofN-Alkylphthalimides: A Concise Route to the Aristolactam Skeleton

Griesbeck¹,

Warzecha²,

Neudörfl³

et al. 2004

Synlett

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The photoinitiated metal-free benzylation of N-alkyl phthalimides with arylacetates in aqueous solution followed by acid-catalyzed dehydration serves as a convenient route to methoxy-substituted precursors to phenanthrene lactam alkaloids.Aristolactams 1 I constitute a group of phenanthrene lactam alkaloids from the Aristolochia genus with promising pharmacological activities. While the corresponding nitrophenanthrene carboxylic acids, e.g. aristolochic acid IV (II R 6 = R 8 = OCH 3 , Figure 1), often found in the same plants, cause nephropathy with a high risk for urothelial cancer in humans (aristolochic acid nephropathy, AAN), 2 the aristolactams are potent inhibitors of platelet aggregation and show significant cytotoxicity against different tumor cell lines. Figure 1Structural variations of the natural aristolactams include methyl groups at the amide nitrogen, e.g. in the recently discovered piperolactam E (R 1 = R 2 = OCH 3 , R 3 = OH, R 4 = CH 3 ) 3 as well as a broad methoxy substitution pattern.A straightforward synthetic approach has been developed by the Couture group applying as key step the lithiation of halogenated N-phosphorylbenzamides, cyclization of the aryne intermediate, Horner olefination of the phosphorylated aminocarbanion and Pd-catalyzed arene-arene coupling. 4 We wish to describe an alternative photochemical concept. Since a direct oxidative arene coupling also appears feasible for the isoindolinone case, i.e. for the phenanthrene ring closure (A → I), we envisaged the synthesis of arylalkylidene isoindolinones A with the appropriate Ealkene configuration (Scheme 1). Consequently, the benzylation of symmetric phthalimides C with arylacetic acids D and subsequent acid-catalyzed dehydration of the 3-benzyl-3-hydroxyisoindolin-1-ones B appears as a short and simple approach to the desired stilbene skeletons. Moreover, a straightforward access to both A and B is of general interest due to their biological potential. 5 Scheme 1The photodecarboxylative addition of alkyl carboxylates to N-substituted phthalimides via photoinduced electron transfer (PET) represents a metal-free variant of the traditional Grignard-type alkylation of phthalimides. 6 In the previous decade we have developed this approach beyond the use of simple alkyl carboxylates (corresponding to imide alkylation) 7 to a-ketocarboxylates 8 and a-heteroatom substituted alkyl carboxylates. 9 Especially the latter variants show the potential of this reaction, i.e. solely the carboxylate group is activated after the primary electronic excitation of the phthalimide chromophore and these processes can easily be upscaled to the 20-40 g scale by applying excimer radiation technology. 10 As we have already demonstrated, 7,10 benzylation of N-methylphthalimide with phenylacetate is a straightforward and highyielding process.A synthetically relevant as well as mechanistically appealing question was whether this pivotal benzylation step tolerates additional electron-donating substituents at both arene components, i.e. the phthalimide subs...

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Synthetic Applications of Photoinduced Electron Transfer Decarboxylation Reactions

Cited by 83 publications

References 20 publications

Structuring and characterization of a novel highly microporous PEI/BMI semi-interpenetrating polymer network

Structuring and characterization of a novel highly microporous PEI/BMI semi-interpenetrating polymer network

Green Photochemical Processes and Technologies for Research & Development, Scale‐up and Chemical Production

Photodecarboxylative Benzylation ofN-Alkylphthalimides: A Concise Route to the Aristolactam Skeleton

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