Synthetic applications of photoinduced electron transfer decarboxylation reactions

Griesbeck, Axel G., Kramer, Wolfgang, and Oelgemoeller, Michael (1999) Synthetic applications of photoinduced electron transfer decarboxylation reactions. Synlett, 7. pp. 1169-1178.

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Photoinduced electron transfer (PET) decarboxylation of alkyl carboxylates in water leads to primary, secondary or tertiary carbon radicals which undergo C-C coupling reactions either in an intra- or intermolecular fashion. Intramolecular coupling gives rise to heterocyclic ring systems (lactams, lactones, cyclopeptides, cyclic ethers, crown ethers) with ring sizes from 5 to 28 and a broad variety of functionalities. Intermolecular coupling gives Grignardtype adducts (but with different chemo- and regioselectivities as for carbanion reactions). Yields of these reactions are mostly high, dilution conditions are not necessary, quantum yields are in the range of 0.5-0.6, and chemo- as well as regioselectivities are excellent. The electron-accepting chromophores which have been investigated are the imides of phthalic, maleic, quinolinic and trimellitic acid. Selectivity can be further controlled by two simple tricks:

- Only triplet excited acceptors are active in these electron-transfer reactions, thus sensitization excludes other (homolytic) pathways;

- Donor groups (SR, NR₂, aryl, OR, C=C) other than the carboxylate can be activated by lowering the pH (and thus protonating the COO-donor).

In intramolecular reactions, substrate concentration up to 0.1 M were applied successfully and the reactions were completed in 10-12 h for multigram conversions.

Item ID: 29976
Item Type: Article (Research - C1)
ISSN: 1437-2096
Keywords: photodecarboxylation, phthalimides, chirality memory, alkali metal carboxylates, α-keto carboxylates, macrocyclization
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Date Deposited: 22 Mar 2014 06:42
FoR Codes: 03 CHEMICAL SCIENCES > 0305 Organic Chemistry > 030503 Organic Chemical Synthesis @ 40%
03 CHEMICAL SCIENCES > 0305 Organic Chemistry > 030504 Organic Green Chemistry @ 30%
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