Photoinduced decarboxylations

Katagi T, Mikami N, Matsuda T, Miyamoto J (1989) Molecular orbital and experimental studies on the photoinduced decarboxylation of pyrethroid model esters. J Chem Soc Perkin Trans 2 779-782... 

The potassium salt of the 3-mercaptopropionic acid derivative 238 undergoes photoinduced decarboxylative cyclization to give the tricyclic product 239 in a low yield after prolonged irradiation (Equation 22)... 

JOC5590]. Photoinduced decarboxylative cyclisation has been applied to the preparation of the isoindolo-fused thiazepines 275 (m = 3 R = H, CH3) from the salts 274 [01EJO1831],... 

Griesbeck AG, Kramer W, Oelgemoller M (1999) Photoinduced Decarboxylation Reactions, Green Chem. August 205-207. 

Decarboxylation of excited singlets of aromatic esters (Eq. 13.6) is a concerted process, and it can account for a significant fraction of the reaction by appropriately substituted aryl esters, especially in bulk polymers and other media that are capable of imposing conformational constraints on guest molecules.Because photoinduced decarboxylation occurs before lysis of the aryl esters, it does not influence the rates at which the A B singlet pair react. For that reason, the relative yields of decarboxylation products need not be considered in analyses of the radical pairs unless their formation precludes sufficient radical pair production for their easy direct or indirect detection. 

The mechanism of the photoinduced decarboxylation of pyruvic acid has been reinvestigated and accounted for via electron transfer from an excited to a ground state molecule. Quantum yields of triplet production at 295 K in deoxygenated benzene, acetonitrile, and water are 0.65, 0.88, and 0.22, respectively. ... 

Grigorenko, B. L., Nemukhin, A. V., Morozov, D. I., Polyakov, I. V., Bravaya, K. B., Krylov, A. 1. [2012]. Toward Molecular-Level Characterization of Photoinduced Decarboxylation of the Green Fluorescent Protein Accessibility of the Chaise-Transfer States, / Chem. Theory Comp., 8, 1912-1920. 

Davidson, R. S. and Goodwin, D., The role of electron transfer process in the photoinduced decarboxylation reaction of a-oxocarboxylic acid, J. Chem. Soc., Perkin Trans. 2, 1559,1982. 

Gu, W., AbdaUah, D. J., and Weiss, R. G., Conformational control of photoinduced decarboxylation of simple aryl esters enhancement by templating effects in polyethylene Aims, /. Photochem. Photobiol A Chem., 139, 79, 2001. 

Griesbeck, A.G., OelgemoUer, M., Lex, J., Haeuseler, A., and Schmittel, M., Synthesis of sulfur-containing tricyclic ring systems by means of photoinduced decarboxylative cycUzations, Eur. J. 

Griesbeck, A.G., Kramer, W., and Oelgembller, M., Photoinduced decarboxylation reactions. Radical chemistry in water. Green Chem., 1, 205,1999. 

SET Pathways in the Photoinduced Decarboxylation of a-Heteroatom Substituted Carboxylates The Influence of Decarboxylation Rates on SET-Photoreactions of a-Amino Carboxylates... 

SET Pathways in the Photoinduced Decarboxylation of a-Heteroatom Substitnted Carboxylates... 

Davidson, R.S. and Steiner, P.R., Mechanism of the photoinduced decarboxylation of carboxylic acids sensitized by aromatic ketones and quinones,/. Chem. Soc., Perkin Trans. 2, 1357, 1972. 

The photolysis of carboxylic acids and derivatives as lactones, esters and anhydrides can yield decarboxylated products 253>. This reaction has been utilized in the synthesis of a-lactones from cyclic diacyl peroxides 254) (2.34) and in the synthesis of [2,2]paracyclophane by bis-decarboxylation of a lactone precursor (2.35) 255). This latter product was also obtained by photoinduced desulfurization of the analogous cyclic sulfide in the presence of triethyl phosphite 256). 

Photoinduced electron transfer from the carboxylate ion to the excited triplet phthalimide (fcT = 293-300 kj mol-1) appears to be followed by a rapid protonation of the radical anion and cyclization via a biradical recombination reaction (Scheme 9.1). Acetone (which also acts as photosensitizer) containing a small amount of water is the solvent of choice, whereas potassium carbonate is the ideal base to enhance cyclization versus simple decarboxylation and ring opening of the phthalimide [4]. 

Some fundamental aspects of polythiophene preparation and chemistry have been investigated. Solution processing of a polythiophene having ester groups has been performed, which after ester cleavage and decarboxylation gave new access to the parent thiophene polymer <07MAC6012>. The mechanism of the photoinduced polymerization of thiophene... 

Figure 9-10. Examples of photoinduced reactions in drug molecules. (I) Photoinduced isomerization (Ib), cyclization and enol-keto isomerization (Ic) of stilboestrol (la). (II) Photoinduced reactions of ketoprofen (Ila) and its degradation product (Ilb) decarboxylation (Ilb), reduction (lie), and dimerization (IIc) products of the drug. (Ill) A -dealkylation of methotrexate followed by oxidation. (IV) Dehalogenation (IVb) and photohydrolysis (IVc) of frusemide (IVa) [44].

The scope of this initiaticHi reaction may be widened by using an arylamino cetic acid derivative as the electron donor, with the same sensitisers, and of these indoI-3yl-acetic acid (lAA) is experimentally convenient. In these cases it is thought that the initiating radicals arise via decarboxylation following the normal photoinduced electron transfer. Quantum yields for initiation by the combination FL/DME, FL/IAA and NMA/IAA lie in the range 0.1—0.2 and it is clear that this technique affords a new versatile range of initiating systems for radical polymerization. 

The rates of polymerization of the CB/SCCA/acrylamide systems are affected by the yields of secondary processes that follow photoinduced electron transfer, e.g., decarboxylation or deprotonation. This is in addition to the reactivity of the free radicals themselves. 

Intramolecular photoinduced electron transfer in (58) leads to decarboxylation to give hydroxylactams in good yield (Griesbeck et al.), and irradiation of either the dextro or /eavo-rotatory crystals from the self-assembly of acridine and diphenyl acetic acid molecules, is reported to induce a decarboxylating condensation to give (+) or (—)-(59) with ees in the 35% region (Koshima et al,). The formation of ketones from the photolysis of nitrites is a low-yield process in... 

Photochemically generated radicals undergo a subsequent photoinduced or thermal oxidation to the corresponding carbocation. Faria and Steenken produced the triphenylmethyl radical through two-photon ionization and subsequent decarboxylation of the triphenylacetate ion. Laser excitation of the triphenylmethyl radical resulted in photoinjection of an electron to give the triphenylmethyl cation and a solvated electron [Eq. (8)] [91]. 

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