Photoinduced Decarboxylative Benzylation of Phthalimide Triplets with Phenyl Acetates:  a Mechanistic Study

Abstract

The photodecarboxylative benzylation of N-alkyl, N-arylalkyl, and N-aryl phthalimides with arylacetic acids in aqueous solution proceeds via electron transfer from the arylalkanoate to the excited triplet state of the phthalimide, either formed directly or upon sensitization with acetone. The rate constant for triplet quenching of N-methylphthalimide is k(q) < 10(7) M(-1) s(-1) for 2-phenylacetic acid and k(q) = (1-3) x 10(9) M(-1) s(-1) for its mono-, di- and trimethoxy-substituted derivatives, suggesting a change of the mechanism for the primary oxidation step from a Photo-Kolbe type reaction yielding an acyloxy radical to a pseudo-Photo-Kolbe process involving the formation of resonance-stabilized zwitterion radicals as intermediates.

N-(4-Methoxybenzyl)phthalimide: a triclinic polymorph

“…For a photochemical study of the title compound, see: Warzecha, Gö rner et al (2006). For related compounds, see: Lü et al (2006); Warzecha et al (2006a); Chen et al (2006).…”

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Key indicators: single-crystal X-ray study; T = 100 K; mean (C-C) = 0.002 Å; R factor = 0.034; wR factor = 0.087; data-to-parameter ratio = 13.9.The title compound [systematic name: 2-(4-methoxybenzyl)-isoindoline-1,3-dione], C 16 H 13 NO 3 , represents a triclinic polymorph of the previously reported monoclinic form [Warzecha et al (2006). Acta Cryst.

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“…The title compound [systematic name: 2-(4-methoxybenzyl)-isoindoline-1,3-dione], C 16 H 13 NO 3 , represents a triclinic polymorph of the previously reported monoclinic form [Warzecha et al (2006). Acta Cryst.…”

Synthesis of 3‐Benzylated Isoindolinones by Photoredox Decarboxylation of Arylacetates in the Presence of N‐Benzylphthalimide: Conductivity as a Kinetic Tool

“…In recent years, we and others have intensively investigated the non‐catalytic intermolecular photoaddition of alkyl carboxylates to phthalimides . The mechanistic details were elucidated for the chromophore component (triplet state and radical anion detection) by static and time‐resolved spectroscopic methods . These intermolecular photoinduced electron transfer reactions lead to an interesting class of products, 3‐hydroxyisoindolinones, that can be further dehydrated to 3‐methylene derivatives or deoxygenated to biologically relevant isoindolinones .…”

Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan

“…N-Alkylated phthalimides typically absorb in the 295 nm region with extinction coefficients around 10 3 . The quantum yields for intersystem crossing Ф ISC significantly change with the substitution on the imide nitrogen, e.g., Ф ISC = 0.5 for N -isobutylphthalimide and Ф ISC < 0.01 for N -arylphthalimides [1]. If necessary, the population of the triplet state is also possible by sensitization, e.g., with triplet sensitizers such as acetone or benzophenone.…”