Triphenylphosphine-catalyzed Alkylative Iododecarboxylation with Lithium Iodide under Visible Light

Abstract

Photoactivation of an electron donor–acceptor encounter complex in an organic solvent cage, a phenomenon that has been described in Mulliken theory, has been known for decades, but it has not been employed as a photoactivation step in the design of photocatalysis for organic synthesis until recent years. We report herein an iododecarboxylation reaction that applies this concept for photoactivation by using a catalyst to facilitate electron transfer and to suppress back electron transfer in the photoexcited state. Under irradiation of 456 nm blue light-emitting diodes, PPh3 catalyzes the iododecarboxylation of aliphatic carboxylic acid-derived N-(acyloxy)phthalimide with lithium iodide as iodine source. The reaction delivers primary, secondary, and bridgehead tertiary alkyl iodides in acetone solvent, and the alkyl iodide products were easily used to generate C–N, C–O, C–F, and C–S bonds to allow various decarboxylative transformations without using transition-metal or organic dye-based photocatalysts. This protocol is applicable to redox-active esters derived from various natural products and pharmaceuticals.

Triphenylphosphine-Catalyzed Alkylative Iododecarboxylation with Lithium Iodide under Visible Light

“…In summary, a PPh 3 -catalyzed iododecarboxylation protocol for use with aliphatic carboxylates and lithium iodide under irradiation with blue light has been developed . The reaction uses lithium iodide as the iodine source, proceeds under mild, redox-neutral conditions, and hence is suitable for modification of complex natural products and pharmaceuticals.…”

Design and Implementation of a Catalytic Electron Donor–Acceptor Complex Platform for Radical Trifluoromethylation and Alkylation

“…In 2019, Shang and Fu reported a strategy for EDA complex catalysis that utilized the combination of triphenylphosphine with sodium iodide as a catalyst species . Photoexcitation of the charge-transfer complexes formed from the triphenylphosphine/sodium iodide catalyst species with N -hydroxyphthalimide redox auxiliaries, Katritzky’s N -alkyl pyridinium salts, or Togni’s reagent promoted alkylation or trifluoromethylation reactions (Figure ).…”