Photoiodocarboxylation of Activated C═C Double Bonds with CO₂ and Lithium Iodide

Abstract

The photolysis at 254 nm of lithium iodide and olefins 1 carrying an electron-withdrawing Z-substituent in CO2-saturated (1 bar) anhydrous acetonitrile at room temperature produces the atom efficient and transition metal-free photoiodocarboxylation of the CC double bond. The reaction proceeds well for terminal olefins 1 to form the new C–I and C–C σ-bonds at the α and β-positions of the Z-substituent, respectively, and is strongly inhibited by polar protic solvents or additives. The experimental results suggest that the reaction channels through the radical anion [CO2 •–] in acetonitrile, yet involves different intermediates in aqueous medium. The stabilizing ion-quadrupole and electron donor–acceptor interactions of CO2 with the iodide anion play a crucial role in the reaction course as they allow CO2 to penetrate the solvation shell of the anion in acetonitrile, but not in water. The reaction paths and the reactive intermediates involved under different conditions are discussed.

Zwitterion-Catalyzed Isomerization of Maleic to Fumaric Acid Diesters

“…Dimethyl fumarate ( 4b ): yield 35 mg (98%); white solid; eluent in chromatography, hexane/diethyl ether 20:1; 1 H NMR (CDCl 3 , 500 MHz) δ 6.85 (s, 2H), 3.79 (s, 6H); 13 C­{ 1 H} NMR (CDCl 3 , 125 MHz) δ 165.5, 133.5, 52.5. The physical data are the same as those in the literature …”

“…The physical data are the same as those in the literature. 30 Diethyl fumarate (4c): yield 43 mg (99%); white solid; eluent in chromatography, hexane/diethyl ether 20:1; 1 H NMR (CDCl 3 , 500 MHz) δ 6.84 (s, 2H), 4.25 (q, 4H, J = 7.1 Hz), 1.31 (t, 6H, J = 7.1 Hz); 13 C{ 1 H} NMR (CDCl 3 , 125 MHz) δ 165. 1, 133.8, 61.5, 14.2.…”

Light‐Mediated Carboxylation Using Carbon Dioxide

“…Iodide anion has strong absorption bands at UV region ( λ max =247.2 nm), being an ideal reagent for charge transfer to CO 2 . González‐Núñez and co‐workers uncovered a unique iodocarboxylation method of alkenes with UV light irradiation [14] . Lithium iodide is selected as the iodine source in this case.…”

Visible-Light-Driven Anti-Markovnikov Hydrocarboxylation of Acrylates and Styrenes with CO 2

“…[14][15][16][17][18][19][20][21][22][23] Hydrocarboxylations of alkenes with CO 2 , especially transition-metalcatalyzed hydrocarboxylations, represent efficient strategies to generate bioactive and synthetically useful carboxylic acids. 24 Recently, in addition to UV-light photocatalysis, 16,[25][26][27] visible-light photocatalysis has emerged as an intriguing strategy to realize novel organic transformations with CO 2 . 17,18,22,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] Notably, Iwasawa pioneered this strategy by realizing the hydrocarboxylation of alkenes with Markovnikov regioselectivity via visible-light photoredox/Rh dual catalysis.…”

“…17,18,22,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] Notably, Iwasawa pioneered this strategy by realizing the hydrocarboxylation of alkenes with Markovnikov regioselectivity via visible-light photoredox/Rh dual catalysis. 27,41 Besides Markovnikov selectivity, König et al 35 also realized a novel hydrocarboxylation of styrenes with anti-Markovnikov regioselectivity 26,[43][44][45] via photoredox/ nickel dual catalysis. In these cases, both photocatalysts and transition-metal catalysts are indispensable.…”