Synthesis of 1,4‐Dicarbonyl Compounds by Visible‐Light‐Mediated Cross‐Coupling Reactions of α‐Chlorocarbonyls and Enol Acetates

Abstract

Herein, we report a protocol for visiblelight-mediated radical coupling reactions of αchloroketones and enol acetates to afford 1,4dicarbonyl compounds, which are important precursors and intermediates in organic synthesis. The reaction involves photoredox-catalyzed activation of the α-chloroketone upon photoelectron transfer, carbon-chlorine bond cleavage, and coupling of the resulting radical with the carbon-carbon double bond of the enol acetate. This mild protocol has a wide substrate scope and moderate to good yields.

Recent Developments on Photochemical Synthesis of 1,n‐Dicarbonyls

“…Inspired by the active participation of the α-bromo ketones in the photochemical synthesis of 1,4-dicarbonyls, Song and Wang developed a process for synthesizing 1,4-dicarbonyl compounds upon photoexcitation on α-choloroketone 57 and enol acetate 54 in the presence of fac-Ir(ppy) 3 photocatalyst (Scheme 42). [78] The plausible mechanism is similar to that of Scheme 41, where the alkyl radical A couples with enol acetate 54 to form the corresponding radical B which upon oxidation followed by hydrolysis affords the desired 1,4-dicarbonyl compounds 58. This method includes several α-chloro carbonyls and phenyl vinyl acetates to produce a series of 1,4dicarbonyls in moderate to good yields.…”

Primary and Secondary Amines by Flavin‐Photocatalyzed Consecutive Desulfonylation and Dealkylation of Sulfonamides

“…[29] The same protocol was used for arenesulfonamides, but its application is limited by the use of high temperature and UV light. [30] A few reductive photodesulfonylation methods based on visible light photoredox catalysis have also been described; [31][32][33][34][35][36][37][38][39] recently, Budén, [40] Nicewicz, [41] Kang [42] and Hasegawa [43] published photodetosylation using an excited Hantzsch ester anion, an acridinium salt, diphenyldibenzocarbazole or triarylamine-substituted benzimidazolium, respectively (see example in Scheme 1B). However, all these photochemical methodologies suffer from limited substrate scope from the point of view of sulfonyl group structure and are limited to tosyl derivatives.…”

Titanium-Mediated Domino Cross-Coupling/Cyclodehydration and Aldol-Addition/Cyclocondensation: Concise and Regioselective Synthesis of Polysubstituted and Fused Furans

“…The Feist–Bénary reaction can be viewed as a base-catalyzed aldol-alkylation reaction and generally produces furans with a 3-acyl group . To obtain other substituted furans derived from ketones and α-haloketones, multistep reactions are often required (Scheme , Route b) . Ketones can be first transformed into their corresponding stabilized enolate, and then coupled with α-haloketones to afford 1,4-diketones, followed by dehydration to produce various substituted furans .…”