Photoredox-Catalyzed Decarboxylative Alkylation of Silyl Enol Ethers To Synthesize Functionalized Aryl Alkyl Ketones

Abstract

Photoredox-catalyzed decarboxylative alkylation of silyl enol ethers has been developed. Diverse functionalized aryl alkyl ketones were afforded in modest to good yields using N-(acyloxy)phthalimide as an easy access alkyl radical source under mild and operationally simple conditions. The excellent performance of drug molecules such as fenbufen and indomethacin and naturally occurring carboxylic acids such as stearic acid and dehydrocholic acid further demonstrated the practicability of the reaction.

Catalyst‐free Decarboxylation and Decarboxylative Giese Additions of Alkyl Carboxylates through Photoactivation of Electron Donor‐Acceptor Complex

“…Indan-2carboxylic acid derived RAE was chosen as model substrate for easily tracing the product under thin layer chromatography. Maleate was also suitable substrate (8). Maleate was also suitable substrate (8).…”

“…N-vinyl carbazole was amenable substrate to deliver N-alkylated carbazole in moderate yield (15), while vinyl alkyl ether did not afford the desired addition product probably due to the competitive radical oligomerization of vinyl ether (16). Substituents on both αand β-positions were tolerated (7,8,18,20). Substituents on both αand β-positions were tolerated (7,8,18,20).…”

“…[3] Besides the atom-and step-economic methods to utilize carboxylic acids directly, [4] the traceless activation group strategy that uses N-(acyloxy)phthalimide (socalled redox active esters or RAEs), [5] which can be easily installed through condensation reaction, [5c] offered the other convenient way to perform various decarboxylative transformations. [6] The majority of the developed methodologies for decarboxylative carboncarbon bond formation utilized either transition-metal complexes as catalyst under thermal condition [7] or photoredox catalysts [8] to activate RAEs, especially for COMMUNICATIONS [a] Reaction condition: olefines (0.2 mmol), RAEs (0.3 mmol), HE (0.3 mmol) in DMA (2 mL), irradiated by 40 W blue LEDs (456 nm) at room temperature for 12 h under argon atmosphere. Yield of isolated product.…”

“…A broad scope of olefins exhibited as amenable substrates, including α,β-unsaturated ester (2)(3)(4)18), sulfone (5), nitrile (6), aldehyde (7), amide (9, 10), phosphate (11), and ketone (19). Maleate was also suitable substrate (8). The reaction also worked well with vinyl silane and vinyl pinacol boronate (12)(13)(14), albeit in moderate yields.…”

Alternate Energy Sources for Sustainable Organic Synthesis

“…Photoredox‐catalysed decarboxylative alkylation of silyl enol ethers using N ‐(acyloxy)phthalimides provides an example of photoredox‐catalysed ketone synthesis. The exceptional performance of drug molecules like indomethacin and fenbufen as well as that of the naturally occurring carboxylic acids such as stearic acid and dehydrocholic acid, renders this methodology immensely important (Scheme ) . The mechanism involves the reductive quenching of the photocatalyst by accepting one electron from the carboxylic acid followed by its oxidative quenching where it donates an electron to the N ‐(acyloxy)phthalimides.…”