Metal‐Free Carbonylations by Photoredox Catalysis

Abstract

The synthesis of benzoates from aryl electrophiles and carbon monoxide is a prime example of a transition-metal-catalyzed carbonylation reaction which is widely applied in research and industrial processes. Such reactions proceed in the presence of Pd or Ni catalysts, suitable ligands, and stoichiometric bases. We have developed an alternative procedure that is free of any metal, ligand, and base. The method involves a redox reaction driven by visible light and catalyzed by eosin Y which affords alkyl benzoates from arene diazonium salts, carbon monoxide, and alcohols under mild conditions. Tertiary esters can also be prepared in high yields. DFT calculations and radical trapping experiments support a catalytic photoredox pathway without the requirement for sacrificial redox partners.

Conjugated Microporous Poly(Benzochalcogenadiazole)s for Photocatalytic Oxidative Coupling of Amines under Visible Light

“…B-BO exhibited aV Ba nd CB at + 1.48 and À1.22 Vv ersus SCE, respectively.I nc omparison, the VB and CB positions of B-BT are slightly lower at 1.68 and À1.08 V, respectively.B -BS presented the narrowest band gap with the VB and CB at 1.35 and À1.06 Vv ersus SCE,r espectively.I ti s noteworthy that these valuesa re comparable to the redox potentials of well-established organometallic photocatalystss uch as [Ru(bpy) 3 ] 3 + (+ 1.29 Vv s. SCE, bpy = 2,2'-bipyridine) and [Ru(bpy) 3 ] 2 + (À0.81 Vv s. SCE), [30] whichs uggests promising photocatalytic capabilities of the conjugated polymers. The electron paramagnetic resonance (EPR)s pectra showedt he largesti ncreasei ns ignal intensity for B-BT under light irradiation compared to in the dark.…”

Organic Photoredox Catalysis

“…Concurrent reports from Jacobi von Wangelin 500 A similar carbonylation reaction of aryldiazonium salts 161.1 using CO and an arene or heteroarene nucleophile 161.2 was reported using eosin Y as a photoredox catalyst (Scheme 161). 502 The diarylketone products 161.3 could be achieved in good yields with simple arenes (161.4) and heteroarenes (161.5 and 161.6) and were proposed to form by a similar mechanism to the one shown in Scheme 160.…”

Merging Photoredox and Nickel Catalysis: The Direct Synthesis of Ketones by the Decarboxylative Arylation of α‐Oxo Acids

“…As a key design element, this photoredox approach to nickel-acyl complex formation would allow facile generation of a series of carbonyl products using mild conditions (room temperature), and without the need for toxic reagents or stoichiometric oxidants. [13] …”