A readily accessible iridium(III) phenyl-tetrazole complex ([Ir(ptrz)(2)(tBu-bpy)](+), 2; Hptrz = 2-methyl-5-phenyl-tetrazole; tBu-bpy = 4,4'-di-tert-butyl-2,2'-bipyridine) is shown to be a versatile catalyst for a new photocatalytic Michael reaction. Under light irradiation in the presence of 2, a dithiane 2-carboxylic acid, obtained by simple hydrolysis of a commercially available ethyl ester, generates a 1,3-dithiane radical capable of performing addition to a variety of Michael acceptors (e.g., unsaturated ketones, esters, amides and malonates). This broad scope reaction with high yields is a formal photoredox addition of the elusive methyl radical and the adducts obtained can be starting materials for a variety of functionalized products. The excited-state oxidation potential of catalyst 2 allows selective formation of radicals only from alpha-heterosubstituted carboxylates. Chemical modification of this metal complex can tune the electrochemical properties, opening a route to new highly selective catalytic photo-oxidation reactions.

Photoredox radical conjugate addition of dithiane-2-carboxylate promoted by an iridium(III) phenyl-tetrazole complex: a formal radical methylation of Michael acceptors

Baschieri A.;
2017-01-01

Abstract

A readily accessible iridium(III) phenyl-tetrazole complex ([Ir(ptrz)(2)(tBu-bpy)](+), 2; Hptrz = 2-methyl-5-phenyl-tetrazole; tBu-bpy = 4,4'-di-tert-butyl-2,2'-bipyridine) is shown to be a versatile catalyst for a new photocatalytic Michael reaction. Under light irradiation in the presence of 2, a dithiane 2-carboxylic acid, obtained by simple hydrolysis of a commercially available ethyl ester, generates a 1,3-dithiane radical capable of performing addition to a variety of Michael acceptors (e.g., unsaturated ketones, esters, amides and malonates). This broad scope reaction with high yields is a formal photoredox addition of the elusive methyl radical and the adducts obtained can be starting materials for a variety of functionalized products. The excited-state oxidation potential of catalyst 2 allows selective formation of radicals only from alpha-heterosubstituted carboxylates. Chemical modification of this metal complex can tune the electrochemical properties, opening a route to new highly selective catalytic photo-oxidation reactions.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11697/139197
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