Photoredox radical conjugate addition of dithiane-2-carboxylate promoted by an iridium(iii) phenyl-tetrazole complex: a formal radical methylation of Michael acceptors. Issue 2 (14th November 2016)

• Record Type: Journal Article
• Authors: Gualandi, Andrea; Matteucci, Elia; Monti, Filippo; Baschieri, Andrea; Armaroli, Nicola; Sambri, Letizia; Cozzi, Pier Giorgio
• Is Part Of: Chemical science. Volume 8:Issue 2(2017)
• Page Start: 1613
• Page End: 1620
• Publication Date: 2016-11-14
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c6sc03374a
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : An iridium(iii ) phenyl-tetrazole complex is a versatile catalyst for a new photocatalytic Michael reaction. Abstract : A readily accessible iridium(iii ) phenyl-tetrazole complex ([Ir(ptrz)2 ( t Bu-bpy)] +, 2 ; Hptrz = 2-methyl-5-phenyl-tetrazole; t Bu-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 of2, 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 photo-redox 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 catalyst2 allows selective formation of radicals only from α-heterosubstituted carboxylates. Chemical modification of this metal complex can tune the electrochemical properties, opening a route to new highly selective catalytic photo-oxidation reactions.