Gualandi Andrea, Matteucci Elia, Monti Filippo, Baschieri Andrea, Armaroli Nicola, Sambri Letizia, Cozzi Pier Giorgio
Dipartimento di Chimica "G. Ciamician" , ALMA MATER STUDIORUM Università di Bologna , Via Selmi 2 , 40126 Bologna , Italy . Email:
Dipartimento di Chimica Industriale "Toso Montanari" , ALMA MATER STUDIORUM Università di Bologna , Viale Risorgimento 4 , 40136 , Bologna , Italy . Email:
Chem Sci. 2017 Feb 1;8(2):1613-1620. doi: 10.1039/c6sc03374a. Epub 2016 Nov 3.
A readily accessible iridium(iii) phenyl-tetrazole complex ([Ir(ptrz)(Bu-bpy)], ; Hptrz = 2-methyl-5-phenyl-tetrazole; Bu-bpy = 4,4'-di--butyl-2,2'-bipyridine) is shown to be a versatile catalyst for a new photocatalytic Michael reaction. Under light irradiation in the presence of , 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 (, 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 catalyst 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.
一种易于获得的铱（III）苯基四唑配合物（[Ir(ptrz)(Bu-bpy)]；Hptrz = 2-甲基-5-苯基四唑；Bu-bpy = 4,4'-二叔丁基-2,2'-联吡啶）被证明是一种用于新型光催化迈克尔反应的通用催化剂。在光照下，在存在通过市售乙酯简单水解得到的二硫烷-2-羧酸的情况下，会产生能够与多种迈克尔受体（α,β-不饱和酮、酯、酰胺和丙二酸酯）进行加成反应的1,3-二硫烷基自由基。这种具有高收率的广泛反应是难以捉摸的甲基自由基的形式上的光氧化还原加成反应，并且所得到的加合物可以作为多种功能化产物的起始原料。催化剂的激发态氧化电位允许仅从α-杂取代羧酸盐选择性地形成自由基。这种金属配合物的化学修饰可以调节电化学性质，为新的高选择性催化光氧化反应开辟了一条途径。
