Dicyanopyrazine-derived push–pull chromophores for highly efficient photoredox catalysis

Abstract

Here, we report dicyanopyrazine (DPZ)-derived push–pull chromophores, easily prepared and tunable organic compounds, as new kinds of photoredox catalysts.

Synthesis and properties of push-pull imidazole derivatives with application as photoredox catalysts

“…The starting imidazole-4,5-dicarbonitrile, 2-methoxythiophene, and thiophen-2-ylboronic acid (5) were commercially available. Compounds 1 25 and 4 32,37,38 were prepared according to literature. All cross-coupling reactions were carried out in flame-dried flasks under argon atmosphere.…”

“…DFT calculations. In contrast to DCP derivative 1, 25 ground state electrochemical properties (especially the first oxidation and reduction potentials) of DCI molecules 2 and 3 were out of the potential window of the employed electrochemical methods (cyclic voltammetry, rotating disc voltammetry or polarography). Hence, these fundamental properties were gained by DFT calculations.…”

“…The Suzuki-Miyaura reactions were carried out under optimized conditions involving [Pd2(dba)3] precatalyst, SPhos ligand, CsCO3 as a base, and THF/H2O (4:1) reaction media. 25 This reaction afforded 3 with diminished yield of 25% which was most likely caused by relatively low stability and possible catalytic system contamination by thiophene derivative 6.…”

“…24 Later on and upon structural tuning, a new DCP derivative 1 substituted with two 5-methoxythienyl donors was developed ( Figure 1). 25 Derivative 1 is a very efficient photoredox catalyst in various cross-dehydrogenative coupling (CDC) reactions 26 as well as in oxidation, oxidative hydroxylation, and reductive dehalogenation. 25 Further catalytic performance was demonstrated in chemodivergent radical cascade reactions between N-tetrahydroisoquinolines and N-itaconimides, 27 pH-controlled photooxygenation of indoles, 28 and enantioselective oxidative C(sp 3 )-H olefinations.…”

“…25 Derivative 1 is a very efficient photoredox catalyst in various cross-dehydrogenative coupling (CDC) reactions 26 as well as in oxidation, oxidative hydroxylation, and reductive dehalogenation. 25 Further catalytic performance was demonstrated in chemodivergent radical cascade reactions between N-tetrahydroisoquinolines and N-itaconimides, 27 pH-controlled photooxygenation of indoles, 28 and enantioselective oxidative C(sp 3 )-H olefinations. 29 In this work, we focus on synthesis of Yshaped push-pull analogues 2 and 3 based on five-membered acceptor unit -imidazole-4,5-dicarbonitrile (dicyanoimidazole, DCI) and further evaluation of their optoelectronic properties and photoredox catalytic activities.…”