Structure‐Catalytic Activity in a Series of Push‐Pull Dicyanopyrazine/Dicyanoimidazole Photoredox Catalysts

Abstract

A series of dicyanopyrazine and dicyanoimidazole derived push‐pull molecules have been prepared and further investigated as photoredox catalysts. The fundamental properties of the catalysts were studied by DSC, X‐ray analysis, absorption/emission spectra, and electrochemistry and were completed with the DFT results. The catalytic activity has been evaluated in visible light induced α‐functionalization of amines (cross‐dehydrogenative coupling and annulation reaction of tetrahydroisoquinolines). Thorough structure‐property‐catalytic activity relationships were elucidated. The developed series of tailored organic photoredox catalysts allows synthetic chemists to perform desired reactions under sustainable and mild conditions employing solely visible light as a source of energy.

Radical-based functionalization-oriented construction: rapid assembly of azaarene-substituted highly functionalized pyrroles

“…When using the strong Brønsted acids, i.e., TFA, TfOH and TsOH, no reaction was found (entry 10), which is most likely due to the generation of insoluble pyridinium salts from 1 with acids, thus hampering the reaction proceeding. Subsequently, a series of mixed solvents were evaluated (entries [11][12][13][14]; this evaluation was engaged in enhancing the solubility of NaH 2 PO 4 in the reaction system. To our delight, 9 was obtained in 93% yield when using mixed THF/CH 2 Cl 2 in a 1 : 1 ratio as the solvent system (entry 12).…”

“…With respect to the reactions of N-aryl glycines with 2-(2-enynyl)pyridine (2), products 9-16 were obtained in 79 to 96% yields. Electron-donating substituents on the N-aryl ring of glycines (10)(11)(12)(13) were benecial to chemoselectivity, presenting good to excellent yields. Moreover, although electron-withdrawing groups attenuated reactivity, introducing an extra electron-donating substituent could afford products 13 and 15 with equally satisfactory results.…”

A Rational Approach to Organo‐Photocatalysis: Novel Designs and Structure‐Property Relationships

“…This polarized system shows an effective CT character (Figure 19). In strong contrast to CDCB PCs, their weak fluorescence indicates a short S 1 lifetime (<1 ns) [41] . Hence, DPZ PCs exclusively react in their T 1 state.…”

“…In strong contrast to CDCB PCs,t heir weak fluorescence indicates as hort S 1 lifetime (< 1ns). [41] Hence,D PZ PCs exclusively react in their T 1 state.B ureš and co-workers suggested that this fast decay may be due to the heavy sulfur atom effect increasing the intersystem crossing rate from S 1 to T 1 .T wo structural features can be tuned to optimize the lifetime of the CT state of DPZ PCs: 1) the EDGs at positions 5a nd 6, and 2) the electron-withdrawing heterocyclic core,w ith the second possibility having an inferior impact.…”

“…The main strategy to modulate the reduction potential relies on modification of the donor groups [41] . The furyl group ( 79 a ) decreases the energy of the HOMO.…”