Pyrimidopteridine N‐Oxide Organic Photoredox Catalysts: Characterization, Application and Non‐Covalent Interaction in Solid State

Abstract

Herein we report the photo‐ and electrochemical characterization of pyrimidopteridine N‐oxide‐based heterocycles. The potential of their application as organic photoredox catalysts is showcased in the photomediated contra‐thermodynamic E→Z isomerization of cinnamic acid derivatives and oxidative cyclization of 2‐phenyl benzoic acid to benzocoumarin using molecular oxygen as a mild oxidant. Furthermore, unprecedented intermolecular non‐covalent n–π‐hole interactions in solid state are discussed based on crystallographic and theoretical data.

Direct decarboxylative Giese reactions

“…Inspiration from flavin catalysis has led to the development of the structurally related pyrimidopteridine N -oxides (PPTNO). 95 Possessing high excited-state reduction potentials (* E red 1/2 ≈ +2.32 V) 95 b and good stability, these PCs have been investigated by Pospech and co-workers for use in direct DGRs (Scheme 39). 96 They employed catalyst tetrapropyl-pyrimidopteridine N -oxide ( PrPPTNO ), developing conditions that require low PC loadings, substoichiometric amounts of base, short reaction times, and low light intensity.…”

Photo-Mediated Decarboxylative Giese-Type Reaction Using Organic Pyrimidopteridine Photoredox Catalysts

“…Purification by column chromatography (n-pentane/EtOAc = 8:1) yielded the title compound 8pb (61 mg, 0.15 mmol, 30%) as a pale yellow oil (mixture of diastereomers). R f = 0.44 (n-pentane/EtOAc = 8:2, KMnO 4 ); 1 H NMR (300 MHz, CDCl 3 ) δ 7.26 (m, 2H), 7.15 (m, 3H), 4.51 (d, J = 9.4 Hz, 0.39H), 4.21 (m, 5.88H), 3.77 (m, 0.53H), 3.48 (d, J = 6.8 Hz, 0.52H), 3.34 (m, 0.48H), 2.99 (m, 0.53H), 2.76 (d, J = 6.7 Hz, 0.76H), 2.62 (m, 0.54H), 2.45 (m, 1.08H), 1.28 (m, 15.88H), 1.11 (m, 1.77H), 0.92 (t, J = 7.2 Hz, 1.41H); 13 (18), 288 (4), 262 (17), 216 (100), 198 (16), 170 (32), 142 (27), 131 (16), 124 (49), 96 (17), 91 (33), 69 (10), 57 (52); HRMS (ESI-TOF) m/z: [M + Na] + Calcd for C 13 H 24 O 4 Na 430.2205; Found 430.2217. IR (ATR, neat, cm −1 ): 2978 (w), 2936 (w), 1726 (w), 1700 (w), 1497 (w), 1455 (w), 1389 (w), 1366 (w), 1168 (w), 1028 (w), 700 (w).…”

“…32 In 2019, our group started to investigate these intriguing heterocycles with respect to their applicability as organic photoredox catalysts. 33 Yield determined by calibrated GC using biphenyl as an internal standard. Yield in parentheses represents isolated yield.…”

The Role of Solvent in Tautomer Solvate Crystallization: A Case of 6-Amino-1,3-Dimethyl-5-Nitrosouracil

“…6-Amino-1,3-dimethyl-5-nitrosouracil (NAU) is an intermediate of N-oxide organic photoredox catalysts [20] and caffeine [21]. A pair of NAU tautomeric forms ( Fig.…”