An Imine Photocyclization as an Alternative to the Pictet–Spengler Reaction for the Synthesis of AzaBenzannulated Perylenediimide Dyes

Abstract

AzaBenzannulated perylenediimide (AzaBPDI) dyes were synthesized in high yields via a new reaction sequence involving an imine condensation followed by visible light-induced photocyclization. The large scope and efficiency of this alternative to the Pictet–Spengler reaction are demonstrated, allowing easy preparation of dimeric AzaBPDI as potential non-fullerene acceptors for organic solar cells.

Visible-Light-Mediated Synthesis of AzaBenzannulated Perylenediimide-Based Light-Harvesting Dyads

“…Subsequent oxidation carried out by treatment with oxygen or DDQ gave dyads 7 (46% yield), 8 (35%), 9 (25%), and 10 (41%) in moderate yields (Scheme 1). All dyads were characterized by 1 H NMR, HRMS, and 13 C NMR in the case of compounds 7 and 8. The low solubility of 9 and 10 prevented the acquisition of satisfying 13 C spectra, even at high temperature in deuterated tetrachloroethane.…”

“…All dyads were characterized by 1 H NMR, HRMS, and 13 C NMR in the case of compounds 7 and 8. The low solubility of 9 and 10 prevented the acquisition of satisfying 13 C spectra, even at high temperature in deuterated tetrachloroethane. For evaluating their performance as NFAs in OSC devices, the cyclohexyl chains will be further replaced by swallow-tailed highly solubilizing substituents to ensure high processability and appropriate film morphology.…”

“…Resonance multiplicity was described as s (singlet), d (doublet), t (triplet), dd (doublet of doublets), m (multiplet), and br (broad signal). Carbon spectra were acquired with a complete proton decoupling 13 C{ 1 H}. MALDI-TOF spectra were performed on a Bruker Daltonics Biflex III using DCTB (trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile) as a matrix.…”

“…This methodology relies on a one-pot three-step sequence starting from (1) a condensation between 1-aminoPDI and an aldehyde (2) followed by the visible-light-promoted photocylization of the corresponding imine and (3) its subsequent oxidative rearomatization by DDQ. 13 With the aim of exploiting our procedure, we have been interested in synthesizing original AzaBPDI dyads by attaching electro-and photoactive electron-rich triphenylamine (TPA) or fluorene (Fl) species and electron-poor perylenediimide (PDI) or perylenemonoimide (PMI). We present herein the synthesis of those coreextended AzaBPDI derivatives, in addition to the electronic and photophysical properties of these light-harvesting dyads.…”

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“…Goujon, Hudhomme, and co-workers described the preparation of azabenzannulated PDI derivatives in a one-pot condensation–photocyclization–oxidation sequence from 1-aminoPDI 82.1 and various aryl aldehydes ( Scheme 82 ). 162 In the first step, an imine was formed from these starting materials in the presence of TFA. After concentrating the reaction mixture under vacuum, the crude imine was redissolved in DCM and subjected to visible-light irradiation, resulting in photocyclization to a secondary amine intermediate.…”