Knoevenagel condensation of 4,5- and 1,8-diazafluorenes

• Darya S. Cheshkina,
• Christina S. Becker,
• Alina A. Sonina and
• Maxim S. Kazantsev

Beilstein J. Org. Chem. 2026, 22, 803–812, doi:10.3762/bjoc.22.62

• with ketones resulted in unique di(pyridin-2-yl)methylene)-9H-diazafluorenes being electron-deficient ligands and functional materials. Keywords: acidic conditions; diazafluorene; diazafluorenylidene; Knoevenagel condensation; protonation; Introduction Diazafluorenylidene derivatives were reported to

• examples are scarce, especially for 1,8-diazafluorene. We have previously reported the condensation of 4,5-diazafluorene (1) with aromatic aldehydes and dialdehydes under ammonium acetate catalysis in acetic acid giving the corresponding products in good yields [5][23]. Remarkably, the only condensation of

• 1,8-diazafluorene (2) was performed using a TiCl4/pyridine system. However, the reaction yield was very low (11%) [15]. The latter approach was also used [22] for the condensation of 4,5-diazafluorene with ketones being especially challenging due to sterical issues. Moreover, this approach requires

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• . Regarding the materials developed by Lin et al., supramolecular coordination of PF8-co-DAF8 (13, Figure 5) with Lewis acids played an important role. They selected the more rigid 4,5-diazafluorene (DAF) with nitrogen atoms inserted at the 4 and 5-positons of the fluorene moiety [33]. The heteroatomic

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• -(diphenylphosphine)ethyl)-4,5-diazafluorene ligand 47 which includes a cyclopropylated intermediate (45, Scheme 8). The ligand was prepared by an initial cyclopropanation of diazafluorene 44. For this, 44 was treated with a dibromomethane solution in THF in the presence of sodium hydride under reflux for four hours