1,3-(4,4'-dipyridinium disulfonic acid)propane dimethanesulfonate as an effective double-functional catalyst in preparing N,N′-Methylene bisamides, Tetrahydrochromeno-chromenes, and Pyrido-dipyrimidines

In this paper, a dual-functional Brønsted acidic ionic liquid (BAIL) catalyst, namely 1,3-(4,4'-dipyridinium disulfonic acid)propane dimethanesulfonate (DPDSPDM), was produced, and its structure was identified using TGA, FT-IR, ¹³C NMR, ¹H NMR, and mass spectrometry techniques. Then, it was utilized as a versatile, homogeneous, and recyclable catalyst in preparing N,N'-Methylene bisamides (1a-14a, 5–13 min, 90–98%, 50 °C, solvent-free), Tetrahydrochromeno-chromenes (1b-12b, 8–20 min, 91–98%, 60 °C, solvent-free), and Pyrido-dipyrimidines (1c-12c, 2–5 min, 93–98%, 25 °C, H₂O). In all three synthetic routes, the catalytic activity scope of DPDSPDM was remarkable and general due to having basic (MeSO₃ˉ) and acidic (SO₃H) sites, and reasonable mechanisms were displayed to support this high performance. The reproducibility of this homogeneous catalyst along with advantages such as appropriate TOF (turnover frequency) and TON (turnover number) values, mild conditions, simplicity of the workup, short reaction times, high yields, non-metallic nature of the catalyst, and the use of cheap and available raw materials in its synthesis; making it a potential candidate for future research. Graphical abstract: (Figure presented.)