Four-Component Cyclization of Naphthol/Thionaphthol/Naphthylamine, Formaldehyde, and DBU in Water

Abstract

A practical and environmentally benign cascade multicomponent condensation of naphthol/thionaphthol/naphthylamine, formaldehyde, and DBU in water without any catalysts has been achieved. A wide variety of dihydrooxazine, dihydrothiazine, and tetrahydrobenzoquinazoline derivatives N-substituted with a tether bearing a caprolactam unit were afforded in moderate to good yields. The advantages of being cost-effective, metal-free, and easily handled and the use of water as medium made this protocol conform with the principle of green synthesis.

Isothiocyanates (in situ) and sulfonyl chlorides in water for N-functionalization of bicyclic amidines: access to N-alkylated γ-/ω-lactam derivatized thiourea and sulfonamides

“…1,2 Recently, there has been a notable increase in the utilization of DBU and DBN as nucleophiles, as evidenced by the growing number of publications in this area. 3 These compounds have shown their nucleophilic potential through diverse synthetic pathways encompassing Michael-type additions, carbonyl addition, CC and CC bond addition, halide or acetate substitution, arene substitution, and N -arylation. 1–3 Overall, the versatility of DBN and DBU makes them valuable tools in synthetic organic chemistry, both as non-nucleophilic bases and catalysts and as emerging nucleophiles.…”

Construction of Diverse N-Heterocycles by Formal (3 + 3) Cycloaddition of Naphthol/Thionaphthol/Naphthylamine and 1,3,5-Triazinanes

“…Dihydrooxazine, dihydrothiazine, and tetrahydrobenzoquinazoline N -heterocyclic molecules are widely used in many pharmaceuticals and bioactive molecules due to their important biological activities, such as anti-tumor, anti-bacterial, and anti-HIV. − Therefore, the development of efficient protocols to construct these nitrogen-containing heterocyclic structural units is one of the most notable subjects . Continuing our interest in the synthesis of nitrogen-containing heterocycles, herein, we turned our attention to building dihydrooxazine, dihydrothiazine, and tetrahydrobenzoquinazoline derivatives via metal-free formal (3 + 3) cyclization of naphthol/thionaphthol/naphthylamine using 1,3,5-triazinanes as efficient three-atom synthons (C–N–C) (Scheme c).…”

Ferrocene-Mediated Photocatalytic Annulation of N-Sulfonyl Ketimines on a Polycrystalline WSe2 Semiconductor Photocatalyst

“…In view of the importance of iminium ion intermediates in the above-reported photocatalytic reactions, we envisioned that the low-cost formaldehyde (HCHO) can be used as C1 synthon for the generation of iminium intermediate via the Mannich reaction. In continuation of our efforts on the photocatalysis, we herein report the ferrocene-mediated semiheterogeneous photocatalysis with polycrystalline WSe 2 (band gap: 1.75 eV) as a semiconductor photocatalyst and ferrocene as a redox catalyst.…”