One-pot synthesis of 2-amino-3-cyanopyridines and hexahydroquinolines using eggshell-based nano-magnetic solid acid catalyst via anomeric-based oxidation

Waste-to-wealth transition: application of natural waste materials as sustainable catalysts in multicomponent reactions

“…According to the elemental analysis of S, ∼5.875 mmol g −1 of SO 4 H group was loaded on the Fe 3 O 4 @eggshell, while back titration suggested that ∼5.18 mmol SO 4 H group was placed per gram of the Fe 3 O 4 @eggshell. 60…”

“…Fe 3 O 4 was functionalized with eggshell as an inexpensive material, adhering to the waste-to-wealth theme. 60…”

Magnetically recoverable catalysts for the preparation of pyridine derivatives: an overview

“…In this process, CaCO 3 from the eggshell was converted to Ca(HSO 4 ) 2 through reaction with ClSO 3 H ( Scheme 27 ). 54 …”

“…Nano-Fe 3 O 4 @Ca(HSO 4 ) 2 76 was subsequently utilised in the synthesis of 2-amino-3-cyanopyridines 23 via four-component reaction of different benzaldehydes 9, acetophenone 22, ammonium acetate 10, and malononitrile 16 under solvent-free conditions at 90 °C for 5–15 min ( Scheme 28 ). 54 …”

A green and novel method for the preparation of α-aminophosphonates using eggshell as catalyst. X-ray study

“…[17] Akbarpoor et al used nano-Fe 3 O 4 @ 1542 T.13 (HSO 4 ) 2 in the synthesis of hexahydroquinolines and 2-amino-3-cyanopyridines derivatives. [18] Madhukar B. Morbale et al describe the synthesis of 1,4-dihydropyridine and polyhydroquinoline; the preparation was carried out by the condensation of dimedone, aldehydes, ethylacetoacetate and ammonium acetate using modified eggshells (MES) as base catalyst. [19] In this particular context and in our continued research to develop novel, rapid and green approaches in the design of efficient synthetic methods using recyclable catalysts, we describe here the use of eggshell as an efficient biodegradable and recyclable heterogeneous catalyst for the preparation of aminophosphonates by a three-component condensation reaction in one pot.…”