Green synthesis of benzimidazoloquinazolines and 1,4-dihydropyridines using magnetic cyanoguanidine-modified chitosan as an efficient heterogeneous nanocatalyst under various conditions

Greener organic synthetic methods: Sonochemistry and heterogeneous catalysis promoted multicomponent reactions

“… Entry Catalyst Conditions a Examples Yields (%) Ref. 1 SBA-15/SO 3 H Solvent-free, 8 min, 100 °C 5 80–86 [121] 2 Fe 3 O 4 @GA@IG 35–70 min 12 77–92 [118] 3 MCGC b 10–66 min, 40–42 °C 8 90–96 [119] 4 Cu-Fe/ZSM-5 H 2 O, 5 min 6 93–99 [120] *Ultrasound parameters: Entry 1. Ultrasound device equipped with a converter/transducer and titanium oscillator (horn),12.5 mm in diameter; frequency: 19.6 kHz; power: 600 W. Entry 2.…”

“…Stimulated by the interest in investigating the usefulness of biopolymers as an efficient support in nanocatalysis, Javanmiri et al [119] have combined the qualities of chitosan - non-toxicity, biodegradability, biocompatibility - with the properties of magnetically modified cyanoguanidine (MCGC) to obtain a highly convenient heterogeneous nanocatalytic system, which has been successfully applied to the green synthesis of a series of 1,4-DHPs, in 0.5 w/w % loading, by using EtOH as a solvent ( Table 2 , Entry 3). The reaction was performed by using an ultrasonic cleaner bath at temperature of 40–42 °C, with a frequency of 25 kHz and the power was not informed.…”

“…The benzimidazoles are N -heterocycles with a wide spectrum of biological activities, such as anti-inflammatory and antitumor [176] . In the same work reported in section 2.1.1, Javanmiri et al [119] synthesized a series of benzimidazoloquinazolines ( 75 ), with some modifications in the method, via MCR of 2-aminobenzimidazole ( 76 ), aldehydes ( 1 ) and dimedone ( 4 ) ( Scheme 28 and Table 9 , Entry 1). The efficiency of this protocol was compared with some of the methods previously reported in literature for the synthesis of benzimidazoloquinazolines, showing advantages in terms of the catalyst loading, solvent, temperature, in addition to reaction time and yield.…”

“… Entry Catalyst Conditions Examples Yields (%) Ref. 1 MCGC EtOH, 10–66 min, 40–42 °C 8 84–91 [119] 2 s/Fe 3 O4/MNPs H 2 O, 3–9 min, r.t. 5 95–98 [177] *Ultrasonication parameters: Entry 1. Ultrasound bath at temperature of 30°-32 °C; frequency: 25 kHz, further details were not provided.…”

Recent developments in the nanomaterial-catalyzed green synthesis of structurally diverse 1,4-dihydropyridines

“…The usefulness of this method lies in its benets such as short reaction times, low catalyst loading, milder reaction conditions, easy work-up procedure, compatibility with varied range of substituted aromatic aldehydes, and reusability up to eight consecutive cycles. 92 Magnetic nanoparticles with N-propylbenzoguanamine sulfonic acid immobilized on silica-coated nano-Fe 3 O 4 particles (MNPs-NPBG-SA), as a novel and effective catalyst with good recyclability and reusability, was synthesized (Scheme 11) and utilized in the preparation of 1,4-dihydropyridine derivatives.…”