Aqua-mediated one-pot synthesis of Biginelli dihydropyrimidinone/thiones (DHPMs), Hantzsch dihydropyridines (DHPs), and polysubstituted pyridines sonocatalyzed by metal-supported nanocatalysts

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.…”

“…Safa et al [120] promoted an aqua-mediated one-pot synthesis of Hantzsch DHPs sonocatalyzed by metal-supported nanocatalysts ( Table 2 , Entry 4). In this work they investigated under mild conditions some catalysts with different transition metals (Mn, Fe, Co, and Cu) and γ-alumina (γ-Al 2 O 3 ), Zeolite Socony Mobil-5 (ZSM-5), as an aluminosilicate zeolite, and silicoaluminophosphate molecular sieve (SAPO-34) and different solvents at room temperature such as ethanol, ethanol/water, acetonitrile, acetonitrile/water, water, DCM, toluene and solvent-free (120 °C).…”

“… Entry Catalyst Conditions a Examples Yields (%) Ref. 1 NDL 5 EtOH:H 2 O, 30–45 min, 45–50 °C 13 c 82-97 d [131] 2 Polindole s.f b , 20–37 min, 45 °C 18 90–97 [132] 3 SBA-15/SO 3 H 25 min, r.t. 17 88–97 [121] 4 Fe–Cu/ZSM-5 H 2 O, 5 min, r.t. 9 e 92-97 f [120] 5 Dendrimer-PWA 5–15 min, 50 °C 18 88–97 [133] *Ultrasonication parameters: Entry 1. Ultrasonic bath with built-in heating, 45–50 °C; frequency: 35 kHz; power: 160/640 W. Entry 2. frequency: 33 kHz; power: 100 W, further details were not provided.…”

Similarity and Competition between Biginelli and Hantzsch Reactions: an Opportunity for Modern Medicinal Chemistry

“…Lewis acids embedded into metal-organic frameworks (MOF) [92] or into zeolites [93] have also been tested to synthesize classical 1,4-DHPs and DHPMs (entries 9, 10 Table 1), respectively under solvent-free conditions and in water. In the first case, a IRMOF [Zn 4 O(H 2 N-TA) 3 -Zn derivative of 2-aminoterephthalic acid] heterogeneous catalyst was synthesized, characterized and tested, thus confirming the compatibility with both reactions, even under heating.…”

“…[92] In the second case, the Cu-Fe/ZSM-5 (Zeolite Socony Mobil-5) catalyst gave rise to good results in both reactions, which is quite surprising as water, under acidic conditions, can hydrolyze urea. [93] It becomes evident that hydrolysis does not happen under room temperature conditions, thus opening the possibility of using water compatible Lewis acids in in both MCRs.…”