Fe3O4@SiO2-BenzIm-Fc[Cl]/ZnCl2: a novel and efficient nano-catalyst for the one-pot three-component synthesis of pyran annulated bis-heterocyclic scaffolds under ultrasound irradiation

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

“…The synthesis of pyran[3,2- b ]pyran derivatives ( 1 2 2 ) under ultrasound irradiation was explored by a one-pot condensation reaction of aromatic aldehyde ( 1 ), malononitrile ( 9 ) and kojic acid ( 1 2 1 ) ( Scheme 41 ). In this context, the Nazari group [208] investigated the synthesis of bis-heterocyclic annulled derivatives via MCR using ultrasound irradiation. The reactions were carried out using a multiwave ultrasonic generator equipped with a converter / transducer and titanium oscillator (horn), 12.5 mm in diameter, operating at 20 kHz with a maximum 10–60 W output power.…”

“… Entry Catalyst Conditions a Examples Yields (%) Ref. 1 Fe 3 O 4 @SiO 2 -BenzIm-Fc[Cl]/ZnCl 2 8–12 min, r.t 10 86–98 [208] 2 SiO 2 @Imd-Cl@Fc 15–20 min, 25 °C 15 84–95 [209] *Ultrasound parameters: Entry 1. The ultrasonic irradiations were obtained by a multiwave ultrasound equipped with a converter/transducer and a titanium oscillator (horn), 12.5 mm in diameter, operating at 20 kHz with a maximum output power of 10–60 W. Entry 2.…”

“…The Nazari group, in a work already mentioned in this review [208] , evaluated the obtaining of pyran[3,2- d ]pyrimidines ( 1 2 3 ) via ultrasound-assisted cyclocondensation of aromatic aldehydes ( 1 ), malononitrile ( 9 ) and barbituric acid ( 1 1 1 ) using a functionalized recyclable magnetic nanoparticles (Fe 2 O 4 @SiO 2 -BenzIm-Fc[Cl]/ZnCl 2 ) ( Scheme 42 ). This protocol made possible to obtain 10 examples of pyran[3,2- d ]pyrimidines, with yields greater than 87%, with a reaction time between 10 and 15 min at room temperature.…”

“…Cyclocondensation reactions have also been explored to obtain pyran[3,2- c ]chromenes ( 1 2 4 ) by means of a multicomponent reaction using aromatic aldehydes ( 1 ), malononitrile ( 9 ) and 4-hydroxycoumarin ( 1 0 1 ) ( Scheme 43 ). In the work of the Nazari group [208] , already discussed in this review, pyran[3,2- c ]chromenes ( 1 2 4 ) were obtained with the use of magnetic nanoparticles coated with functionalized recyclable silica ( Table 14 , Entry 1). The method was carried out at room temperature and the solvent was a mixture of EtOH:H 2 O, with a short reaction time (10–20 min), under ultrasound irradiation operating at 20 kHz with a maximum 10–60 W output power.…”

“… Entry Catalyst Conditions Examples Yields (%) Ref. 1 Fe 3 O 4 @SiO 2 -BenzIm-Fc[Cl]/ZnCl 2 EtOH:H 2 O, 10–20 min, r.t. 12 85–96 [208] 2 Fe 3 O 4 @SiO 2 -BenzIm-Fc[Cl]/NiCl 2 15–20 min, 25 °C 9 87–95 [202] 3 Fe 3 O 4 @SiO 2 -Imid-PMA n H 2 O, 5–12 min, r.t 23 88–97 [203] *Ultrasound parameters: Entries 1 and 2. Reactions were carried out using a multiple wave ultrasonic generator equipped with a converter / titanium transducer and oscillator (horn), 12.5 mm in diameter, operating at 20 kHz with a maximum power output of 10–60 W and the power levels have been adjusted automatically.…”