Synergistic catalytic effect between ultrasound waves and pyrimidine-2,4-diamine-functionalized magnetic nanoparticles: Applied for synthesis of 1,4-dihydropyridine pharmaceutical derivatives
Authors: Jamal Rahimi
Ali Maleki
Reza Taheri-Ledari
Journal: Ultrasonics sonochemistry (2019)
Discipline: CHEMISTRY
Keywords: Dihydropyridine; Heterogeneous catalyst; Iron oxide nanoparticles; Multicomponent reaction; Sonochemistry.
Affiliations: Catalysts and Organic Synthesis Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114, Iran., Catalysts and Organic Synthesis Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114, Iran. Electronic address: .

Abstract:  A convenient strategy for synthesis of the various derivatives of 1,4-dihydropyridine (1,4-DHP), as one of the most important pharmaceutical compounds, is presented in this study. For this purpose, firstly, magnetic iron oxide nanoparticles (Fe3O4 NPs) were fabricated and suitably coated by silica network (SiO2) and trimethoxy vinylsilane (TMVS). Then, their surfaces were well functionalized with pyrimidine-2,4-diamine (PDA) as the main active sites for catalyzing the synthesis reactions. In this regard, the performance of three different methods including reflux, microwave (MW) and ultrasound wave (USW) irradiations have been comparatively monitored via studying various analyses on the fabricated nanocatalyst (Fe3O4/SiO2-PDA). Concisely, high efficiency of the USW irradiation (in an ultrasound cleaning bath with a frequency of 50 kHz and power of 250 W/L) has been well proven through the investigation of the main factors such as excellent surface-functionalization, core/shell structure conservation, particle uniformity, close size distribution of the particles, and great inhibition of the particle aggregation. Then, the effectiveness of the USW irradiation as a promising co-catalyst agent has been clearly demonstrated in the 1,4-DHP synthesis reactions. It has been concluded that the USW could provide more appropriate conditions for activation of the catalytic sites of Fe3O4/SiO2-PDA NPs. However, high reaction yields (89%) have been obtained in the short reaction times (10 min) due to the substantial synergistic effect between the presented nanocatalyst and USW. 

Retracted: No

PubPeer comments:
 * Pink boxes: Figure 4C of this paper appears to show an overlap with Figure 4A from another paper by the same group, i.e. Ali Maleki et al. ACS Omega 2019, 4, 10629u221210639, DOI: 10.1021 acsomega.9b00986 - https: pubpeer.com publications 0573933A1A9A521446BA949BF6A5F3 The photos appear to be showing different nanocomposites: * Ali Maleki 2019 10.1021 acsomega.9b00986: Fe3O4@SiO2@vinyl * Reza Taheri-Ledari 2019, 10.1016 j.ultsonch.2019.104737: Fe2O4 SiO2.PDA USW Irradiation Could the authors please clarify if these were the same samples?  , 
 * Green boxes: Figure 4B of this paper appears to show an overlap with Figure 3d from another paper by the same group, i.e. Reza Taheri-Ledari et al., Ultrasonics - Sonochemistry 61 (2020) 104824, DOI: 10.1016 j.ultsonch.2019.104824 - https: pubpeer.com publications F3599129F50A4D5E02210588FE9C7C The photos appear to be showing different nanocomposites: * Figure 3d from Reza Taheri-Ledari 2020, 10.1016 j.ultsonch.2019.104824: Fe3O4@Pd CaCO3-DTT NPs reflux method * Figure 4b from Reza Taheri-Ledari 2019, 10.1016 j.ultsonch.2019.104737: Fe3O4@PDA NPs MW irradiation. Could the authors please clarify if these were the same samples?  , 
 Added to comments in #1 and #2, Figure 4-c. of this paper (DOI: 10.1016 j.ultsonch.2019.104737) is disturbingly similar to Figure 6-A in this paper (DOI: 10.1002 slct.201803001) and Figure 4-(a), SEM images of Fe3O4@SiO2@vinyl MNPs in this paper (DOI:10.1021 acsomega.9b00986). ***  *** ,