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Green Catalysis, Green Chemistry, and Organic Syntheses for Sustainable Development
Published in Miguel A. Esteso, Ana Cristina Faria Ribeiro, A. K. Haghi, Chemistry and Chemical Engineering for Sustainable Development, 2020
Divya Mathew, Benny Thomas, K. S. Devaky
The applicability of Strecker reaction relies on the synthesis of various α-aminonitriles, the precursors of α-amino acids. The substrates for Strecker reaction are ketones, aliphatic/aromatic amines, and trimethylsilyl cyanide. This reaction can be carried out in moderate to high yields and high purity using a new “green” Lewis acid catalyst, Nafion–Fe under conventional thermal, as well as microwave conditions. Iron Nafionate is Fe(III) salt of Nafion–H, a solid polymeric perfluoroalkanesulfonic acid. Simple reaction setup, easy work-up procedure, mild reaction conditions, shorter reaction times, and high purity of the products are the notable features of the methodology using Nafion–Fe. It is a reusable, environmentally benign, highly effective, and easily accessible catalyst. It has a significant contribution in green chemistry satisfying the emergent demand for environmentally benign and clean synthetic processes.19 Rare earth metal triflates and LASCs can function as easily recoverable and effectually reusable Lewis acids in aqueous media. Lewis acid catalysis can also be successfully carried out in scCO2 to contribute to the development of “greener” reactions.
Catalytic Asymmetric Michael Addition of Miscellaneous Carbon-centered Nucleophiles to Nitroalkenes
Published in Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera, Catalytic Asymmetric Reactions of Conjugated Nitroalkenes, 2020
Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera
In view of the aforementioned shortcomings, the use of preformed and structurally well-defined metal (salen) complexes allows a significant enhancement in the activity as exhibited by metal (salen) complexes in the enantioselective addition of trimethylsilyl cyanide 5 to nitroalkenes 1b. Loading of 2 mol% of catalyst afforded products 6a in good yields and excellent enantioselectivities at 0°C. According to the literature survey, complexes C9b are vanadium-based catalysts utilized in the present context, and the catalysts C9a are the titanium-based ones which were as active as that of vanadium-based catalysts. Three mole percent of the catalyst affords the products with moderate-to-good yields and enantioselectivities at 0°C (Scheme 6.11).12 In this reaction, the nitro group serves as a bidentate ligand and assists in bridging the two metal ions. Moreover, the stepped conformation of the silane ligand C9a/C9b allows the reaction of cyanide on the less hindered Si-face of the coordinated nitroalkene.
Name Reactions
Published in Benny K.G. Theng, Clay Mineral Catalysis of Organic Reactions, 2018
Yadav et al. (2004a) synthesized α-aminonitriles in 85%–94% yields by reacting aryl imines, formed in situ from aldehydes and amines, with trimethylsilyl cyanide (TMSCN) (3) in the presence of KSF montmorillonite. Scheme 5.26 shows an example of such a synthesis, using benzaldehyde (1) and aniline (2) as reactants, and yielding 2-anilino-2-phenylacetronitrile (4) as product. Sometime later, Wang et al. (2010, 2011a) reported that Sn-exchanged montmorillonite was similarly efficient in catalyzing the formation of α-aminonitriles by simply mixing a variety of aromatic and aliphatic carbonyl compounds (including sterically hindered ketones) with amines and TMSCN. The high activity of the catalyst was ascribed to its having strong Brønsted acid sites. These workers subsequently prepared nitriles by reacting various benzylic and allylic alcohols with trialkylsilyl cyanide in the presence of tin- and titanium-exchanged montmorillonites (Wang et al. 2011a).
Synthesis and characterization of Pd supported on methane diamine (propyl silane) functionalized Fe3O4 nanoparticles as a magnetic catalyst for synthesis of α-aminonitriles and 2-methoxy-2-phenylacetonitrile derivative via Strecker-type reaction under ambient and solvent-free conditions
Published in Inorganic and Nano-Metal Chemistry, 2021
Mingzhe Sun, Wei Liu, Wei Wu, Qun Li, Di Song, Li Yan, Majid Mohammadnia
They are greatly used as fundamental building blocks in peptide and protein synthesis, Traditionally, the Strecker reaction involves the nucleophilic addition of cyanide anion to imines.[27] α-Aminonitriles are commonly prepared by the nucleophilic addition of cyanide anion to imines using a diversity of cyanating agents such as HCN,[28] KCN,[29] K4[Fe(CN)6],[30] Et2AlCN,[31] and Me3SiCN,[29] under Strecker-type reaction conditions. Trimethylsilyl cyanide (TMSCN) is an effectual, easy of handling, and secure source of cyanide anions and is most prevalently used as a cyanide source in the presence of a variety of Lewis or Bronsted acid catalysts such as FeCl3,[32] NiCl2,[33] LiClO4,[34] SBA-15 supported sulfonic acid,[34] and sulfamic acid.[35] In other words, the majority of cyanide sources are perilous, toxic, involve coarse reaction conditions. Hence, TMSCN is the best alternative, because of the above-mentioned properties.[36]
Review: Recent advances of one-dimensional coordination polymers as catalysts
Published in Journal of Coordination Chemistry, 2018
Edward Loukopoulos, George E. Kostakis
CPs have also been employed as catalysts in the cyanosilylation of carbonyl compounds. The resulting cyanohydrins are versatile components in synthetic chemistry and act as intermediates in the preparation of compounds such as β-amino alcohols or α-hydroxy aldehydes. Trimethylsilyl cyanide (TMSCN) is the most commonly used cyanide source for formation of cyanohydrins [105, 106], however the use of a catalyst is also necessary in order to activate both the substrate and the cyanide precursor. A 1-D CP with relevant catalytic behavior was presented in 2016 by Pombeiro’s group [107]. The authors study the coordination capabilities of a rigid dicarboxylic acid ligand, 3,3′′-dipropoxy-[1,1′:4′,1′′-terphenyl]-4,4′′-dicarboxylic acid (H2dtda), with 3d elements such as Zn(II) and Cu(II). Out of the four reported compounds, the 1-D analog synthesized with Zn(II) nitrate was found to have the best catalytic performance in the aforementioned reaction. The compound, formulated as [Zn(dtda)(DMF)2] (29), features a zig-zag chain in which both oxygens of each carboxylate group of the ligand molecule coordinate to a Zn(II) center, while oxygens from DMF molecules occupy the axial positions of the resulting octahedra (Figure 27). 29 was then applied as a catalyst in a protocol that involved stirring of TMSCN and the aldehyde component in dichloromethane for 10 h at room temperature (Scheme 15). Remarkably, this procedure affords cyanohydrin derivatives with good to excellent yields (65–91%) and for a good range of aromatic and aliphatic substrates when only 2 mol% of 29 is used. In comparison, Zn(II) nitrate has poor catalytic behavior in the reaction, providing only 16% yield of the product. Furthermore, 29 may be reused for at least five cycles without loss in activity. The authors propose that the 1-D zig-zag architecture of 29 provides easy access to its Zn(II) sites, which could explain the high catalytic performance.