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Biocatalysis in Green Biosolvents
Published in Ahindra Nag, Greener Synthesis of Organic Compounds, Drugs and Natural Products, 2022
Margherita Miele, Laura Ielo, Vittorio Pace, Andrés R. Alcántara
These cyanohydrins are very useful building blocks for the ulterior synthesis of a plethora of pharmaceuticals and agrochemicals.215,216 The process depicted in Scheme 6.2 implies three consecutive steps and four catalytic reactions: an organocatalytic cyanosylilation of different aromatic aldehydes to furnish racemic O-sylilated α-aromatic acetonitriles (step-1), its transformation into the corresponding esters via two consecutive reactions (hydrolysis of the cyanosylil ether and subsequent acetylation, step-2) and, finally, enzymatic kinetic resolution of the racemic cyanohydrin ester by transesterification with propanol (step-3). The authors reported the optimization of each individual step under batch conditions, using SILLPs catalysts 1 and 2 shown in Scheme 6.2 for the initial steps (yields ranging from 95% to 99%); the enzymatic kinetic resolution was carried out using Novozym 435 and 2-MeTHF (yields from 52-57%, ee higher than 99% in all cases). The authors reported that the best SILLP catalyst for the second step was different from that used in the batch process; with this modification, they were able to obtain an excellent continuous process, leading to a noticeable space-time yield (STY) of 124 g g–1 cat h–1 L–1, comparable to that obtained with hydroxynitrileliases and HCN217 (a highly hazardous reagent), in a much greener manner.
List of Chemical Substances
Published in T.S.S. Dikshith, and Safety, 2016
Acetone cyanohydrin is extremely toxic. Exposures to acetone cyanohydrin cause adverse health effects. The symptoms of toxicity include, but are not limited to, irritation to the eyes, skin, respiratory system, dizziness, lassitude (weakness, exhaustion), headache, confusion, pulmonary edema, asphyxia convulsions, liver, kidney injury, pulmonary edema, and asphyxia. The target organs include the eyes, skin, respiratory system, central nervous system (CNS), cardiovascular system, liver, kidneys, and the gastrointestinal tract.
Synthesis and Production of Polylactic Acid (PLA)
Published in Jyotishkumar Parameswaranpillai, Suchart Siengchin, Nisa V. Salim, Jinu Jacob George, Aiswarya Poulose, Polylactic Acid-Based Nanocellulose and Cellulose Composites, 2022
Besides bacterial fermentation, lactic acid monomers are also prepared by the chemical synthesis method. Lactic acid can be prepared from acetaldehyde through a cyanohydrin reaction, as shown in Figure 2.2. The chemical synthesis follows two consecutive steps; first step is the formation of cyanohydrin and the second step is acidic hydrolysis. Industrially this process is favorable and is called the Sohio process. This process has only one demerit of adulteration by lactonitrile.
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.