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Green Chemistry and Green Catalysts
Published in Ahindra Nag, Greener Synthesis of Organic Compounds, Drugs and Natural Products, 2022
Ahindra Nag, Himadri Sekhar Maity
In conclusion, a simple, eco-friendly and novel procedure was demonstrated for the synthesis of bisenols and 2-amino-4H-pyrans using natural feedstock coconut juice. The major importance of using ACC juice is higher yields, no work-up and no column chromatography.
Hydrolytic Enzymes for the Synthesis of Pharmaceuticals
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Sergio González-Granda, Vicente Gotor-Fernández
In the previous section, the action of water as nucleophile in hydrolytic reactions of different organic compounds have been illustrated, here the role of other nucleophiles will be deeply analysed. For instance, the esterification of carboxylic acids with alcohols is well known, and this has allowed the formation of esters in non-selective and selective fashions. For instance, the reaction of substituted benzoic acids with alcohols and (N,N)-disubstituted amino alcohols has allowed the synthesis of interesting alkyl esters, some of them key intermediates in the synthesis of benzocaine, chloroprocaine and procaine anaesthetics (Giunta et al., 2013). The reaction with CAL-B and equimolecular amounts of a determined (amino) alcohol led to complete conversions in many cases by using cyclohexane as solvent, yielding the desired esters in quantitative yields after a simple work-up by filtration and solvent distillation (Scheme 9.19). Esterification of benzoic acids with alcohols in the presence of CAL-B.
Constitution of a Chemical Reaction and Reaction Balancing
Published in John Andraos, Reaction Green Metrics, 2018
A substance or material used in the post-processing of a chemical reaction typically in work-up procedures involving washing or extraction and in purification procedures involving chromatography or recrystallization.
An insight on the different synthetic routes for the facile synthesis of O/S-donor carbamide/thiocarbamide analogs and their miscellaneous pharmacodynamic applications
Published in Journal of Sulfur Chemistry, 2023
Faiza Asghar, Bushra Shakoor, Babar Murtaza, Ian S. Butler
The experimental conditions were first optimized using tetramethylguanidine and 1-isothiocyanato-4-nitrobenzene as models for producing the title compounds. In THF solvent, the model reaction was carried out with various base catalysts, Et3N, dimethylpiperazine, and catalyst-free conditions. In THF solvent, there was no significant yield difference in the presence of a base catalyst or in the absence of a catalyst. As a result, the condition without the catalyst was favored. The model reaction was carried out in a variety of organic solvents, such as THF, chloroform, dichloromethane, and acetonitrile, as well as in solvent-free and catalyst-free conditions. In contrast to reactions in the presence of solvents, simple mixing of 4-nitrophenylisothiocyanate and 1,1,3,3-tetramethyl guanidine without solvent yielded high-purity N-di(dimethylamino) methylene-N′-(4-nitrophenyl) thiourea in high yield with a simple work-up procedure (filtration and recrystallization). Later, the optimized solvent-free conditions were evaluated at various temperatures, including 40°C, 50°C, and 60°C, with the reaction proving to be effective at 60°C [61–63].
Efficient eco-friendly syntheses of dithiocarbazates and thiosemicarbazones
Published in Green Chemistry Letters and Reviews, 2020
Nur Halilatul Sadiqin O. Ali, Malai Haniti S. A. Hamid, Nurul Amirah ‘Aqilah Mohamad ‘Asri Putra, Hajar Azirah Adol, Aminul Huq Mirza, Anwar Usman, Tasneem A. Siddiquee, Md. Rejaul Hoq, Mohammad R. Karim
For the methodology that uses lemon juice (Citrus limonium) as catalyst, the Schiff bases were generally obtained at shorter reaction time (20–60 min) and generally higher yields (60–93%) as compared to the conventional method. Lemon juice is of the choice for catalyst because it is environmentally benign and is a green alternative to acid catalysts used in synthesis (27). The lemon juice obtained was filtered through a filter paper and the pH was recorded (pH = 2.3–2.5). The reaction was done at room temperature with stirring. A small amount of EtOH was added to ensure smooth stirring. Work-up was simply done by gravity filtration of the crude mixture, washing with cold EtOH, and followed by recrystallization from a suitable solvent. The Schiff bases synthesized by this method were obtained from moderate to excellent yields.
Efficient one-pot catalyst-free synthesis of novel coumarin- spiro[indoline-3,4'-pyran] conjugates via three-component domino reaction in aqueous medium
Published in Green Chemistry Letters and Reviews, 2019
Therefore, various catalysts such as L-proline, CTAB, DABCO, TEBA, BHDC were tested in the same condition of the model reaction. However, using these catalysts neither increased the yield of product nor shortened the reaction time significantly. The results were summarized in Table 1. Among them, 30 mol % amount of L-proline and 20 mol % amount of BHDC showed the highest yield (Table 1, entries 7 and 8).Afterwards, when the amount of BHDC was increased to 30 mol %, except the slight decreasing of yield, not any improvement was observed. Having optimized the reaction parameters, we generalized the applicability of this method for synthesis of a series of coumarin-spiro[indoline-3,4'-pyran] conjugates starting from various substituted coumarin β-ketoesters and isatins(Table 2). The work-up procedure of the reaction is very convenient, after completion the reaction(monitored by TLC), the product was isolated from the reaction mixture simply by filtration and pure target compounds were obtained in considerably high yields after further recrystallization.