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Imidazolium Hydroxides and Catalysis
Published in Pedro Lozano, Sustainable Catalysis in Ionic Liquids, 2018
In an archetypal example of the furocoumarin synthesis (Scheme 4.17), 1-(cyanomethyl)pyridinium bromide was formed in situ from pyridine and bromoacetonitrile. The 4-hydroxycoumarin then underwent a Knoevenagel condensation with p-tolualdehyde followed by a Michael reaction with the pyridinium-ylide formed in situ by deprotonation of the pyridinium salt, and finally heterocyclization occurred from the nucleophilic attack of the ketone to yield the final furocoumarins. The use of [C4C1im][OH] gave excellent yields, whereas organic bases such as triethylamine and 1,8-Diazabicyclo(5.4.0)undec-7-ene (DBU) gave relatively poor yields. 2 mole equivalents of [C4C1im][OH] were used with yields decreasing with lower loading, so its role as a catalyst is not clear. The method of [C4C1im][OH] synthesis and halide content was not reported, so it is possible that the actual hydroxide loading was lower than the reported 2 mole equivalents.
Innovations in Noninvasive Instrumentation and Measurements
Published in Robert B. Northrop, Non-Invasive Instrumentation and Measurement in Medical Diagnosis, 2017
A patient at risk for blood clots is generally treated with the drug, warfarin (also known as Coumadin, Jantoven, Marevan, and Uniwarfin). Warfarin and related 4-hydroxycoumarin-containing compounds decrease blood coagulation by inhibiting the enzyme, vitamin K epoxide reductase, which leads to the reduction of vitamin K, necessary for the clotting process. (Vitamin K is found naturally in certain foods in two forms: K1 = phylloquinone and K2 = menaquinone.) Vitamin K2 is the main storage form in animals; it has several subtypes which depend on the isoprenoid “tail” chain length. Vitamin K1 is found mainly in green leafy vegetables, brassicas, grapes, etc. K2 is found in liver pâté, cheeses, chicken livers, egg yolks, etc. Because of unintentional, random dietary inputs of vitamin K, a person subject to embolism formation who is being treated with chronic warfarin may find his/her propensity to form clots variable in time. Because of this variability, patients being treated with warfarin are generally required to periodically monitor their clotting time as described by the international normalized ratio (INR), using a minimally invasive electronic instrument that uses a drop of blood on a proprietary test strip.
Microwave-Assisted Synthesis and Functionalization of Six-Membered Oxygen Heterocycles
Published in Banik Bimal Krishna, Bandyopadhyay Debasish, Advances in Microwave Chemistry, 2018
Neha Batra, Rahul Panwar, Ramendra Pratap, Mahendra Nath
Karanjule and coworkers generated trans 2,3-dihydro-furo[3,2-c]coumarins in high yields by using a highly efficient regioselective and diastereoselective protocol [148]. According to this protocol, 4-hydroxycoumarin reacted with substituted benzaldehydes and 2-bromo-1-phenylethanone in the presence of 4-(N,N-dimethylamino)pyridine (DMAP) as a base to afford the desired products in higher yields (Scheme 5.47).
A facile and practical p-toluenesulfonic acid catalyzed route to dicoumarols and their biological evaluation
Published in Green Chemistry Letters and Reviews, 2023
Sadeq M. Al-Hazmy, Donia Bensalah, Najet Aouled Dlala, Younes Bouazizi, Houcine Ghalla, Naceur Hamdi
The chemistry of coumarin derivatives has recently gained much attention from chemists owing to some interesting biological properties (13–15). Dicoumarols are a naturally occurring anticoagulant (16). The most popular strategies towards the synthesis of dicoumarols start from salicylaldehyde and formaldehyde and involve the biosynthesis of dicoumarols using micro-organisms such as Penicillium jenseni (17). The Knoevenagel condensation of 4-hydroxycoumarins with carbonyl compounds using several catalysts gives also dicoumarols (18–20). From an environmental and economic point of view, water as a solvent or media has many advantages and usually results in excellent efficiency and selectivity (21–23).
Investigation of catalytic, anti-bacterial, anti-oxidant, and DNA cleavage properties of bimetallic and trimetallic magnetic nanoalloys base on cupper
Published in Inorganic and Nano-Metal Chemistry, 2018
Kaveh Parvanak Boroujeni, Ahmad Farokhnia, Mansooreh Shahrokh, Mohsen Mobini
Heterocyclic systems are common structural motifs in many biologically active compounds and therefore intense effort has been devoted by researchers constantly to introduce newer and efficient protocols for their synthesis. Coumarin and its derivatives are a large group of heterocycles with a wide variety of biological and therapeutic properties such as anti-HIV,[19] cytotoxicity and enzyme inhibitory,[20] anti-fungal,[21] anti-bacterial,[22] anti-oxidant,[23] anti-cancer,[24] and anti-coagulant properties.[25] Among coumarin derivatives, biscoumarins become more popular and are usually prepared by the condensation reaction of aldehydes with 4-hydroxycoumarin. This reaction can be catalyzed by several types of catalysts such as piperidine,[26] I2,[27] sodium dodecyl sulfate,[28] [poly(4-vinylpyridine)BuSO3H]Cl.xAlCl3,[29] MW irradiation,[30,31] [poly(4-vinylpyridine)–BuSO3H]HSO4,[32] indion 190 resin,[33] choline hydroxide,[34] poly(AMPS-co-AA)@Fe3O4,[35] Zn(OAc)2,[36] and triethylammonium hydrogen sulfate.[37] However, these methods are plagued by the limitation of prolonged reaction times, low yields, tedious work up, inefficiency of method when aliphatic aldehydes are used in the reaction, and the use of expensive, hazardous, difficult to handle or unreusable catalysts.