Ultrasound-assisted one-pot synthesis of substituted coumarins catalyzed by poly(4-vinylpyridinium) hydrogen sulfate as an efficient and reusable solid acid catalyst

The liquid phase of 4,4'-trimethylenedipiperidine: a safe and greener dual-task agent for clean and facile synthesis of coumarin derivatives

A practical and facile synthesis of various coumarin derivatives was conducted using a liquid phase of 4,4'-trimethylenedipiperidine as a safe and greener dual-task reagent under catalyst-free and solvent-free conditions. This reagent is a commercially available solid and can be handled easily, having a liquid phase over a vast temperature range, high thermal stability, low toxicity, and good solubility in green solvents such as water and ethanol. It is worth mentioning that 4,4'-trimethylenedipiperidine could be completely recovered and regenerated after a simple process. The current method has other merits, including (a) minimizing the use of high-risk and toxic reagents and solvents; (b) the use of a secure and recoverable medium-organocatalyst instead of metal-based catalysts, (c) avoid tedious processes, harsh conditions, and a multi-step process for the preparation of catalysts, (d) transform phenol and salicyladehyde derivatives into the corresponding coumarin derivatives in good to high yields, (e) minimize hazardous waste generation. TMDP could be easily recovered and reused several times with no change in its activity. Furthermore, the current work demonstrated that the liquid phase of 4,4'-trimethylenedipiperidine can be a promising medium in organic reaction at higher temperatures due to its broad liquid range temperature, thermal stability, acceptor/donor hydrogen bond property, and other unique merits. New methodology for the synthesis of coumarines using liquid phase of TMDP under mild conditions.

A review on convenient synthesis of substituted coumarins using reuseable solid acid catalysts

Due to growing concern about chemicals and their impact on the environment, cleaner reaction conditions are needed to be incorporated into chemical synthetic procedures. Recently, the use of heteropolyacid catalysts, mainly reuseable solid acid catalysts, has gained a leading role in organic synthesis due to their environmental and economic considerations and industrial utilization. The high catalytic activity, moisture sensitivity, reusability and inexpensive makes solid supported reagents attractive substituents to conventional Lewis acids. Nowadays synthesis of coumarins and their derivatives has attracted considerable attention from organic and medicinal chemists for many years as a large number of natural products contain this heterocyclic nucleus. In continuation with our investigations into the synthesis of substituted coumarins and due to several advantages of heterogeneous catalysts viz. cost-effective, no side products, high yield of desired products and no toxic waste material, here we report a new approach for the synthesis of substituted coumarins using solid acid catalysts.

Syntheses and evaluation of daphnetin derivatives as novel G protein-coupled receptor inhibitors and activators

A series of daphnetin (7,8-dihydroxycoumarin) derivatives 1-22 were synthesized including sixteen new compounds (1-5, 7-14, 18, 21 and 22) and six known compounds (6, 15-17, 19 and 20). Their pharmacological activities on G protein-coupled receptors (GPCRs) were evaluated by double antibody sandwich ELISA (DAS-ELISA) in vitro. Daphnetin derivatives with various substitution patterns/groups were obtained from inhibitors to activators on GPCRs. Derivatives 2-5, 8, 15, 16 and 18-20 possessed moderate activation potency on GPCRs. Among them, derivatives 3-5, 16 and 19 presented significant activation potency on GPCRs with EC₅₀ values in the range of 1.18-1.91 nM. Derivatives 6, 11, 14 and 18 showed significant inhibitory potency on GPCRs with IC₅₀ values in the range of 1.26-1.38 nM. Moreover, the structure-activity relationships (SARs) of daphnetin derivatives were discussed in detail. The new daphnetic-based GPCRs activators and inhibitors have potentials as future drug candidates for the treatment of metabolic diseases.

Antagonists of Vitamin K-Popular Coumarin Drugs and New Synthetic and Natural Coumarin Derivatives

Many natural coumarins and their chemically synthesized analogs and derivatives exert diverse properties, such as anticancer, antioxidant, anti-inflammatory, or anticoagulant, with the latter being of the utmost importance. The widely used warfarin, acenocoumarol, and phenprocoumon exert anticoagulant properties by inhibiting the vitamin K epoxide reductase complex. In this interdisciplinary review, we present biochemical principles of the coagulation processes and possible methods for their tuning based on the use of coumarins. We also summarize chemical methods of synthesis of coumarins and discuss structures and properties of those that have been used for a long time, as well as newly synthesized compounds. Brief information on the clinical use of coumarins and other anticoagulant drugs is given, including the severe effects of overdosing and methods for reversing their action.

Heterogeneously Catalyzed Pechmann Condensation Employing the Tailored Zn0.925Ti0.075O NPs: Synthesis of Coumarin

A novel heterogeneous catalytic method was developed for the synthesis of coumarin and its derivatives using the Ti(IV)-doped ZnO matrix forming catalyst Zn_0.925Ti_0.075O having a high surface area and good Lewis acidity. The catalyst shows high activity toward a broad spectrum of the substituted phenols with β-ketoesters such as ethyl acetoacetate, ethyl butyryl acetate, ethyl benzoyl acetate, and so forth in good yields over short reaction times during the synthesis of coumarins. The methodology was further extended for the synthesis of ayapin molecules. The catalyst also shows recycle activity up to seven cycles with very good stability.

Ultrasound assisted Bradsher reaction in aqueous and non-aqueous media: First use of ultrasounds in electrophilic aromatic cyclisation leading to polyacenes

The present work describes the first use of ultrasounds in the Bradsher cyclisation of activated and non-activated ortho-formyl diarylmethanes. This reaction is also the first example of electrophilic, aromatic cyclisation assisted by ultrasounds which leads to pure polycyclic, fused aromatic hydrocarbons containing 3 and 4 fused rings in excellent yields. The reaction proceeds not only in aqueous but also in non-aqueous media at milder conditions (room temperature) and in much shorter reaction times than in conventional protocols.

Design for carbon–carbon bond forming reactions under ambient conditions

The carbon–carbon (C–C) bond forms the ‘backbone’ of nearly every organic molecule, and lies at the heart of the chemical sciences! Let us explore designing of carbon–carbon frameworks at ambient conditions.

Uncatalysed Production of Coumarin-3-carboxylic Acids: A Green Approach

A green contribution in short reaction times with moderate yields to produce coumarin-3-carboxylic acids is offered. Five different modes to activate the reactions (microwave, near-infrared, mechanical milling, and ultrasound) were compared with mantle heating in the presence or absence of ethanol, a green solvent. Near-infrared and microwave irradiations deliver the best yields in contrast to ultrasound and mechanical milling; moreover, these four processes offered shorter reaction times in comparison with the conventional mantle heating method. It is also important to highlight that the obtained molecules were produced without the requirement of a catalyst and two nonconventional energies forms are presented as new processes.

N-Sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate as an efficient and reusable solid acid catalyst for one-pot synthesis of xanthene derivatives in dry media under ultrasound irradiation

N-Sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate catalyzed efficiently the synthesis of xanthene derivatives under ultrasonic irradiation at room temperature, which has prompted various concerns involving cost and environmental persistence. This methodology shows the effect of presence of anion hydrogen sulfate as an important and effective factor on the promotion of the one-pot multi-components and condensation reactions. The catalyst can be recovered by simple filtration and used for several times without a significant loss of catalytic activity.

Ultrasound mediation for one-pot multi-component synthesis of amidoalkyl naphthols using new magnetic nanoparticles modified by ionic liquids

The ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium acetate was immobilized on the Fe3O4 nanoparticles (MNPs-IL-OAc) and used as an efficient new heterogeneous nanocatalyst for the one-pot multi-component synthesis of 1-amidoalkyl-2-naphthols under ultrasound irradiation. The advantages of present combined method are the use of a low scale catalyst, easier work-up procedure, waste-free, green and efficient synthetic entry to excellent yield of products in a high reusability and a short reaction time.

FeCl3-catalysed ultrasonic-assisted, solvent-free synthesis of 4-substituted coumarins. A useful complement to the Pechmann reaction

The catalytic activity of FeCl3 for the synthesis of a variety of 4-substituted coumarins using high energy techniques has been investigated. The ultrasonic-assisted conditions provide a useful complement to the Pechmann reaction, affording the coumarin derivatives in excellent yields, under solvent-free conditions, in short reaction times using an inexpensive, mild and benign Lewis acid catalyst.

Poly(4-vinylpyridine) supported acidic ionic liquid: a novel solid catalyst for the efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones under ultrasonic irradiation

A novel poly(4-vinylpyridine) supported acidic ionic liquid catalyst was synthesized by the reaction of 4-vinylpyridine with 1,3-propanesultone, followed by the polymerization and the addition of the heteropolyacid. Due to the combination of polymer features and ionic liquid, it acted as a heterogeneous catalyst to effectively catalyze the cyclocondensation reaction of anthranilamide with aldehydes under ultrasonic irradiation and afforded the corresponding 2,3-dihydro-4(1H)-quinazolinones compounds in good to excellent yields. In addition, the catalyst could be easily recovered by the filtration and reused six times without significant loss of catalytic activity. More importantly, the use of ultrasonic irradiation can obviously accelerate the reaction.