Solventless convenient synthesis of new cyano-2-aminopyridine derivatives from enaminonitriles

Domino Reaction for the Synthesis of Substituted Pyrano[3',4':3,4]cyclopenta[1,2-c]chromenes Involving Double Ring Formation

Herein, we present a green cascade approach for synthesizing a range of chemoselective polysubstituted pyrano[3',4':3,4]cyclopenta[1,2-c]chromenes containing a chiral stereocenter. The strategy involves a metal-free nucleophilic reaction between dialkyl (2E)-2-{2-oxo-3-[(2E)-3-aryl-2-propenoyl]-2H-chromen-4-yl}-2-butenedioates and α,α-dicyanoolefins under reflux conditions in ethanol solvent. Mechanistic studies have shown that the reaction proceeds via a cascade of steps, including Michael addition, intramolecular C- and O-cyclization, intramolecular trans-esterification, [1,2]-H and [1,5]-methoxy- and ethoxy carbonyl shift, and finally aromatization to yield the desired product. In this method, three bonds (2C-C and C-O) form in one pot, simultaneously forming two new cyclopentane and pyrano rings by double cyclization reactions. Other advantages of this method are that it has a simple operation, readily available starting materials, a chemoselective cascade process, transition metal-free, synthetically useful yields, and green conditions by using ethanol as a solvent.

Synthesis of novel aryl-substituted 2-aminopyridine derivatives by the cascade reaction of 1,1-enediamines with vinamidinium salts to develop novel anti-Alzheimer agents

Alzheimer's disease (AD), a severe neurodegenerative disorder, imposes socioeconomic burdens and necessitates innovative therapeutic strategies. Current therapeutic interventions are limited and underscore the need for novel inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), enzymes implicated in the pathogenesis of AD. In this study, we report a novel synthetic strategy for the generation of 2-aminopyridine derivatives via a two-component reaction converging aryl vinamidinium salts with 1,1-enediamines (EDAMs) in a dimethyl sulfoxide (DMSO) solvent system, catalyzed by triethylamine (Et3N). The protocol introduces a rapid, efficient, and scalable synthetic pathway, achieving good to excellent yields while maintaining simplistic workup procedures. Seventeen derivatives were synthesized and subsequently screened for their inhibitory activity against AChE and BChE. The most potent derivative, 3m, exhibited an IC50 value of 34.81 ± 3.71 µM against AChE and 20.66 ± 1.01 µM against BChE compared to positive control donepezil with an IC50 value of 0.079 ± 0.05 µM against AChE and 10.6 ± 2.1 µM against BChE. Also, detailed kinetic studies were undertaken to elucidate their modes of enzymatic inhibition of the most potent compounds against both AChE and BChE. The promising compound was then subjected to molecular docking and dynamics simulations, revealing significant binding affinities and favorable interaction profiles against AChE and BChE. The in silico ADMET assessments further determined the drug-like properties of 3m, suggesting it as a promising candidate for further pre-clinical development.

Ultrasound-promoted synthesis of novel N-arylamino-3,5′-biquinoline derivatives: their applications in live-cell imaging and in vitro anticancer activity evaluation

A novel strategy for the construction of functionalized N-arylamino-3,5′-biquinoline has been developed.

Ecofriendly Synthesis of Formamidine Derivatives Catalyzed by Al-MCM- 41 Mesoporous Materials

Abstract:

Formamidine derivatives have been synthesized in excellent yields at room temperature from primary amine and N,N-dimethylformamide dimethylacetal (DMF-DMA) in the presence of a catalytic amount of Al-MCM-41 synthesized from natural bentonite as silica and aluminum source. The advantages of this method are the use of a cheap, stable, non-toxic, and readily available catalyst, easy work-up, improved yields, and solvent-free conditions.

Cu(OAc)2/DABCO-mediated domino reaction of vinyl malononitriles with cyclic sulfamidate imines: access to 6-hydroxyaryl-2-aminonicotinonitriles

A novel Cu(II)-salt/DABCO-mediated one-pot access to a myriad of highly substituted biologically relevant 2-aminonicotinonitriles possessing a resourceful phenolic moiety with satisfactory yields is reported. This method involves cyclic sulfamidate imines as 1C1N sources and different kinds of acyclic/cyclic vinyl malononitriles as 4C sources for pyridine synthesis via a vinylogous Mannich-cycloaromatization sequence process, creating two new C-N bonds under mild conditions. Importantly, this de novo strategy is applicable to gram-scale syntheses, underlining the method's practicability and allowing for a wide range of substrates with excellent functional group tolerance.

Recent advances in the synthesis of cyclic compounds using α,α-dicyanoolefins as versatile vinylogous nucleophiles

This article provides a review of the applications of α,α-dicyanoolefins as versatile vinylogous nucleophiles in the synthesis of various cyclic compounds, covering the literature from the past 13 years.

Synthesis of multi-substituted pyridines from ylidenemalononitriles and their emission properties

Numerous methodologies to obtain pyridines from ylidenemalononitriles are described in the literature. Nevertheless, they are limited to the use of microwave or conventional heat and few lead to 2,3,4 or 2,3,4,5-substituted pyridines as multi-proposal molecular scaffolds or even universal pyridines. Herein, we present a mild and facile solvent-free methodology to obtain a scope of multi-substituted pyridines at room temperature. We also report an example where one of the resulting amino-nicotinonitriles exhibits a preliminary evidence of aggregation-induced emission (AIE).

Synthesis of Substituted Phthalimides via Ultrasound-Promoted One-Pot Multicomponent Reaction

In this work, a novel strategy for the straightforward synthesis of substituted phthalimides is described, which includes base-mediated Michael addition/intramolecular cyclization/[1,5]-H shift/cleavage of CS₂/aromatization/nucleophilic acyl substitution reaction of 2-(4-oxo-2-thioxothiazolidin-5-ylidene)acetates and α,α-dicyanoolefines under ultrasound (US) irradiation. Some advantages of this method are as follows: having simple operation, easily accessible starting materials, chemoselective cascade process, synthetically useful yields, and green conditions by utilizing US irradiation as a source of energy and using ethanol as solvent.

Increasing Scope of Clickable Fluorophores: Electrophilic Substitution of Ylidenemalononitriles

Recently, we demonstrated that ylidenemalononitriles (YMs) react with amines to form cyclic amidines and that the starting linear YMs are nonemissive in solution and the cyclic amidines are fluorescent. These turn-on systems were of interest to us because of their potential as biosensors and synthons for accessing functionalized pyridines. While our original method was promising, several limitations persisted, including access to more functionalized and polar-solvent-soluble structures as well as increased control over the rate of cyclization. Herein, we report a new approach that allows the electrophilic substitution of YMs. These substituted YMs exhibit faster turn-on rates, color tunability, access to polar-solvent-soluble species, and increased control over cyclization rate. This allowed us to significantly expand the fluorophore's chemical space.

Orthoamide und Iminiumsalze, XCVIa. Push-pull-substituierte 1,3,5-Hexatriene aus Orthoamiden von Alkincarbonsäuren und Birckenbach-analogen Acetophenonen

From acetone and the orthoamide of phenylpropiolic acid (21b) N,N-dimethyl-phenylpropiolic acid amide (24) is formed. In contrast, the reaction of chloroacetone (28) with 21b results in the vinylogous guanidinium chloride 29. Unexpectedly, the Birckenbach-analogoue ethyl methyl ketone (34) reacts with the orthoamide 21b to give the push-pull-substituted butadiene 36. In contrast to this observation, the reaction of the Birckenbach-analogous acetophenones 30 with the orthoamides 21a – c delivers the push-pull-substituted 1,3,5-hexatrienes 31a – j.

Sustainable Synthetic Approach for (Pyrazol-4-ylidene)pyridines By Metal Catalyst-Free Aerobic C(sp2)-C(sp3) Coupling Reactions between 1-Amino-2-imino-pyridines and 1-Aryl-5-pyrazolones

A novel, metal catalyst-free, and efficient method has been developed for the synthesis of (pyrazol-4-ylidene)pyridine derivatives. The process involves dehydrogenative coupling of 1-amino-2-imino-pyridines with 1-aryl-5-pyrazolone derivatives utilizing O2 as the sole oxidant. The new method benefits from a high atom economy, efficiency, and substrate scope, as well as the simplicity of reaction and product purification procedures.

Scalable Sonochemical Synthetic Strategy for Pyrazolo[1,5-a]pyridine Derivatives: First Catalyst-Free Concerted [3 + 2] Cycloaddition of Alkyne and Alkene Derivatives to 2-Imino-1H-pyridin-1-amines

A highly efficient and convenient one-pot sonochemical synthetic strategy has been sophisticated for synthesizing a novel class of polysubstituted pyrazolo[1,5-a]pyridines via [3 + 2] cycloaddition of dialkyl acetylenedicarboxylates, ethyl propiolate, and alkenes to 2-imino-1H-pyridin-1-amines under catalyst-free conditions. A series of uniquely substituted pyrazolo[1,5-a]pyridines has been synthesized with a very good to excellent yield, and the mechanistic pathway that involves a [3 + 2] annulation process was also proposed. In this study, several spectroscopic tools of analyses were employed for structure elucidation, and the X-ray single-crystal technique was utilized to confirm the proposed mechanism and the regioselectivity.

Synthesis and Pharmacological Activities of Pyrano[2,3-d]pyrimidine and Pyrano[2,3-d]pyrimidine-5-one Derivatives as New Fused Heterocyclic Systems

Various fused oxazine such as 4-(4-methoxyphenyl)-3,7-dimethyl-1,4-dihydro-5H-pyrazolo [4′,3′:5,6]pyrano[2,3-d][1,3]oxazin-5-one2has been prepared and utilized as a starting material for novel pyrazolopyranopyrimidinones3,5,6, and7a–cand pyrazolopyranopyrimidines4,9,10, and11which are expected to possess considerable chemical and pharmacological activities. The structures of the new compounds have been elucidated by spectroscopic data and elemental analysis. The antioxidant and anticancer activities of synthesized products have been evaluated.

Cubic Perovskite ZnTiO3 Nanopowder as a Recyclable Heterogeneous Catalyst for the Synthesis of 1,6-Naphthyridines in Water

Cubic perovskite ZnTiO₃ nanopowder has been prepared by means of a sustainable sol-gel method. The nanopowder (12-20 nm) has been thoroughly characterized by N₂ sorption analysis, high-resolution (HR) TEM, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), SEM, and FTIR analyses. The environmentally benign synthesis of highly substituted 1,6-naphthyridines catalyzed by ZnTiO₃ nanopowder in aqueous media has been demonstrated. It requires two different catalytic functions, that is, an acid one, which is provided by Ti^IV ions, and a basic one, which is provided by the oxide ion incorporated within the ZnTiO₃ metal oxide framework. 1,6-Naphthyridines are of tremendous biological importance, and this method is simple and environmentally friendly. The greenness of the process was satisfactorily established as water was exploited as the reaction medium and there was very high atom economy.