Silver Nitrate-Catalyzed Isocyanide Insertion/Lactamization Sequence to Imidazolones and Quinazolin-4-ones: Development and Application in Natural Product Synthesis

Silver-catalyzed P-centered anion nucleophilic addition to isocyanide: access to 2-phosphinoyl indoles/indol-3-ols

A silver-catalyzed chemoselective cascade nucleophilic addition of a P-centered anion to isocyanides and cyclization reaction was developed for the efficient and practical synthesis of a wide range of 2-phosphinoyl indole and indol-3-ol derivatives. Unlike the well-documented synthesis of phosphorus-functionalized heterocycles via a P-centered radical, an anionic reactivity profile of phosphine oxides is most likely involved in this domino transformation.

A Phosphine-Free Air-Stable Mn(II)-Catalyst for Sustainable Synthesis of Quinazolin-4(3H)-ones, Quinolines, and Quinoxalines in Water

The synthesis, characterization, and catalytic application of a new phosphine-free, well-defined, water-soluble, and air-stable Mn(II)-catalyst [Mn(L)(H2O)2Cl](Cl) ([1]Cl) featuring a 1,10-phenanthroline based tridentate pincer ligand, 2-(1H-pyrazol-1-yl)-1,10-phenanthroline (L), in dehydrogenative functionalization of alcohols to various N-heterocycles such as quinazolin-4(3H)-ones, quinolines, and quinoxalines are reported here. A wide array of multisubstituted quinazolin-4(3H)-ones were prepared in water under air following two pathways via the dehydrogenative coupling of alcohols with 2-aminobenzamides and 2-aminobenzonitriles, respectively. 2-Aminobenzyl alcohol and ketones bearing active methylene group were used as coupling partners for synthesizing quinoline derivatives, and various quinoxaline derivatives were prepared by coupling vicinal diols and 1,2-diamines. In all cases, the reaction proceeded smoothly using our Mn(II)-catalyst [1]Cl in water under air, affording the desired N-heterocycles in satisfactory yields starting from cheap and readily accessible precursors. Gram-scale synthesis of the compounds indicates the industrial relevance of our synthetic strategy. Control experiments were performed to understand and unveil the plausible reaction mechanism.

Synthesis of bioactive evodiamine and rutaecarpine analogues under ball milling conditions

Mechanochemical reactions achieved by processes such as milling and grinding are promising alternatives to traditional solution-based chemistry. This approach not only eliminates the need for large amounts of solvents, thereby reducing waste generation, but also finds applications in chemical and materials synthesis. The focus of this study is on the synthesis of quinazolinone derivatives by ball milling, in particular evodiamine and rutaecarpine analogues. These compounds are of interest due to their diverse bioactivities, including potential anticancer properties. The study examines the reactions carried out under ball milling conditions, emphasizing their efficiency in terms of shorter reaction times and reduced environmental impact compared to conventional methods. The ball milling reaction of evodiamine and rutaecarpine analogues resulted in yields of 63-78% and 22-61%, respectively. In addition, these compounds were tested for their cytotoxic activity, and evodiamine exhibited an IC50 of 0.75 ± 0.04 μg mL-1 against the Ca9-22 cell line. At its core, this research represents a new means to synthesise these compounds, providing a more environmentally friendly and sustainable alternative to traditional approaches.

Exploring amine-rich supramolecular silver(I) metallogels for autonomous self-healing and as catalysts for a three component coupling reaction

A series of Ag(I) supramolecular organo-aqueous gels have been synthesized in the presence of an amine-rich triazole ligand as a gelator. Judicious choice of the triazole derivative and counter anion allows a desired spatial orientation of the pendant amine functionality to accentuate the gelation ability and autonomous self-healability via hydrogen bonding. In addition, the hydrogen bond donors, i.e. pendant -NH2 groups, offer a critical proximity of counter anions to the Lewis acidic Ag(I) and the reactants for promoting a three component coupling reaction of an aldehyde, a terminal alkyne and an amine, giving expedient access to propargyl amines, with remarkable functional group tolerance for both aromatic and aliphatic aldehydes, and aryl acetylenes. Experiments substantiate the pivotal role of counter anions and H-bonding interactions in the observed preference for propargylamines over the diacetylene by-product. Our catalyst is robust, bench-stable, and recyclable, and demonstrates a catalytic efficiency comparable to or better than those of reported systems. The catalyst was found equally effective for the gram-scale synthesis of propargylamines. Our approach lies at the intersection of metal-based, H-bond-mediated counter anion-tuned catalysis, evincing a potential for the development of purpose-built supramolecular gels for desired catalytic applications in the future.

Charting the Chemical Reaction Space around a Multicomponent Combination: Controlled Access to a Diverse Set of Biologically Relevant Scaffolds

Charting the chemical reaction space around the combination of carbonyls, amines, and isocyanoacetates allows the description of new multicomponent processes leading to a variety of unsaturated imidazolone scaffolds. The resulting compounds display the chromophore of the green fluorescent protein and the core of the natural product coelenterazine. Despite the competitive nature of the pathways involved, general protocols provide selective access to the desired chemotypes. Moreover, we describe unprecedented reactivity at the C-2 position of the imidazolone core to directly afford C, S, and N-derivatives featuring natural products (e.g. leucettamines), potent kinase inhibitors, and fluorescent probes with suitable optical and biological profiles.

Charting the Chemical Reaction Space around a Multicomponent Combination: Controlled Access to a Diverse Set of Biologically Relevant Scaffolds

Charting the chemical reaction space around the combination of carbonyls, amines, and isocyanoacetates allows the description of new multicomponent processes leading to a variety of unsaturated imidazolone scaffolds. The resulting compounds display the chromophore of the green fluorescent protein and the core of the natural product coelenterazine. Despite the competitive nature of the pathways involved, general protocols provide selective access to the desired chemotypes. Moreover, we describe unprecedented reactivity at the C-2 position of the imidazolone core to directly afford C, S, and N-derivatives featuring natural products (e.g. leucettamines), potent kinase inhibitors, and fluorescent probes with suitable optical and biological profiles.

tert-Butyl Hydroperoxide Promoted the Reaction of Quinazoline-3-oxides with Primary Amines Affording Quinazolin-4(3H)-ones

An efficient and facile approach for the synthesis of quinazolin-4(3H)-ones via the reaction of quinazoline-3-oxides with primary amines is described. This approach is demonstrated to be applicable for a broad range of substrates and proceeds efficiently under metal-free and mild reaction conditions employing easily available tert-butyl hydroperoxide as the oxidant. Remarkably, 3-(2-(1H-indol-3-yl) ethyl)quinazolin-4(3H)-one 3w, which was conveniently obtained by this process in 70% yield, was an excellent precursor for the synthesis of bioactive evodiamine and rutaempine.

Silver-promoted dearomative [3+4] cycloaddition of anthranils with α-isocyanoacetates: access to benzodiazepines

The first example of silver-promoted [3+4] cycloaddition of α-isocyanoacetates with anthranils as aromatic Michael accepters, offering access to benzo[d][1,3]diazepinones, has been developed. Mechanistic studies revealed that an "oxygen migration" rearrangement process was involved in this dearomative cycloaddition reaction. Additionally, benzo[d][1,3]diazepinones were obtained efficiently as well under catalytic conditions. Broad functional groups were well tolerated under mild reaction conditions.

Synthesis of pyrimidine-containing alkaloids

This review deals with the synthesis of naturally occurring alkaloids containing partially or completely saturated pyrimidine nuclei. The interest in these compounds is associated with their structural diversity, high biological activity and toxicity. The review is divided into four parts, each of which describes a number of synthetic methodologies toward structurally different naturally occurring alkaloids containing saturated cyclic six-membered amidine, guanidine, aminal and urea (thiourea) moieties, respectively. The development of various synthetic strategies for the preparation of these compounds has remarkably increased during the past few decades. This is primarily due to the fact that some of these compounds are isolated only in limited quantities, which makes it practically impossible to study their full structural characteristics and biological activity.

The Synthesis, Structural Modification and Mode of Anticancer Action of Evodiamine: a review

BACKGROUND

Finding novel antitumor reagents from naturally occurring alkaloids is a widely accepted strategy. Evodiamine, a tryptamine indole alkaloid isolated from Evodia rutaecarpa, has a wide range of biological activities, such as antitumor, anti-inflammation, and anti-bacteria. Hence, research works on the structural modification of evodiamine will facilitate the discovery of new antitumor drugs.

OBJECTIVE

The recent advances in the synthesis of evodiamine, and studies on the drug design, biological activities, and structure-activity-relationships of its derivatives, published in patents and primary literatures, are reviewed in this paper.

METHODS

The literatures, including patents and follow-up research papers from 2015 to 2020, related to evodiamine is searched in the Scifinder, PubMed, Espacenet, China National Knowledge Infrastructure (CNKI), and Wanfang databases. The key words are evodiamine, synthesis, modification, anticancer, mechanism.

RESULTS

The synthesis of evodiamine are summarized. Then, structural modifications of evodiamine are described, and the possible modes of actions are discussed.

CONCLUSION

Evodiamine has a 6/5/6/6/6 ring system, and the structural modifications are focused on ring A, D, E, C5, N-13, and N-14. Some compounds show promising anticancer potentials and warrant further study.

Cu/base co-catalyzed [3+3] cycloaddition for the synthesis of highly functionalized 4-fluoropyridines

An efficient, straightforward and general method for the de novo synthesis of highly functionalized 4-fluoropyridines was developed via a cooperative copper- and base-catalyzed [3+3] cycloaddition of active methylene isocyanides with difluorocyclopropenes. The resulting 4-fluoropyridines can be readily diversified by various nucleophiles.

Chemoselective Reactions of Isocyanates with Secondary Amides: One-Pot Construction of 2,3-Dialkyl-Substituted Quinazolinones

A facile method for the preparation of 2,3-dialkyl-substituted quinazolinones from readily available N-arylamides and commercial isocyanates was developed. This one-pot procedure involves the chemoselective activation of the secondary amide with Tf₂O/2-Br-Pyr, the sequential addition of isocyanate, and cyclization. The mild reaction is general for a wide range of substrates and can be run on a gram scale.

Recent advances in multi-component reactions and their mechanistic insights: a triennium review

This review summarizes the recent developments in MCRs, incorporating different strategies along with their mechanistic aspects.

Synthesis of Quinazolin-4-ones by Copper-Catalyzed Isocyanide Insertion

Herein, we report a novel copper-catalyzed imidoylative cross-coupling/cyclocondensation reaction between 2-isocyanobenzoates and amines efficiently producing quinazolin-4-ones. The reaction utilizes Cu(II) acetate as an environmentally benign catalyst in combination with a mild base and proceeds well in anisole, a recommended, sustainable solvent. Additionally, the reaction does not require dry conditions or inert atmospheres for optimal performance. The scope of this isocyanide insertion reaction is rather broad, tolerating various functionalized isocyanobenzoates and a range of substituted amines, although the use of aromatic amines as nucleophiles requires microwave heating.

Electrosynthesis of polycyclic quinazolinones and rutaecarpine from isatoic anhydrides and cyclic amines

A direct decarboxylative cyclization between readily available isatoic anhydrides and cyclic amines was established to construct polycyclic fused quinazolinones employing electrochemical methods. This procedure was performed in an undivided cell without the use of a transition-metal-catalyst and external oxidant. A broad scope of polycyclic fused quinazolinones were obtained in moderate to good yields. Additionally, rutaecarpine was also prepared through our method in one step in good yield.

Polycyclic quinazolinones and rutaecarpine were synthesized from isatoic anhydrides and cyclic amines through an electrochemical method without an external oxidant and transition-metal-catalyst.

Domino synthesis of fully substituted pyridines by silver-catalyzed chemoselective hetero-dimerization of isocyanides

A silver-catalyzed hetero-dimerization of various vinyl isocyanides with isocyanoacetamides has been developed for the efficient and practical synthesis of fully substituted pyridines in a single operation.

TFA/TBHP-promoted oxidative cyclisation for the construction of tetracyclic quinazolinones and rutaecarpine

An efficient TFA/TBHP-promoted oxidative cyclisation of readily available isatins with 1,2,3,4-tetrahydroisoquinolines has been firstly developed. The potential utility of this strategy was demonstrated by one-step synthesis of a natural alkaloid Rutaecarpin.

Transition-metal and oxidant-free approach for the synthesis of diverse N-heterocycles by TMSCl activation of isocyanides

A highly efficient TMSCl-mediated addition of N-nucleophiles to isocyanides has been achieved. This transition-metal and oxidant-free strategy has been applied to the construction of various N-heterocyles such as quinazolinone, benzimidazole and benzothiazole derivatives by the use of distinct amino-based binucleophiles. The notable feature of this protocol includes its mild reaction condition, broad functional group tolerance and excellent yield.

A highly efficient TMSCl-mediated addition of N-nucleophiles to isocyanides has been achieved.

Facile access to evodiakine enabled by aerobic copper-catalyzed oxidative rearrangement

Oxidation as a fundamentally important method for the synthesis of complex structures is difficult to achieve in a selective manner. Evodiakine, a complex natural product possessing an unprecedented ring system (6/5/5/7/6), has a high oxidation state without a practical solution. Herein, we report the first synthesis of evodiakine via aerobic copper-catalyzed late-stage functionalization of evodiamine.

Pd-Catalyzed multicomponent reaction of sulfonyl azides, primary amines and methyl α-isocyanoacetates: highly efficient synthesis of tetrasubstituted imidazolone derivatives

A highly efficient Pd-catalyzed multicomponent reaction of sulfonyl azides, primary amines and methyl α-isocyanoacetates was developed.

A concise synthesis and biological study of evodiamine and its analogues

Efficient access to evodiamine and its analogues is presented via Lewis acid catalysis. In this reaction, three chemical bonds and two heterocyclic-fused rings are constructed in one step.

Three-Component Reactions to Spirocyclic Pyrrolidinonylformimidamides: α-Isocyano Lactams as Two-Atom Unit in Silver-Catalyzed Formal [3 + 2] Cycloaddition Reactions

A facile approach to spirocyclic pyrrolidinonylformimidamides has been developed via three-component reactions of isocyanides, alkenes, and amines. The reaction proceeds through a sequence of two distinct reaction pathways; the base-catalyzed conjugate addition of α-isocyano lactams to electron-deficient alkenes and the Ag(I)-catalyzed amine insertion to the isocyanide moiety. Both reactions display markedly different reaction kinetics, allowing the one-pot three-component reactions to be performed in the presence of respective catalysts, a Brønsted base and a silver salt. The formation of spirocyclic pyrrolidin-2-ones represents an unusual use of α-isocyano lactam as a two-atom unit in a formal [3 + 2] cycloaddition reaction. The successful identification of ways to defy the typical three-atom unit role of α-isocyano carbonyl compounds in the [3 + 2] cycloaddition pathways manifests a rapid assembly of medicinally important spirocyclic scaffolds from readily available starting materials.

Synthesis of 2-Aminoimidazolones and Imidazolones by (3 + 2) Annulation of Azaoxyallyl Cations

The first examples of (3 + 2) annulations between azaoxyallyl cations and cyanamides and nitriles to give the corresponding 2-aminoimidazolones and imidazolones are reported. On the basis of the isolation of unexpected imidate products with certain substrates, it is proposed that the reaction proceeds via fast kinetic O-alkylation followed by rearrangement to the thermodynamically favored 2-aminoimidazolones and imidazolones. The method was applied to the formal synthesis of the antihypertensive drug irbesartan.