General one-pot, two-step protocol accessing a range of novel polycyclic heterocycles with high skeletal diversity

5-Endo Trig Oxidative Radical Cyclizations of Ugi-3CR Products toward 1,4-Imidazolidinones

A 5-endo trig oxidative radical cyclization of benzylamine-derived Ugi three-component reaction products rapidly affords imidazolidinones with three diversity elements. This adaptation of our previously described multicomponent reaction-oxidation methodology further showcases manipulation of the diversity elements in multicomponent reaction products via oxidative radical cyclizations, which generates highly decorated privileged heterocycles.

Two decades of recent advances of Ugi reactions: synthetic and pharmaceutical applications

Multicomponent reactions (MCRs) are powerful synthetic tools in which more than two starting materials couple with each other to form multi-functionalized compounds in a one-pot process, the so-called “tandem”, “domino” or “cascade” reaction, or utilizing an additional step without changing the solvent, the so-called a sequential-addition procedure, to limit the number of synthetic steps, while increasing the complexity and the molecular diversity, which are highly step-economical reactions. The Ugi reaction, one of the most common multicomponent reactions, has recently fascinated chemists with the high diversity brought by its four- or three-component-based isonitrile. The Ugi reaction has been introduced in organic synthesis as a novel, efficient and useful tool for the preparation of libraries of multifunctional peptides, natural products, and heterocyclic compounds with stereochemistry control. In this review, we highlight the recent advances of the Ugi reaction in the last two decades from 2000–2019, mainly in the synthesis of linear or cyclic peptides, heterocyclic compounds with versatile ring sizes, and natural products, as well as the enantioselective Ugi reactions. Meanwhile, the applications of these compounds in pharmaceutical trials are also discussed.

We highlight the recent advances of the Ugi reaction in the last two decades from 2000–2019, mainly in the synthesis of linear or cyclic peptides, heterocyclic compounds with versatile ring sizes, and natural products, as well as the enantioselective Ugi reactions.

Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides

The synthesis of a novel category of pseudo-peptides via intramolecular Ugi reaction of levulinic acid (4-oxopentanoic acid), aromatic and aliphatic amines, and amino acid-based isocyanides is reported. Levulinic acid was applied as a bifunctional substrate containing both carbonyl and acid moieties suitable for the Ugi reaction. This article provides a facile and convenient one-pot procedure for the synthesis of peptide-like heterocyclic molecules containing 2-pyrrolidone (γ-lactam), amide and ester functional groups with good to excellent yields.

A diversity-oriented novel regioselective synthesis of sulfonamide–thiazolidinone hybrids

A regioselective multicomponent approach to sulfonamide–thiazolidinone hybrids has been developed.

To each his own: isonitriles for all flavors. Functionalized isocyanides as valuable tools in organic synthesis

The term functionalized isocyanides refers to all those isocyanides in which a neighbouring functional group can finely tune the reactivity of the isocyano group or can be exploited in post-functionalization processes. In this manuscript, we have reviewed all the isocyanides in which the pendant functional group causes either deviation from or reinforces the normal reactivity of the isocyano group and categorized them to highlight their common features and differences. An analysis of their synthetic potential and the possible unexplored directions for future research studies is also addressed.

Synthesis of Constrained Heterocycles Employing Two Post-Ugi Cyclization Methods for Rapid Library Generation with In Cellulo Activity

Benzimidazoles and quinoxalinones are present in the core of many pharmacologically relevant compounds. Several combinatorial methods have been developed to attach ring systems to both scaffolds for derivatization at select positions. Herein, we describe the development of novel constrained heterocyclic compounds attached to the N1 position of both benzimidazole and quinoxalinone scaffolds. Utilizing robust post-Ugi cyclization methods, including the Ugi-deprotection-cyclization (UDC) methodology, allows for efficient access to a new area of chemical space. Additionally, molecular modeling and in cellulo screening was employed to therapeutically validate the compounds formed with this method.

Two Cycles with One Catch: Hydrazine in Ugi 4-CR and Its Postcyclizations

Isocyanide-based multicomponent reactions (IMCR) are by far the most versatile reactions that can construct relatively complex molecules by one-pot synthesis. More importantly, the development of post IMCR modifications significantly improves the scaffold’s diversity. Here, we describe the use of N-Boc protected hydrazine together with α-amino acid derived isocyanides in the Ugi tetrazole reaction and its post cyclization under both acidic and basic conditions. The cyclization in acidic conditions was conducted in a one pot fashion, which give 7-aminotetrazolopyrazinone (6) and tetrazolotriazepinone (7) cyclic products. The post cyclization under basic condition could selectively afford Boc-protected 7-aminotetrazolopyrazinone (8) products in yield of 38–87%.

Combinatorial synthesis, in silico, molecular and biochemical studies of tetrazole-derived organic selenides with increased selectivity against hepatocellular carcinoma

Novel tetrazole-based diselenides and selenoquinones were synthesized via azido-Ugi and sequential nucleophilic substitution (SN) strategy. Molecular docking study into mammalian TrxR1 was used to predict the anticancer potential of the newly synthesized compounds. The cytotoxic activity of the compounds was evaluated using hepatocellular carcinoma (HepG2) and breast adenocarcinoma (MCF-7) cancer cells and compared with their cytotoxicity in normal fibroblast (WI-38) cells. The corresponding redox properties of the synthesized compounds were assessed employing 2,2-diphenyl-1-picrylhydrazyl (DPPH), glutathione peroxidase (GPx)-like activity and bleomycin dependent DNA damage. In general, diselenides showed preferential cytotoxicity to HepG2 compared to MCF-7 cells. These compounds exhibited also good GPx catalytic activity compared to ebselen (up to 5 fold). Selenoquinones 18, 21, 22 and 23 were selected to monitor the expression levels of caspase-8, Bcl-2 and Ki-67 molecular biomarkers. Interestingly, these compounds downregulated the Bcl-2 and Ki-67 expression levels and activated the expression of caspase-8 in HepG2 cells compared to untreated cells. These results indicate that some of the newly synthesized compounds possess anti-HepG2 activity.

Iron(II) Halide Promoted Cyclization of Cyclic 2-Enynamides: Stereoselective Synthesis of Halogenated Bicyclic γ-Lactams

A simple and mild process was developed for the highly stereoselective synthesis of halogenated bicyclic [4.3.0] and [3.3.0] γ-lactams, possessing four stereocenters, from easily available cyclic 2-enynamides. The reaction required only an inexpensive iron(II) halide under dry air and was tolerant of aryl, heteroaryl, and alkyl groups at the alkyne terminus.

Recent advances in the synthesis of benzimidazol(on)es via rearrangements of quinoxalin(on)es

The review describes all the quinoxaline-benzimidazole rearrangements as a whole and the new quinoxalinone-benzimidazol(on)e rearrangements in particular when exposed to nucleophilic rearrangements which can be used for the synthesis of various biheterocyclic motifs.

Theophylline as the catalyst for the diastereoselective synthesis of trans-1,2-dihydrobenzo[a]furo[2,3-c]phenazines in water

Theophylline-catalyzed efficient and environmentally benign procedure for the diastereoselective synthesis of trans-1,2-dihydrobenzo[a]furo[2,3-c]phenazines with pyridinium ylide assisted domino reaction in water.

An efficient microwave-assisted synthesis of cotinine and iso-cotinine analogs from an Ugi-4CR approach

A convenient synthesis of cotinine and iso-cotinine analogs featuring an Ugi-4CR/cyclization approach.

Ugi-based approaches to quinoxaline libraries

An expedient and concise Ugi-based unified approach for the rapid assembly of quinoxaline frameworks has been developed. This convergent and versatile method uses readily available commercial reagents, does not require advanced intermediates, and exhibits excellent bond-forming efficiency, thus exemplifying the operationally simple synthesis of quinoxaline libraries.

Synthesis of diverse nitrogen-enriched heterocyclic scaffolds using a suite of tunable one-pot multicomponent reactions

Five elegant and switchable three-component reactions which enable access to a new series of nitrogen-containing heterocycles are reported. A novel one-step addition of an isocyanide to a hydrazine derived Schiff base affords unique six-membered pyridotriazine scaffolds (A and E). With slight modification of reaction conditions and replacement of the nucleophilic isocyanide moiety with different electrophiles (i.e., isocyanates, isothiocyanates, cyclic anhydrides, and acyl chlorides) five-membered triazolopyridine scaffolds (B, D, F, G) are generated in a single step. Furthermore, the use of phenyl hydrazine enables access to dihydroindazole-carboxamides, devoid of a bridge-head nitrogen (C). All protocols are robust and tolerate a diverse collection of reactants, and as such, it is expected that the new scaffolds and associated chemistry will garner high interest from medicinal chemists involved in either file enhancement or specific target-related drug discovery campaigns.

Novel succinct routes to Quinoxalines and 2-Benzimidazolylquinoxalines via the Ugi reaction

This communication reveals a unique, user-friendly, concise two-step, one-pot protocol for the synthesis of highly substituted quinoxalines. Conducting the Ugi reaction with appropriately functionalized classical Ugi reagents with subsequent acid treatment of the Ugi adduct affords collections of diversified quinoxalines in good to excellent yields. The methodology exploits what may be viewed as a 'convertible carboxylic acid', which in addition may be captured in an intramolecular sense to generate structurally complex 2-benzimidazolylquinoxalines in a mere two steps.

A one-pot multicomponent coupling/cyclization for natural product herbicide (±)-thaxtomin A

The herbicide (±)-thaxtomin A has been synthesized in a one-pot two step process through an Ugi reaction followed by base-mediated cyclization.

L-proline catalyzed multicomponent reactions: facile access to 2H-benzo[g]pyrazolo[3,4-b]quinoline-5,10(4H,11H)-dione derivatives

Three component reaction of 2-hydroxy 1,4-naphthoquinones, aldehydes, and aminopyrazoles in the presence of a catalytic amount ofl-proline has been described for the synthesis of a series of 2H-benzo[g]pyrazolo[3,4-b]quinoline-5,10(4H,11H)-dione derivatives.

A simple one-pot 2-step N-1-alkylation of indoles with α-iminoketones toward the expeditious 3-step synthesis of N-1-quinoxaline-indoles

A straightforward procedure for the preparation of N-quinoxaline-indoles is presented. A base-catalyzed one-pot addition of indoles to a preformed α-iminoketone proceeds on the N-1 indole and the subsequent adduct undergoes an acid-mediated deprotection of an internal amino nucleophile, intramolecular cyclization and final oxidation generating N-1-quinoxaline-indoles in good yield.

Aldol reactions in multicomponent reaction based domino pathways: a multipurpose enabling tool in heterocyclic chemistry

The aldol reaction has been evaluated in combination with the Ugi multicomponent reaction to assemble richly decorated mono- and polycyclic systems via expeditious cascade pathways. A small collection of pyrrolinones was generated thereof, and the scarcely accessible pyridoquinoxalinedione scaffold was also prepared by designing an additional nucleophilic substitution step in this domino sequence requiring minimal operational effort.