Synthesis and biological evaluation of novel N-aryl maleimide derivatives clubbed with α-hydroxyphosphonates

Recent advances in the transformation of maleimides via annulation

Over the past five years, maleimide scaffolds have gained considerable attention in organic synthesis for their role in forming cyclized molecules through annulation and C-H activation. As versatile and reactive coupling agents, maleimides have enabled the efficient synthesis of various cyclized products, including annulation, benzannulation, cycloaddition, and spirocyclization, with applications in medicinal chemistry, drug discovery, and materials science. Despite the extensive study of maleimide chemistry, certain reactions-such as cycloaddition-based annulation, photoannulation, and electrochemical transformations-remain underexplored despite their promising potential in the pharmaceutical and chemical industries. Recent advancements, such as photocatalysis and electrochemical methods, have expanded the utility of maleimides, providing more sustainable and selective approaches for synthesizing complex molecules. This review compiles research published between 2019 and 2024, highlighting the substrate scope, reaction diversity, and industrial relevance of maleimide-based annulation strategies. Additionally, we discuss emerging trends and future directions in maleimide chemistry, exploring opportunities for novel reaction pathways and broader applications in synthetic biology and materials science.

Two distinct protocols for the synthesis of unsymmetrical 3,4-disubstituted maleimides based on transition-metal catalysts

Two tandem catalytic systems are described for the synthesis of novel 3,4-disubstituted maleimides using the same Ugi adducts as starting materials. 4-Aryl-3-pyrrolyl- and 4-aryl-3-indolyl-maleimides were successfully obtained via a Pd(OAc)2/PPh3 based protocol. In contrast, maleimide-fused pyrrolo and indolo[1,2-a]quinolines were obtained in a complementary methodology using CuI/L-proline. These strategies involved a combination of benzylic amine oxidation, trans-amidation, intramolecular Knoevenagel condensation, and N-arylation reactions. Computational investigations provide further insights into this reaction sequence.

Developing a straightforward route toward the synthesis of arylaminomaleimides by palladium-catalyzed arylation of one-pot synthesized aminomaleimides

3-Aryl-4-aminomaleimides have well-demonstrated applications, such as being used as fluorophores and inhibitors. However, their previous synthesis methods have involved tedious multi-step procedures or methods that need pre-functionalized maleimides and toxic or unstable reagents. Here, a feasible method is developed to synthesize these useful compounds. This includes the one-pot preparation of 3-aminomaleimides, followed by their direct arylation through a palladium-catalyzed Heck reaction with various aryl iodides regioselectively at the β-position of their amine substituents. The results show that this method efficiently exhibits a broad scope.

Maleimide structure: a promising scaffold for the development of antimicrobial agents

Natural compounds bearing maleimide rings are a series of secondary metabolites derived from fungi/marine microorganisms, which are characterized by a general structure -CO-N(R)-CO-, and the R group is normally substituted with alkyl or aryl groups. Maleimide compounds show various biological activities such as antibacterial, antifungal, and anticancer activity. In this review, the broad-spectrum antimicrobial activities of 15 maleimide compounds from natural sources and 32 artificially synthesized maleimides were summarized, especially against Candida albicans, Sclerotinia sclerotiorum, and Staphylococcus aureus. It highlights that maleimide scaffold has tremendous potential to be utilized in the development of novel antimicrobial agents.

Novel Schiff bases derived from N-aryl maleimide derivatives as an effective antimicrobial agent: Theoretical and experimental approach

A set of new Schiff bases of N-aryl 3- and 4-substituted maleimides has been prepared via condensation of N-aryl 3- and 4- substituted maleimides with p-toluene sulfonyl hydrazide in acidic medium at room temperature. The structures of synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, MS spectral data, and further confirmed by single-crystal x-ray crystallography for 5c. The computational study was carried out using Gaussian 09 software by using the B3LYP/6-311+G(d,p) basis set. Single-crystal study results showed much closeness with computational study results. These novel compounds were screened for their antimicrobial activity against two pathogenic bacteria such as Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC25923) and two pathogenic fungi such as Aspergillus niger (MCIM10231) and Candida albicans (MTCC6275). The investigation of antimicrobial screening data showed that the most of tested compounds are moderate to good microbial inhibitors.

Synthesis and anticancer cytotoxicity with structural context of an α-hydroxyphosphonate based compound library derived from substituted benzaldehydes

We synthesized substituted benzaldehyde derived α-hydroxyphosphonates (αOHP), α-hydroxyphosphonic acids (αOHPA) and α-phosphinoyloxyphosphonates (αOPP) and characterized their cytotoxicity against a panel of cancer cell lines.

Copper-Catalysed Bromoamination of Maleimides using NBS as the Bromine Source

CuBr2-catalysed bromoamination of maleimides has been achieved in THF with alkylamines and N-bromosuccinimide as nitrogen and bromine sources respectively. The reaction conditions were optimised. A series of bromoamination products such as 3-amino-4-bromomaleimides was synthesised with satisfactory yields. Furthermore, a plausible mechanism of the bromoamination of maleimides was discussed.

Base catalysed intermolecular cyclisation of N-protected o-amino benzaldehyde/acetophenone with phosphorus/sulphur based allenes: facile synthesis of substituted quinolines

Base catalyzed reaction of N-Bz protected o-aminobenzaldehyde with allenylphosphonates affords O-phosphorylated quinolines via a route involving a thermal rearrangement.

2,5-Disubstituted 1,3,4-oxadiazole derivatives of chromeno[4,3-b]pyridine: synthesis and study of antimicrobial potency

A convenient synthesis of 1,3,4-oxadiazole containing derivatives of chromeno[4,3-

2-Oxo promoted hydrophosphonylation & aerobic intramolecular nucleophilic displacement reaction

Highly efficient catalyst free methods for the synthesis of α-hydroxy-β-oxo phosphonates (HOP) and α-oxoesters (OE) have been described for the first time. The existence of a 2-oxo group in α-oxoaldehydes (OA) was a key factor in promoting the reaction of the tervalent phosphite form towards activated aldehydes (OA) in the synthesis of HOP.