Post-condensational modifications of the Groebke‐Blackburn‐Bienaymé reaction products for scaffold-oriented synthesis

The Groebke-Blackburn-Bienaymé (GBB) reaction: A powerful tool for generating diverse heterocyclic scaffold libraries in anticancer drug discovery

The Groebke-Blackburn-Bienaymé (GBB) reaction is a versatile multi-component (MCR) synthetic methodology that has transformed anticancer drug discovery by enabling the rapid and efficient generation of diverse heterocyclic scaffolds. These scaffolds, such as imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, and their derivatives, are highly valuable moieties for targeting critical cancer pathways. The modular nature of the GBB reaction, coupled with post-reaction modifications, allows the design of compounds with tailored structures and enhanced pharmacological properties. GBB-derived compounds exhibit broad anticancer potential by modulating diverse molecular targets. These include protein kinases (e.g. Rock2, Gsk3β, B-Raf), microtubule dynamics via tubulin inhibition, and G-quadruplex DNA stabilization in oncogene promoters (e.g., c-MYC, BCL2), disrupting key mechanisms of tumour progression. Moreover, they target epigenetic regulators such as HDACs, CBP/P300 bromodomains, and BET bromodomains, affecting transcriptional regulation and chromatin remodeling. Immune checkpoints (e.g., PD-1/PD-L1), enzymes such as autotaxin, TDP1, and Hsp90, as well as apoptotic regulators (e.g., Bcl-2, BAG3), are also effectively inhibited. More importantly, these compounds address challenging targets, including KRAS G12C mutations and the menin-MLL interaction, offering solutions to previously "undruggable" pathways. The unparalleled efficiency of GBB reaction and its ability to generate structurally diverse, bioactive compounds spanning multiple oncogenic mechanisms highlights its central role in advancing anticancer drug discovery and its transformative impact on therapeutic innovation.

Atroposelective synthesis of axially chiral imidazo[1,2-a]pyridines via asymmetric multicomponent reaction

Imidazo[1,2-a]pyridines are privileged heterocycles with diverse applications in medicinal chemistry; however, the catalytic asymmetric synthesis of these heterocyclic structures remains underexplored. Herein, we present an efficient and modular approach for the atroposelective synthesis of axially chiral imidazo[1,2-a]pyridines via an asymmetric multicomponent reaction. By utilizing a chiral phosphoric acid catalyst, the Groebke-Blackburn-Bienaymé reaction involving various 6-aryl-2-aminopyridines, aldehydes, and isocyanides gave access to a wide range of imidazo[1,2-a]pyridine atropoisomers with high to excellent yields and enantioselectivities. Extensive control experiments underscored the pivotal role of the remote hydrogen bonding donor on the substrates in achieving high stereoselectivity for these reactions. The versatile derivatizations of these atropisomeric products, especially their role as an analog of NOBINs and their facile conversion into unique 6,6-spirocyclic products, further emphasize the merits of this methodology.

Synthesis of Triazolo[4',5':4,5]furo[2,3-c]pyridine via Post Modification of an Unusual Groebke-Blackburn-Bienaymé Multicomponent Reaction

The Groebke-Blackburn-Bienaymé (GBB) reaction is a well-established three-component reaction for synthesizing imidazofused scaffolds from heterocyclic amidines, aldehydes, and isonitriles. However, the replacement of pyridoxal as an aldehyde component in this reaction results in the formation of the furo[2,3-c]pyridine skeleton as an "unusual GBB product". Despite the interesting nature of this unusual reaction, not much work was further reported. The present research investigates the optimization strategy for the synthesis of novel tricyclic triazolo[4',5':4,5]furo[2,3-c]pyridines via diazotization of 2,3-diamino-furo[2,3-c]pyridines specifically synthesized utilizing the chemistry of tert-alkyl isocyanide.

Transition-metal-free intramolecular double hydrofunctionalization of alkyne to access 6/7/5-fused heterocyclic skeletons

We describe a novel intramolecular double hydrofunctionalization cyclization of alkyne with nitrogen and oxygen nucleophilic groups to construct valuable 6/7/5-fused heterocyclic products. This post-Groebke-Blackburn-Bienaymé (GBB) reaction introduces a new class of functionalized isocyanides. Transition-metal-free cyclization, broad substrate scope, and high atom economy were some features of the present protocol.

Trends in the Synthesis of Antimicrobial Derivatives by using the Gewald, Strecker, and Groebke-Blackburn-Bienaymé (GBB) Reactions

BACKGROUND

Multicomponent reactions are highly useful in synthesizing natural products and bioactive molecules. Out of several MCRs, although utilized widely, some remain neglected in review articles. The Gewald and Groebke-Blackburn-Bienaymé (GBB) reactions are two such reactions. This comprehensive review assimilates applications of Gewald and Groebke-Blackburn- Bienayme reactions in synthesizing novel antimicrobial agents. It presents the antimicrobial properties of the synthesized molecules, providing an overview of their potential druggability.

OBJECTIVE

Developing novel antimicrobial agents is the need of the hour. Toward this objective, the scientific community is developing new methods for constructing novel architectures with potential antimicrobial properties. This review will showcase the usefulness of the Gewald, Strecker, and Groebke-Blackburn-Bienaymé (GBB) reactions in synthesizing antimicrobial molecules.

METHODS

The articles are searched by using the Sci-finder search tool and summarize the chemistry of their synthesis and antimicrobial evaluation of the molecules.

RESULTS

This review focuses on synthesizing antimicrobial molecules using the Gewald, Strecker, and Groebke-Blackburn-Bienaymé (GBB) reactions. The antimicrobial activities of the synthesized molecules are also summarized in tables.

CONCLUSION

This review will briefly overview the application of the Gewald, Strecker, and Groebke- Blackburn-Bienaymé (GBB) reactions in synthesizing novel antimicrobial molecules. It contains several molecules with promising activity against resistant and non-resistant microbial strains. These promising molecules could be studied further to develop novel antibiotics.

Synthesis of Imidazo[1,2-a]pyridine-Fused 1,3-Benzodiazepine Derivatives with Anticancer Activity via a One-Pot Cascade GBB-3CR/Pd(II)-Catalyzed Azide-Isocyanide Coupling/Cyclization Process

A new one-pot synthesis of imidazo[1,2-a]pyridine-fused 1,3-benzodiazepine derivatives via a sequential GBB-3CR/Pd(II)-catalyzed azide-isocyanide coupling/cyclization process was developed. The Groebke-Blackburn-Bienaymé three-component reactions (GBB-3CR) of 2-aminopyridine, 2-azidobenzaldehydes, and isocyanides in the presence of a catalytic amount of p-toluenesulfonic acid gave azide intermediates without separation. The reaction was followed by using another molecule of isocyanides to produce imidazo[1,2-a]pyridine-fused 1,3-benzodiazepine derivatives in good yields by the Pd(II)-catalyzed azide-isocyanide coupling/cyclization reaction. The synthetic approach produces novel nitrogen-fused polycyclic heterocycles under mild reaction conditions. The preliminary biological evaluation demonstrated that compound 6a inhibited glioma cells efficiently, suggesting potentially broad applications of the approach for synthesis and medicinal chemistry.