Gold-catalyzed post-MCR transformations towards complex (poly)heterocycles

Electrochemical Post-Ugi Cyclization for the Synthesis of Highly Functionalized Spirolactams

The combination of the Ugi reaction and electro-organic synthesis can aid in the creation of novel heterocycles that have not been previously explored. In this study, a new strategy utilizing bis-amides from the Ugi reaction has been developed, which can produce C-S, C-Se, and C-C═O functionalized five-membered spirolactams mediated by electricity under catalyst- and metal-free conditions. Notably, this approach can be applied using a microelectro-flow reactor (μ-EFR) for gram-scale synthesis. The described strategy can synthesize complex azaspiro-fused tricyclic scaffolds with high diastereo- and regioselectivity, highlighting its versatility and potential.

A DFT Study on Gold-Catalyzed Domino Cyclization for Post-Ugi Synthesis of Spiroindolines: Insights on the Origin of Remarkable Diastereoselectivity

We report a comprehensive DFT study on gold-catalyzed domino cyclization to spiroindolines. The diastereoselectivity was analyzed based on the established coordination spheres. These computational results not only explain the origin...

Access to Polycyclic Azepino[5,4,3-cd]indoles via a Gold-Catalyzed Post-Ugi Dearomatization Cascade

The development of a rapid and diverse access to complex natural product-like 3,4-fused indole scaffolds has always attracted considerable attention from synthetic and medicinal communities. We herein disclose a modular and straightforward protocol to prepare the densely substituted polycyclic azepino[5,4,3-cd]indole scaffolds. This synthetic process involves an Ugi four-component reaction from easily available starting materials and a gold-catalyzed post-Ugi domino dearomatization/Michael addition sequence, enabling facile access to the highly functionalized azepino[5,4,3-cd]indole core with excellent chemo-, regio-, and diastereoselectivity.

Sequential and direct multicomponent reaction (MCR)-based dearomatization strategies

Dearomatization strategies in a multicomponent fashion often result in complex heterocyclic frameworks, which have attracted the attention of chemists due to their natural product-like structures. The combination of these two processes can easily achieve extended molecular complexity and diversity from simple starting materials with high atom economy. Thus, this field has attracted extensive interest owing to its potential significance in both asymmetric catalysis and convenient build-up of libraries of molecules with novel three-dimensional scaffolds, which may find application in medicinal chemistry. Accordingly, a systematic review on this topic will provide the synthetic organic community with a conceptual overview and comprehensive understanding of the different multicomponent reaction (MCR) cascades involving dearomatization as the characteristic step. In addition, this review will help researchers to look at this promising area from a different perspective with respect to drug discovery, new MCR-based disconnections and often hidden opportunities.

Dienaminodioate based multicomponent reactions with post-benzylic oxidative transformations mediated by DDQ

Multicomponent reactions (MCRs) using dienaminodioate with post-benzylic oxidative transformation mediated by DDQ that afforded a diverse array of products are described. An unprecedented rearrangement of 1,2-dihydropyridines (1,2-DHPs), 3CR products, to 2-pyridones in good yields with a broad substrate scope by DDQ-mediated benzylic oxidation via a pyridinium intermediate is reported. Treatment of the pyridinium intermediate with tert-butyl isocyanide afforded isomerized 1,2-DHPs, analogous to Ritter amides. Further diversification using 3CR products bearing a benzylic group, predictably, promoted the synthesis of 2-pyridone with a benzylideneamine group and a benzo[d]oxazole appended biaryl group by DDQ. A formal 1,6-reduction product from 2-pyridone in the presence of NaBH4 is also observed.

Gold-catalyzed domino cyclization enabling construction of diverse fused azaspiro tetracyclic scaffolds: a cascade catalysis mechanism due to a substrate and counterion

The detailed mechanism and origins of gold-catalyzed domino cyclization to diverse fused azaspiro tetracyclic scaffolds by cooperative dual catalysis and cascade catalysis are systematically studied.