An Overview of Rhodium‐Catalysed Multi‐Component Reactions

Cobalt-Catalyzed Diester Formation with CO at Atmospheric Pressure via Three-Component Reactions

We propose a cobalt-catalyzed three-component reaction conducted under mild conditions. Following the carbonyl insertion at atmospheric pressure, the reaction proceeds via a nucleophilic attack by alcohols to form diesters. Notably, the scope of nucleophilic reagents can be extended to include a range of anilines. Furthermore, the products of this transformation serve as crucial synthetic building blocks for diverse organic synthesis processes, with subsequent derivatizations yielding promising results.

Divergent Geminal Alkynylation-Allylation and Acylation-Allylation of Carbenes: Evolution and Roles of Two Transition-Metal Catalysts

Cooperative bimetallic catalysis to access novel reactivities is a powerful strategy for reaction development in transition-metal-catalyzed chemistry. Particularly, elucidation of the evolution of two transition-metal catalysts and understanding their roles in dual catalysis are among the most fundamental goals for bimetallic catalysis. Herein, a novel three-component reaction of a terminal alkyne, a diazo ester, and an allylic carbonate was successfully developed via cooperative Cu/Rh catalysis with Xantphos as the ligand, providing a highly efficient strategy to access 1,5-enynes with an all-carbon quaternary center that can be used as immediate synthetic precursors for complex cyclic molecules. Notably, a Meyer-Schuster rearrangement was involved in the reactions using propargylic alcohols, resulting in an unprecedented acylation-allylation of carbenes. Mechanistic studies suggested that in the course of the reaction Cu(I) species might aggregate to some types of Cu clusters and nanoparticles (NPs), while the Rh(II)2 precursor can dissociate to mono-Rh species, wherein Cu NPs are proposed to be responsible for the alkynylation of carbenes and work in cooperation with Xantphos-coordinated dirhodium(II) or Rh(I)-catalyzed allylic alkylation.

Rh(II)/Pd(0) Dual-Catalyzed Regio-Divergent Three-Component Propargylic Substitution

Regio-divergent propargylic substitution to generate functionally diverse products from identical starting materials remains a formidable challenge, probably due to the unpredictable regiochemical complexity. In practically, the synthesis of α-quaternary propargylic-substituted products is still much less developed, and preprepared nucleophiles are generally applied in this type of reaction with propargylic substrates, which limits the reaction efficiency and diversity of the obtained products. Herein, we disclose unprecedented three-component propargylic substitution of α-diazo esters with amines and propargylic carbonates under dirhodium/palladium dual catalysis. The key to the success of this multicomponent propargylic substitution is to avoid two-component side reactions through a tandem process of dirhodium(II)-catalyzed carbene insertion and palladium-catalyzed regiodivergent propargylic substitution. The judicious selection of a diphosphine (dppf) or monophosphine (tBuBrettphos) as the ligand is crucial for the reaction to generate different products in a switchable way, α-quaternary 1,3-dienyl or propargylated products, with high regio- and chemoselectivities.

Synthesis and characterization of Co-MOF@Ag2O nanocomposite and its application as a nano-organic catalyst for one-pot synthesis of pyrazolopyranopyrimidines

In this study, a Co-MOF was synthesized via a co-precipitation procedure and then used as support for stabilizing Ag ions and producing Co-MOF@Ag2O nanocomposite by microwave irradiation. The characterization of synthesized Co-MOF@Ag2O nanocomposite was performed by using different techniques such as field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analyses, X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) and Fourier-transform infrared (FT-IR). The prepared Co-MOF@Ag2O nanocomposite was applied as a heterogeneous nano-catalyst in the synthesis of pyrazolopyranopyrimidines in water at 50 °C via the one-pot multicomponent reaction of ethyl acetoacetate, hydrazine hydrate, aromatic aldehydes and barbituric acid derivatives. Through this straightforward and effective protocol, different tricyclic fused pyrazolopyranopyrimidines were synthesized at high yields, and short reaction times, through an uncomplicated work-up process with no by-product. The Co-MOF@Ag2O nanocomposite has been effectively recycled for four consecutive cycles without appreciable loss in its activity. Cost-effectiveness, no need for column chromatography, mild conditions, catalyst recyclability, and eco-friendly nature make it a promising candidate compared to other methods.

Dirhodium(II)/Xantphos-Catalyzed Relay Carbene Insertion and Allylic Alkylation Process: Reaction Development and Mechanistic Insights

Although dirhodium-catalyzed multicomponent reactions of diazo compounds, nucleophiles and electrophiles have achieved great advance in organic synthesis, the introduction of allylic moiety as the third component via allylic metal intermediate remains a formidable challenge in this area. Herein, an attractive three-component reaction of readily accessible amines, diazo compounds, and allylic compounds enabled by a novel dirhodium(II)/Xantphos catalysis is disclosed, affording various architecturally complex and functionally diverse α-quaternary α-amino acid derivatives in good yields with high atom and step economy. Mechanistic studies indicate that the transformation is achieved through a relay dirhodium(II)-catalyzed carbene insertion and allylic alkylation process, in which the catalytic properties of dirhodium are effectively modified by the coordination with Xantphos, leading to good activity in the catalytic allylic alkylation process.

Magnetization of biochar nanoparticles as a novel support for fabrication of organo nickel as a selective, reusable and magnetic nanocatalyst in organic reactions

Waste recycling is important process in green chemistry and economic efficiency. Herein, magnetized biochar nanoparticles were modified under green and environmentally friendly method and further were applied as reusable catalyst in organic reactions.