Rh(II)/Pd(0) Dual Catalysis: Interception of Ammonium Ylide with Allyl Palladium to Construct 2,2-Disubstituted Tetrahydroquinoline Derivatives

New synthetic methods to construct 2,2-disubstituted tetrahydroquinoline derivatives are of significant value in pharmaceutical chemistry. Herein, a Rh(II)/Pd(0) dual-catalyzed diazo α-aminoallylation reaction has been developed between allylpalladium(II) and ammonium ylides derived from the Rh₂(OAc)₄-mediated intramolecular N-H bond insertion reaction of diazo compounds, affording various 2,2-disubstituted tetrahydroquinoline derivatives in good yields up to 93% with high chemoselectivities under mild reaction conditions. A substrate scope investigation reveals broad ester substituent tolerance, and control experiments provide the basis for a proposed reaction mechanism.

One-pot synthesis of multi-substituted conjugated dienones by trapping allene carbocations with active ylides

A Rh(II)/boron reagent co-catalyzed unprecedent transformation was established for the rapid construction of multi-substituted conjugated dienones under mild conditions by trapping allene carbocations with oxonium ylides from simple starting points in yields up to 85%. Two CC double bonds, one C-C and one C-O single bond were built in this one-pot reaction. The diversity-oriented strategy was also established to synthesize alkyne ether and dihydrofuran derivatives by a substrate-depended fashion.

Catalytic Approaches to Multicomponent Reactions: A Critical Review and Perspectives on the Roles of Catalysis

In this review, we comprehensively describe catalyzed multicomponent reactions (MCRs) and the multiple roles of catalysis combined with key parameters to perform these transformations. Besides improving yields and shortening reaction times, catalysis is vital to achieving greener protocols and to furthering the MCR field of research. Considering that MCRs typically have two or more possible reaction pathways to explain the transformation, catalysis is essential for selecting a reaction route and avoiding byproduct formation. Key parameters, such as temperature, catalyst amounts and reagent quantities, were analyzed. Solvent effects, which are likely the most neglected topic in MCRs, as well as their combined roles with catalysis, are critically discussed. Stereocontrolled MCRs, rarely observed without the presence of a catalytic system, are also presented and discussed in this review. Perspectives on the use of catalytic systems for improved and greener MCRs are finally presented.

Multicomponent Reactions Involving Diazo Reagents: A 5-Year Update

This review summarizes recent developments in multicomponent reactions of diazo compounds. The role of diazo reagent and the type of interaction between components was analyzed to structure the discussion. In contrast to previous reviews on related topics mostly focused on metal catalyzed transformations, a substantial amount of organocatalytic or catalyst-free methodologies is covered in this work.

FeTPPCl/FeCl3 Co-Catalyzed One-Pot Green Synthesis of α-Diaryl-β-alkynol Derivatives via Propargylic Carbocation Chemistry

A green and highly efficient one-pot method for α-diaryl-β-alkynol derivatives in water at room temperature was developed using the cocatalysis of a Lewis acid and meso-tetraphenylporphyrin iron(III) chloride (FeTPPCl). The unprecedented transformation was promoted by a modulation of the charge properties of propargylic carbocation chemistry and the use of an in situ-generated oxonium ylide as a matching nucleophile. The reaction was performed in water at room temperature with a highly step-economic manipulation in good to excellent yields and with a broad substrate scope. Water also acts as the third reactant for the one-pot transformation. Notably, the FeTPPCl catalyst can be directly reused four times with a slight discount in yields.

Progress in recent development of stereoselective synthesis of β2-amino acid derivatives from β-nitroacrylate derivatives

The synthesis and properties of β-amino acids have drawn considerable attention owing to their ubiquitous presence in naturally occurring products of biological importance. While β3-amino acids can be readily prepared from α-amino acids via one-carbon homologation, the synthesis of β2-amino acids generally requires multistep efforts. This review focuses on the recent advances in the synthesis of β2-amino acids and their derivatives from substituted β-nitropropionate analogues obtained from the stereoselective transformation of β-nitroacrylates.

Recent advances in catalytic enantioselective multicomponent reactions

Multicomponent reactions (MCRs) undoubtedly correspond to one of the synthetic strategies that best fit the new demands of chemistry for presenting high atom economy and enabling molecular diversity. However, many challenges still exist when products possessing stereogenic centres are formed. The field of asymmetric catalytic reactions has achieved significant progress in recent decades; new applications for chiral ligands and catalysts have been demonstrated and new catalysts have been specifically designed for challenging chemical conversions. In this sense, highly efficient approaches for classic multicomponent reactions such as the Ugi reaction and a number of new asymmetric MCRs have been described. In this review we discuss the recent developments that enable catalytic enantioselective MCRs including the proposed mechanistic pathways.

Chemodivergent synthesis of functionalized methanodibenzo[b,f][1,5]diazocin-13-ylmethanones and tetrahydroquinolines via solvent-dependent AB2 and A2B2 multicomponent annulation reactions

A solvent-dependent chemodivergent approach was developed for the synthesis of 6,12-methanodibenzo[b,f][1,5]diazocin-13-ylmethanones and 2,3,4-trisubstituted 1,2,3,4-tetrahydroquinolines involving two distinct AB₂ and A₂B₂ multicomponent processes.