Rh catalyzed multicomponent tandem and one-pot reactions under hydroformylation conditions

Recent development towards alkene hydroformylation catalysts integrating traditional homo- and heterogeneous catalysis

This mini-review provides the recent progress towards catalysts for the hydroformylation of catalysts that bridge traditional homo- and heterogeneous catalysis, highlighting the future development of heterogeneous catalysts in hydroformylation.

Immobilization of Rh(I)-N-Xantphos and Fe(II)-C-Scorpionate onto Magnetic Nanoparticles: Reusable Catalytic System for Sequential Hydroformylation/Acetalization

Two heterogeneous catalysts, MNP@SiO2-N-Xantphos/Rh(I) and MNP@SiO2-NH-C-scorpionate/Fe(II), were prepared by reaction of chloro-functionalized MNP@SiO2 with N-Xantphos and amino-functionalized MNP@SiO2 with iron(II)/C-allyl-scorpionate through nucleophilic substitution and hydroaminomethylation reactions, respectively. All catalysts were characterized using standard spectroscopic means, transmission electron microscopy (TEM), thermogravimetry (TG), and inductively coupled plasma optical emission spectrometry (ICP-OES). An active and highly selective one-pot hydroformylation/acetalization homogeneous system for the transformation of terminal and highly substituted olefins (including terpenes) onto ethyl acetals is described. A synergic effect of bimetallic Rh(I)/P and Fe(II)/C-scorpionate catalysts is disclosed for the first time. The further sequential use of the heterogeneous catalysts, MNP@SiO2-N-Xantphos/Rh(I) and MNP@SiO2-NH-C-scorpionate/Fe(II) in hydroformylation/acetalization reactions allows the direct transformation of olefin onto ethyl acetals, keeping the activity and selectivity. Both catalysts were easily recovered by magnetic separation and reused with negligible loss of activity/selectivity, after six reutilization cycles.

The first one-pot metathesis–hydroformylation procedure: a straight synthesis of 2-arylpropanals from renewable 1-propenylbenzenes

2-Arylpropanals are synthesised from renewable 1-propenylbenzenes via a two-step, one-pot procedure.

Copper-catalyzed direct amination of benzylic hydrocarbons and inactive aliphatic alkanes with arylamines

A new synthetic method toward direct C-N bond formation through saturated C-H amination of benzylic hydrocarbons and inactive aliphatic alkanes with primary aromatic amines under an inexpensive catalyst/oxidant (Cu/DTBP) system has been developed. Both aminopyridines and anilines could react smoothly with primary and secondary benzylic C-H substrates or cyclohexane to form the corresponding aromatic secondary amines in moderate to good yields. This protocol has the advantages of wide functional group tolerance and use of readily available raw materials.

Assembly of Tetrahydropyran Derivatives from Aldehydes, Allylboronates, and Syngas by Asymmetric Relay Catalytic Cascade Reaction

An efficient synthesis of highly enantio-enriched tetrahydropyrans from readily available aldehydes, allylboronates, and syngas has been established by multiply relay catalysis of rhodium and chiral phosphoric acid. The cascade reaction integrates the asymmetric allylboration of aldehydes and alkene hydroformylation, providing a structurally diverse range of products with different workup procedures. The concise synthesis of key chiral building blocks to access herboxidiene and leucascandrolide A demonstrates the high synthetic utility of this method. The cascade reaction employing alkenes to replace aldehydes was also successful.

Featuring Xantphos

This review highlights the use of the bisphosphine ligand group in homogeneous catalysis.

Rh nanoparticles from thiolate dimers: selective and reusable hydrogenation catalysts in ionic liquids

Thiolate-capped RhNPs in imidazolium-based ionic liquids were synthesized from [Rh(μ-SR)(COD)]₂ dimmers under H₂ pressure without external addition of ligand stabilizers, preserving thiolate integrity on the nanoparticle surface. This nanoparticulated systems showed a remarkable selectivity that led to their application in the one pot reductive N-alkylation to produce amines.

A Metal-Free Regioselective Multicomponent Approach for the Synthesis of Free Radical Scavenging Pyrimido-Fused Indazoles and Their Fluorescence Studies

This study deals with a new and efficient metal-free regioselective synthesis of pyrimido-fused indazoles with nitrogen ring junction motifs. We have developed a metal-free domino type reaction between 3-aminoindazole, aryl aldehydes and aceotophenones in the presence of KOH/DMF that leads to pyrimido[1,2-b]indazole analogues. Response Surface Methodology (RSM) coupled with a Box-Behnken design (BBD) were utilized for exploring the effect of base used (A), temperature of reaction (B) and (C), reaction time. This approach can allow access to a variety of pyrimidoindazole fluorophores and related compounds. The compound N,N-dimethyl-4-(2-phenylpyrimido[1,2-b]indazol-4-yl)aniline (4e) displays the maximum fluorescence intensity at 518 nm and shows a fluorescence quantum yield of 0.068. The synthesized pyramido-fused indazoles have been evaluated for their free radical scavenging activity and compound 4f showed good antioxidant activity.

Homogeneous rhodium(i)-catalysis in de novo heterocycle syntheses

Rh(i)-catalysed reactions often employ mild reaction conditions and offer excellent functional group tolerance, making them ideal transformations for the preparation of complex molecules. This review surveys examples of these synthetically useful transformations as applied to the synthesis of various heterocycles.