An Ylide Transformation of Rhodium(I) Carbene: Enantioselective Three-Component Reaction through Trapping of Rhodium(I)-Associated Ammonium Ylides by β-Nitroacrylates

Imine Directed Cp*RhIII -Catalyzed N-H Functionalization and Annulation with Amino Amides, Aldehydes, and Diazo Compounds

A multicomponent annulation that proceeds by imine directed Cp*RhIII -catalyzed N-H functionalization is disclosed. The transformation affords piperazinones displaying a range of functionality and is the first example of transition metal-catalyzed multicomponent N-H functionalization. A broad range of readily available α-amino amides, including those derived from glycine, α-substituted, and α,α-disubstituted amino acids, were effective inputs and enabled the incorporation of a variety of amino acid side chains with minimal racemization. Branched and unbranched alkyl aldehydes and various stabilized diazo compounds were also efficient reactants. The piperazinone products were further modified through efficient transformations. Mechanistic studies, including X-ray crystallographic characterization of a catalytically competent five-membered rhodacycle with imine and amide nitrogen chelation, provide support for the proposed mechanism.

Interplay of Polarity and Confinement in Asymmetric Catalysis with Chiral Rh Diene Complexes in Microemulsions

Microemulsions provide a unique opportunity to tailor the polarity and liquid confinement in asymmetric catalysis via nanoscale polar and nonpolar domains separated by a surfactant film. For chiral diene Rh complexes, the influence of counterion and surfactant film on the catalytic activity and enantioselectivity remained elusive. To explore this issue chiral norbornadiene Rh(X) complexes (X=OTf, OTs, OAc, PO₂F₂) were synthesized and characterized by X‐ray crystallography and theoretical calculations. These complexes were used in Rh‐catalyzed 1,2‐additions of phenylboroxine to N‐tosylimine in microemulsions stabilized either exclusively by n‐octyl‐β‐D‐glucopyranoside (C₈G₁) or a C₈G₁‐film doped with anionic or cationic surfactants (AOT, SDS and DTAB). The Rh(OAc) complex showed the largest dependence on the composition of the microemulsion, yielding up to 59 % (90 %ee) for the surfactant film doped with 5 wt% of AOT as compared to 52 % (58 %ee) for neat C₈G₁ at constant surfactant concentration. Larger domains, determined by SAXS analysis, enabled further increase in yield and selectivity while the reaction rate almost remained constant according to kinetic studies.

Three-Component Reaction for the Synthesis of Highly Functionalized Propargyl Ethers

Multicomponent reactions provide efficient means to access molecular complexity. Herein, we report a copper-catalyzed three-component reaction of diazo compounds, alcohols and ethynyl benziodoxole (EBX) reagents for the synthesis of propargyl ethers. Extensive variations of the three partners of the reaction is possible, leading to highly functionalized and structurally diverse products under mild conditions. Alkynylation of a copper ylide intermediate is postulated as key step for this transformation.

Rapid Synthesis of N-Tosylhydrazones under Solvent-Free Conditions and Their Potential Application Against Human Triple-Negative Breast Cancer

Some N-tosylhydrazone derivatives were effectively synthesized under solvent-free conditions by using a grinding method at room temperature. The short reaction time, clean and mild process with simple workup and easy purification of the target compounds were salient features of the present protocol, which enables straightforward access to N-tosylhydrazones. Among the tosylhydrazone derivatives evaluated, compound 3 l exhibits excellent apoptosis-promoting and anticancer potential against triple-negative breast cancer (TNBC) cell lines. This research shows that our synthesized compound 3 l may be a desirable and effective therapeutic drug against TNBC.

Rhodium(I)-Catalyzed Coupling-Cyclization of C═O Bonds with α-Diazoketones

An unprecedented intermolecular nucleophilic attack of C═X bonds (X = O and S) on the rhodium(I)-carbenes has been developed. This transformation allows for the coupling-cyclization of aroylamides with α-diazoketones and provides concise access to 2,4,5-trisubstituted 1,3-oxazoles and 1,3-thiazoles with a broad tolerance of functional groups.

Metal-Free Geminal Difunctionalization of Diazocarbonyl Compounds: A One-Pot Multicomponent Strategy for the Construction of α,β-Diamino Carbonyl Derivatives

An unprecedented three-component domino oxidative coupling of diazocompounds for the efficient synthesis of α-azido-β-amino esters with non-activated dimethylamino compounds and simple TMSN₃ was achieved. The main features of this method include metal-free catalysis, satisfactory functional group tolerance, general applicability in complex molecule architectures, and excellent diastereoselectivity in the presence of chiral auxiliaries. In addition, several related control experiments have been conducted to investigate the reaction mechanism.

Enantioselective Rhodium(I) Donor Carbenoid-Mediated Cascade Triggered by a Base-Free Decomposition of Arylsulfonyl Hydrazones

The reaction of diyne arylsulfonyl hydrazone substrates under rhodium(I)/BINAP catalysis gives access to sulfonated azacyclic frameworks in a highly enantioselective manner. This new cascade process considerably increases the molecular complexity by generating two C-C bonds, one C-S bond, and one C-H bond. Theoretical calculations, competitive experiments, and deuterium labeling have jointly been used to propose a mechanism that accounts for the reaction. The mechanism involves the formation of vinyl rhodium carbenoids, hydride migratory insertion, and intermolecular stereoselective nucleophilic attack. The last two steps are the key to the stereoselectivity of the process.

Rhodium(I)-catalyzed asymmetric carbene insertion into B-H bonds: highly enantioselective access to functionalized organoboranes

A unique rhodium(I)-catalyzed asymmetric B-H insertion of α-diazo carbonyl compounds with easily available amine-borane adducts was achieved using a newly developed C1-symmetric chiral diene as ligand. This first Rh(I)-carbene-directed B-H insertion example represents an attractive and promising approach for synthesis of highly enantioenriched organoboron compounds, allowing for the efficient construction of α-boryl esters and ketones with excellent enantioselectivities (up to 99% ee) under exceptionally mild conditions.