Asymmetric Synthesis oftrans-β-Lactams by a Kinugasa Reaction on Water

Copper-Catalyzed Asymmetric Kinugasa/Michael Addition Cascade Reactions for the Synthesis of Chiral Spiro β-Lactams

A mild copper-catalyzed asymmetric Kinugasa/Michael addition cascade process is developed. The reaction of α, β-unsaturated ester-tethered propiolamides with nitrones provides an efficient protocol for the construction of functionalized chiral 2,6-diazaspiro[3.4]octane-1,5-dione products in satisfactory yields and with high enantio- and diastereoselectivities.

Modular Synthesis of α-Quaternary Chiral β-Lactams by a Synergistic Copper/Palladium-Catalyzed Multicomponent Reaction

An asymmetric multicomponent, interrupted Kinugasa allylic alkylation (IKAA) reaction has been developed with a synergistic Cu-catalyzed Kinugasa system and a Pd-catalyzed allylic alkylation reaction. This unprecedented reaction provides in high yields and with high stereoselectivity a synthesis of α-quaternary chiral β-lactams, which cannot be produced with existing synthetic methods. Stereoselective coupling of two catalytic amounts of transient organometallic intermediates formed in situ is an important feature of this reaction.

Synthetic Organic "Aquachemistry" that Relies on Neither Cosolvents nor Surfactants

There is a growing awareness of the underlying power of catalytic reactions in water that is not limited to innate sustainability alone. Some Type III reactions are catalytically accelerated without dissolution of reactants and are occasionally highly selective, as shown by comparison with the corresponding reactions run in organic solvents or under solvent-free conditions. Such catalysts are highly diversified, including hydrophilic, lipophilic, and even solid catalysts. In this Outlook, we highlight the impressive characteristics of illustrative catalysis that is exerted despite the immiscibility of the substrates and reveal the intrinsic benefits of these enigmatic reactions for synthetic organic chemistry, albeit with many details remaining unclear. We hope that this brief introduction to the expanding field of synthetic organic "aquachemistry" will inspire organic chemists to use the platform to invent new transformations.

An experimental and mechanism study on the regioselective click reaction toward the synthesis of thiazolidinone-triazole

An efficient procedure for the synthesis of novel thiazolidinone triazoles through 32 cycloaddition reactions in the presence of copper(I) species was described, and the molecular mechanism of this 32CA was investigated computationally. Different possible pathways for CA process have been studied to achieve this goal, including one-step pathways for both regioisomers 1,4- and 1,5-triazoles (uncatalyzed, mono-copper, di-copper) and also mono- and di-copper stepwise pathways for 1,4-disubstituted triazole. It was exhibited that the most convenient route in terms of energy barriers includes two copper ions. Based on the calculation, the reaction follows a di-copper stepwise mechanism involving the formation of a six-membered ring and then undergoes a ring contraction to a five-membered ring. The regiochemistry of the reaction was investigated based on local and global reactivity indices of reactants, the transition state stabilities calculation. The electron reorganization along the uncatalyzed one-step mechanism has been investigated by the ELF topological analysis of the bonding changes along with the CA reaction.

1,3-Dipolar cycloaddition of nitrones: synthesis of multisubstituted, diverse range of heterocyclic compounds

The 1,3-dipolar cycloaddition reaction of nitrone is one of the most important methods for the synthesis of different sizes of heterocycles which have enormous applications in natural products, biologically active molecules and pharmaceuticals.

Acenaphtoquinoxaline as a selective fluorescent sensor for Hg (II) detection: experimental and theoretical studies

A new fluorescent chemosensor based on quinoxaline was successfully synthesized through a facile and green catalytic reaction of ortho-phenylenediamine (O-PDA) and acenaphthylene-1,2-dione in the presence of SBA-Pr-SO3H. Prepared a "switch-off" quinoxaline-based receptor to recognized Hg2+ ion in high selectively and, without any interference from other metal ions, was developed. The photophysical behavior of this fluorophore was studied in acetonitrile by using fluorescence spectra. The fluorescence properties of several cations to acenaphtoquinoxaline were investigated in acetonitrile, and the competition test displayed that the probe fluorescence changes were specific for Hg2+ ion. The obtained results have shown high selectivity and sensitivity only for Hg2+. Also, the detection limit was as low as 42 ppb, and a top linear trend was observed between the concentration of Hg2+ ions and fluorescence intensity. The binding stoichiometry between chemosensor L and Hg2+ was found to be 1:1. Moreover, a computational study was performed to obtain an electronic description of the fluorescence emission and quenching mechanisms. The optimized structures and binding mechanisms were supported with a high correlation and agreement by spectroscopy and DFT calculations.

Synthesis of biologically relevant steroidal spiro β-lactams from dienamides through the cascade 4-endo N-cyclization/aerobic oxidation sequence

The steroid nucleus and β-lactam are prevalent in natural products and drug molecules, the compounds containing such fragments always possess diverse and interesting biological profiles. Presented here is an unprecedented cascade 4-endo N-cyclization/aerobic oxidation sequence that enables the synthesis of biologically relevant steroidal spiro β-lactams from dienamides. Of note, two continuous quaternary chiral centers were constructed simultaneously in this process, and the title compounds bearing the OH and CN groups are highly functionalized, allowing for late-stage transformations for construction of diverse compound library. The protocol has several advantages such as mild reaction conditions and short reaction time, therefore could serve as a new strategy for synthesizing β-lactams.

Optimized aqueous Kinugasa reactions for bioorthogonal chemistry applications

Kinugasa reactions hold potential for bioorthogonal chemistry in that the reagents can be biocompatible. Unlike other bioorthogonal reaction products, β-lactams are potentially reactive, which can be useful for synthesizing new biomaterials. A limiting factor for applications consists of slow reaction rates. Herein, we report an optimized aqueous copper(i)-catalyzed alkyne-nitrone cycloaddition involving rearrangement (CuANCR) with rate accelerations made possible by the use of surfactant micelles. We have investigated the factors that accelerate the aqueous CuANCR reaction and demonstrate enhanced modification of a model membrane-associated peptide. We discovered that lipids/surfactants and alkyne structure have a significant impact on the reaction rate, with biological lipids and electron-poor alkynes showing greater reactivity. These new findings have implications for the use of CuANCR for modifying integral membrane proteins as well as live cell labelling and other bioorthogonal applications.

CuFe2O4 nanoparticles catalyze the reaction of alkynes and nitrones for the synthesis of 2-azetidinones

The reaction of alkynes and nitrones (Kinugasa reaction) in the presence of magnetically recoverable CuFe₂O₄ nanoparticles as a highly efficient heterogeneous catalyst under a mild condition for the synthesis of various 2-azetidinones was reported.

Development of TsDPEN based imine-containing ligands for the copper-catalysed asymmetric Kinugasa reaction

A novel class of chiral N,N,N imine-containing ligands derived from TsDPEN (N-(p-tosyl)-1,2-diphenylethylene-1,2-diamine) has been developed and applied to the copper-catalyzed asymmetric Kinugasa reaction. The copper(ii) salt proved to be an efficient catalyst precursor, and it provides an efficient way to synthesize enantioenriched cis-β-lactam. The pathway is air-tolerant and easily manipulated, and the ligands are easy to synthesize. A working model is proposed in which the stereocontrolling step is the [2 + 2] cycloaddition between ketene and imine to explain the observed stereoselectivities.

A novel class of chiral N,N,N imine-containing ligands derived from TsDPEN has been developed and applied to the copper-catalyzed asymmetric Kinugasa reaction.

Asymmetric Synthesis of α-Alkylidene-β-Lactams through Copper Catalysis with a Prolinol-Phosphine Chiral Ligand

A copper/prolinol-phosphine chiral catalyst enabled the one-step synthesis of chiral α-alkylidene-β-lactams. Optimization of the chiral ligand for steric and electronic properties realized the highly enantioselective coupling of nitrones and propargyl alcohol derived alkynes. The resulting chiral α-alkylidene-β-lactams served as a platform for various β-lactams via well-established transformations of α,β-unsaturated carbonyl compounds.

Catalytic Organic Reactions in Water toward Sustainable Society

Traditional organic synthesis relies heavily on organic solvents for a multitude of tasks, including dissolving the components and facilitating chemical reactions, because many reagents and reactive species are incompatible or immiscible with water. Given that they are used in vast quantities as compared to reactants, solvents have been the focus of environmental concerns. Along with reducing the environmental impact of organic synthesis, the use of water as a reaction medium also benefits chemical processes by simplifying operations, allowing mild reaction conditions, and sometimes delivering unforeseen reactivities and selectivities. After the "watershed" in organic synthesis revealed the importance of water, the development of water-compatible catalysts has flourished, triggering a quantum leap in water-centered organic synthesis. Given that organic compounds are typically practically insoluble in water, simple extractive workup can readily separate a water-soluble homogeneous catalyst as an aqueous solution from a product that is soluble in organic solvents. In contrast, the use of heterogeneous catalysts facilitates catalyst recycling by allowing simple centrifugation and filtration methods to be used. This Review addresses advances over the past decade in catalytic reactions using water as a reaction medium.

Asymmetric Synthesis of β-Lactams through Copper-Catalyzed Alkyne-Nitrone Coupling with a Prolinol-Phosphine Chiral Ligand

Prolinol-phosphine chiral ligands enabled highly enantioselective copper-catalyzed intermolecular alkyne-nitrone coupling (Kinugasa reaction) to produce 1,3,4-trisubstituted chiral β-lactams. A high level of enantiocontrol was achieved not only with aryl- or alkenylacetylenes but also with alkylacetylenes, which were important but unfavorable substrates in the previously reported protocols. Two-point hydrogen bonding between the chiral ligand and the nitrone oxyanion consisting of O-H⋅⋅⋅O and C(sp³ )-H⋅⋅⋅O hydrogen bonds is proposed.

Organic synthesis reactions on-water at the organic–liquid water interface

Organic synthesis on-water has shown surprising successful synthetic methods. This review discusses the array of chemistry, which has been adapted with this methodology.

Kinugasa reactions in water: from green chemistry to bioorthogonal labelling

The Kinugasa reaction has become an efficient method for the direct synthesis of β-lactams from substituted nitrones and copper(I) acetylides. In recent years, the reaction scope has been expanded to include the use of water as the solvent, and with micelle-promoted [3+2] cycloadditions followed by rearrangement furnishing high yields of β-lactams. The high yields of stable products under aqueous conditions render the modified Kinugasa reaction amenable to metabolic labelling and bioorthogonal applications. Herein, the development of methods for use of the Kinugasa reaction in aqueous media is reviewed, with emphasis on its potential use as a bioorthogonal coupling strategy.

Enantioselective cis-β-lactam synthesis by intramolecular C-H functionalization from enoldiazoacetamides and derivative donor-acceptor cyclopropenes

β-Lactam derivatives are produced through donor–acceptor cyclopropene intermediates in high yield with exclusive cis-diastereoselectivity, and high enantiocontrol.

β-Lactam derivatives are produced through intermediate donor–acceptor cyclopropene intermediates in high yield, exclusive cis-diastereoselectivity, and high enantiocontrol in a chiral dirhodium carboxylate catalyzed intramolecular C–H functionalization reaction of enoldiazoacetamides.