Asian Journal of Organic Chemistry最新文献

The direct reductive amination of aldehydes and ketones with primary/secondary amines is the primary approach to the synthesis of substituted secondary and tertiary amines. Generally, an external reducing agent or a hydride source is required for this transformation. However, in the recent past, many efforts have been made to perform this transformation without the need for any external hydride sources. However, most of those protocols involve harsh conditions (very high temperature or the use of microwave). In this article, we demonstrate that one of the tris(aryl)cyclopropenium salts could be used as an organic Lewis acid catalyst for the reductive amination of aryl aldehydes with indolines without the use of any external hydride source. Basically, the cyclopropenium cation (as a Lewis acid) activates the carbonyl group of the aldehyde, and the reaction proceeds through the formation of the iminium ion followed by a hydride shift from the α-carbon of another indoline to generate the desired amine. Unlike the other reported methods (without an external hydrogen source), this protocol worked well under milder conditions and many aryl aldehydes underwent reductive amination with indolines to provide the respective N-benzyl indoline derivatives in moderate to good yields.

The increasing occurrence of algal blooms in aquatic ecosystems has heightened interest in bacillamide alkaloids owing to their pronounced algicidal activity. A critical review of the literature revealed several inconsistencies and contradictions regarding the absolute configurations and optical rotations of both naturally occurring and synthetically prepared bacillamides. To clarify these discrepancies, we developed a new enantioselective synthesis of bacillamides B–D, neobacillamide A, and their respective antipodes, starting from the enantiomers of 2-(1-hydroxyethyl)thiazole. This approach enables the efficient and stereocontrolled preparation of all target compounds, along with their enantiomers. Importantly, single-crystal X-ray diffraction analysis of the picrate salt of (–)-bacillamide D and its antipode in conjunction with their synthetic relationships, allowed an unambiguous assignment of absolute configuration. The absolute configurations and directions of optical rotation were reliably established for the entire series of bacillamides and their enantiomers. Chiral HPLC methods were also developed to determine the enantiomeric excess of the alkaloids and their counterparts. Our results correct previous stereochemical misassignments and establish a definitive correlation between structure, chirality, and optical rotation for this class of bioactive natural products. The clarified stereochemical framework provides a solid foundation for understanding structure–activity relationships and for the rational design of analogues with enhanced biological efficacy.

1,1-Dibromoalk-1-enes are a pivotal class of organic synthons and occupy an outstandingly important role in both academic and industrial communities due to their accessibility and commercial availability. The development of novel, powerful, and highly efficient strategy that employed those cost-effective reagents for the selective assembly of a great deal of structurally diverse elaborated molecular architectures has attracted considerable interest in organic synthesis, medicinal chemistry, and materials science. Over the past few decades, a resurgence of interest regarding 1,1-dibromoalk-1-enes has been witnessed, and substantial research efforts have been dedicated to investigating their reactivity and synthetic applications, with primary focus on developing efficient methodologies for constructing structurally diverse heterocyclic frameworks. In this regard, numerous reaction strategies featuring high reactivity, operational simplicity, and excellent atom economy have been systematically explored, thereby expanding the synthetic utility of 1,1-dibromoalk-1-enes in modern organic chemistry. This review summarizes the development of 1,1-dibromoalk-1-enes through different types of reactions, which could be classified into the following categories: (1) 1,1-dibromoalk-1-ene as alkenylation reagent; (2) 1,1-dibromoalk-1-ene as alkynylation reagent; (3) cyclization reaction of 1,1-dibromoalk-1-enes; and (4) other types of reactions of 1,1-dibromoalk-1-ene.

Enamides are important intermediates in organic synthesis, and the desaturation of amides represents an efficient and versatile approach for the synthesis of enamides. Recently, increasing efforts have been made to develop more efficient and sustainable methods for the desaturation of amide under different conditions. In this review, we summarized the most recent advances in the desaturation of amide, including transition-metal-catalyzed oxidative desaturation, transition-metal-free oxidative desaturation, photoinduced redox desaturation, and electrochemical anodic oxidative desaturation. The substrate scope and mechanistic details were also discussed.

Catenanes, an intriguing class of mechanically interlocked molecules (MIMs), have garnered substantial attention due to their dynamic redox-responsive behaviors and unique topological architectures. The interlocked nature of these systems allows precise control of molecular motion under electrochemical stimuli, which is valuable in designing molecular machines and devices. This review highlights contemporary advancements in the structural modification of catenanes to fine-tune their redox properties. Emphasis is placed on how changes in substitution patterns, coordination environments, and macrocyclic components curb redox behavior and facilitate reversible molecular switching. By integrating insights from both metal-containing and metal-free systems, we outline strategies for developing responsive catenane architectures with potential applications in molecular electronics, sensors, and nanomechanical devices.

A [3 + 2] cycloaddition reaction between the in situ generated azaoxyallyl cations and Weinreb amides provided an efficient approach to access 2-amino-4-Oxazolidinones. Electrophilicity of the carbonyl group in Weinreb amide leveraged such a reaction, which is otherwise elusive with regular amides. The reaction proceeds smoothly at room temperature with the aid of HFIP as a promoter. Lability of the C2 amino group under dilute HFIP was exploited to expand the chemical space at the C2 position with different nucleophiles.

A Lewis acid–promoted intermolecular Friedel–Crafts acylation/cyclization reaction of 2-methoxybenzoyl chlorides with 1-haloalkynes has been developed to access various 3-halo(thio)chromenones. This one-pot methodology features mild reaction conditions, operational simplicity, and broad substrate scope, tolerating various diversely decorated 1-haloalkynes and 2-methoxybenzoyl chlorides. Gram-scale experiments and late-stage modifications, including Cu-catalyzed heterocycle formation and Pd-catalyzed Suzuki-Miyaura coupling, further highlight the potential synthetic practicality of this protocol. This work offers a straightforward and versatile approach to synthesize 3-halo(thio)chromenones.

A copper(I)-catalyzed four-component interrupted click/amination cascade reaction for the efficient synthesis of various 5-amino-1,2,3-triazoles has been developed. The key step in this reaction is the interception of the in situ-formed cuprate-triazole intermediate with O-benzoylhydroxylamine. This four-component reaction proceeds under mild conditions with complete regioselectivity. It's also characterized by a broad substrate scope and good functional group tolerance.

Mesoionic carbenes (MICs) exhibit stronger σ-donating and weaker π-accepting properties compared to classical N-heterocyclic carbenes (NHCs), positioning their Breslow enolates as super electron donors for single-electron transfer (SET) processes. This work evaluates the reducibility of Breslow enolates (BI−s) derived from MICs by synthesizing a series of 4-acyl-1,2,3-triazoliums with diverse substituents and analyzing their electrochemical properties via cyclic voltammetry. Substituents exerted significant influence on reduction potentials, with electron-donating groups lowering potentials and electron-withdrawing groups elevating them. Substituent position further modulated reducibility, as electron-withdrawing esters increased potential by reducing electron density. Alkali metal cations (Li⁺, Na⁺, K⁺) can also alter the redox potential and reversibility. The electrochemical data provide a foundation for designing MIC-catalyzed SET reactions, expanding synthetic applications in radical-mediated transformations and photocatalysis. This work bridges gaps in understanding MIC redox behavior, enabling targeted reaction design for diverse carbon–carbon bond-forming processes.