An Efficient Nickel-Catalyzed Asymmetric Oxazole-Forming Ugi-Type Reaction for the Synthesis of Chiral Aryl-Substituted THIQ Rings

Cascade Reaction of Tryptamine-Derived Isocyanides with Nitrile Oxides: Construction of Oxazine Fused-Spiroindoline Derivatives

A one-step cascade reaction of tryptamine-derived isocyanides with in situ generated nitrile oxides for the synthesis of fused spiroindolines was described. The desired products could be efficiently synthesized in moderate to good yields (42-87%). The protocol features mild conditions, wide substrate scope, and high efficiency.

LFZ-4-46, a tetrahydroisoquinoline derivative, induces apoptosis and cell cycle arrest via induction of DNA damage and activation of MAPKs pathway in cancer cells

LFZ-4-46, that is [2-hydroxy-1-phenyl-1,5,6,10b-tetrahydropyrazolo(5,1-a) isoquinolin-3(2H)-yl](phenyl) methanone, a tetrahydroisoquinoline derivative with a pyrazolidine moiety, was synthetically prepared. The anti-cancer mechanism of the compound has not been clarified yet. In this study, the anticancer effects and potential mechanisms of LFZ-4-46 on human breast and prostate cancer cells were explored. (a) 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoliumbromide assay was first performed to detect the effects of LFZ-4-46 on the viability of human cancer cells. (b) Comet assay was utilized to evaluate DNA damage. (c) Cell cycle, apoptosis and mitochondrial membrane potential were detected by flow cytometry. (d) The expression of relative proteins was detected by western blotting assay. LFZ-4-46 significantly inhibited the viability of cancer cells in a time- and dose-dependent manner and had no obviously inhibitory effect on the viability of mammary epithelial MCF-10A cells. Mechanistic studies demonstrated that LFZ-4-46-induced cell apoptosis and cycle arrest were mediated by DNA damage. It caused DNA damage through activating γ-H2AX and breaking DNA strands. Further studies showed that mitogen-activated protein kinasess pathway was involved in these activated several key molecular events. Finally, LFZ-4-46 showed a potent antitumor effect in vivo. These results suggest that LFZ-4-46 may be a potential lead compound for the treatment of breast and prostate cancer.

Brønsted Acid Organocatalyzed Three-Component Hydroamidation Reactions of Vinyl Ethers

Hydroamidation of carbon-carbon double bonds is an attractive strategy for installing nitrogen functionality into molecular scaffolds and, with it, increasing molecular complexity. To date, metal-based approaches have dominated this area of chemical synthesis, despite the drawbacks of air and moisture sensitivity, limited functional group tolerance, toxicity, and/or high cost often associated with using metals. Here, in offering an alternative solution, we disclose an operationally simple, metal-free, one-pot, regioselective, multicomponent synthetic procedure for the hydroamidation of carbon-carbon double bonds. This method features mild reaction conditions and utilizes isocyanides and vinyl ethers for the rapid and modular synthesis of privileged α-oxygenated amide scaffolds. In unraveling the mechanistic underpinning of this non-metal-based reactivity, we present kinetic solvent isotope effect studies, variable time normalization analysis, and density functional theory computations offering insight into the mechanism of this multistep catalytic hydroamidation process.

An overview of the reactions involving azomethine imines over half a decade

Azomethine imines constitute a versatile class of 1,3-dipoles which was used extensively for biologically relevant N-heterocycle synthesis – a five-year recap.

Synthesis of strained 1,2-diazetidines via [3 + 1] cycloaddition of C,N-cyclic azomethine imines with isocyanides and synthetic derivation

Strained diazetidines are assembled simply from 1,3-dipolar cycloaddition of isocyanides and C,N-cyclic azomethine imines, and their diversified transformations are presented.

Cyclic Imines in Ugi and Ugi-Type Reactions

Ugi four-component reactions (U-4CRs) are widely recognized as being highly efficient for the synthesis of pseudopeptides. However, the products of these reactions are not so interesting as drug candidates because they are not conformationally restricted enough for a potent interaction with biological targets. One possible way to overcome this problem is to replace amine and oxo components in the U-4CRs with cyclic imines in so-called Joullié-Ugi three-component reactions (JU-3CRs). This approach provides a robust single-step route to peptide moieties connected to N-heterocyclic motifs that are found as core skeletons in many natural products and pharmaceutical compounds. JU-3CRs also provide much better diastereoselectivity than their four-component analogues. We survey here the redesign of many synthetic routes for the efficient preparation of a wide variety of three-, five-, six-, and seven-membered heterocyclic compounds connected to the peptide backbone. Additionally, in the Ugi reactions based on the cyclic imines, α-acidic isocyanides, or azides can be replaced with normal isocyanides or acids, respectively, leading to the synthesis of N-heterocycles attached to oxazoles or tetrazoles, which are of great pharmaceutical significance. This Review includes all research articles related to Ugi reactions based on the cyclic imines to the year 2020 and will be useful to chemists in designing novel synthetic routes for the synthesis of individual and combinatorial libraries of natural products and drug-like compounds.

Asymmetric Synthesis of C1-Chiral THIQs with Imines in Isoquinoline Rings

Tetrahydroisoquinoline (THIQ) scaffolds are important structural units that widely exist in a variety of natural alkaloids and synthetic analogues. Asymmetric synthesis of C1-chiral THIQ is of particular importance due to its significant pharmaceutical, agrochemical, and other biological activities, and the usually distinct bioactivities exhibited by the two enantiomers. In this review, we highlight the significant advances achieved in this field, present recent asymmetric synthesis with imines in isoquinoline rings ordered according to the sequence of various substrate types. New strategies could be inspired and more types of substrates need further development.

1 Introduction

2 Catalytic Asymmetric Reaction of Dihydroisoquinolines

2.1 Asymmetric Reactions of 3,4-Dihydroisoquinolines

2.2 Asymmetric Reactions of Dihydroisoquinolinium Salts

2.3 Asymmetric Reactions of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.1 NED [3+2] Cycloaddition of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.2 IED [3+2] Cycloaddition of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.3 [3+3] Cycloaddition of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.4 [4+3] Cycloaddition of C,N-Cyclic N′-Acyl Azomethine Imines

2.3.5 Asymmetric Addition Reactions to C,N-Cyclic N′-Acyl Azomethine Imines

2.4 Asymmetric Reactions of C,N-Cyclic Nitrones

3 Catalytic Asymmetric Mannich Reactions of Isoquinolines

4 Conclusions and Perspectives

Ag2O-catalysed nucleophilic isocyanation: selective formation of less-stable benzylic isonitriles

Both primary and secondary benzylic isonitriles were exclusively produced by the Ag₂O-catalysed reaction of benzylic phosphates and trimethylsilyl cyanide without formation of the thermodynamically favoured regioisomers, benzylic nitriles.

A rhodium-catalysed three-component reaction to access C1-substituted tetrahydroisoquinolines

A rhodium-catalyzed three-component reaction of diazo compounds, anilines and C,N-cyclic azomethine imines via trapping of transient ammonium ylides was developed. This reaction provided a simple and convenient approach for the synthesis of pharmaceutically intriguing tetrahydroisoquinoline derivatives in moderate to good yields (36-85%) with good diastereoselectivities (up to 95 : 5 dr) under mild reaction conditions.

Nickel-Mediated Asymmetric Allylic Alkylation between Nitroallylic Acetates and Acyl Imidazoles

A nickel-mediated asymmetric allylic alkylation reaction between imidazole-modified ketones and nitroallylic acetates is presented. This reaction is catalyzed by a simple chiral diamine-nickel catalyst under mild conditions and leads to a series of novel enantioenriched α-allylic adducts in moderate to good yields with excellent enantioselectivities. Furthermore, transformation of the allylic adducts could smoothly lead to chiral γ-nitro-esters containing three continuous stereocenters in good yields.