α-Nitro-α,β-Unsaturated Ketones: An Electrophilic Acyl Transfer Reagent in Catalytic Asymmetric Friedel–Crafts and Michael Reactions

Asymmetric Friedel-Crafts reaction of unsaturated carbonyl-tethered heteroarenes via vinylogous activation of Pd0-π-Lewis base catalysis

The alkyne group can undergo facile transformations under palladium catalysis, such as hydropalladation, Wacker reaction, etc. Here we demonstrate that a chiral Pd0 complex can chemoselectively dihapto-coordinate to the alkyne moiety of 2-indolyl propiolates, and raise the Highest Occupied Molecular Orbital (HOMO)-energy ofthe deactivated heteroarenes via π-Lewis base catalysis. As a result, asymmetric C3-selective Friedel-Crafts addition to activated alkenes occurs, finally affording [3 + 2] or [3 + 4] annulation products with high enantioselectivity and exclusive E-selectivity. Moreover, this π-Lewis base vinylogous HOMO-activation strategy can be extended to remote Friedel-Crafts reaction of diverse five-membered heteroarenes tethered to a 2-enone or 2-acrylate motif with imines or 1-azadienes, and excellent enantiocontrol is generally achieved for the multifunctional adducts, which can be effectively converted to diverse frameworks with higher molecular complexity. In addition, NMR and density functional theory calculation studies are conducted to elucidate the catalytic mechanism.

Organocatalytic Asymmetric Domino [3+2]-Cycloaddition-Acyl Transfer Reaction between Azomethine Ylides and α-Nitro-α,β-Unsaturated Ketones

Herein we have developed an organocatalytic asymmetric domino [3+2]-cycloaddition-acyl transfer reaction between in situ generated azomethine ylides and α-nitro-α,β-unsaturated ketones. The desired penta-substituted pyrrolidine products were obtained in high yields and in moderate to good enantio- and diastereoselectivities. Also, an isomerization reaction in silica gel was performed for the formation of another diastereomer in high yields with retention of enantioselectivities.

Zinc-Catalyzed Asymmetric Cascade Michael/Acyl Transfer Reaction between α-Hydroxy Aryl Ketones and Enynones

We described herein a neoteric enantioselective cascade Michael/acyl transfer reaction of enynones and α-hydroxy aryl ketones catalyzed by dinuclear zinc cooperative catalysis. A series of structurally diverse chiral 1,5-dicarbonyl compounds were synthesized in good yields with excellent stereoselectivities. This strategy features broad substrate scope, high atom economy, as well as enynones as efficient electrophilic acyl transfer reagents in asymmetric cascade reactions for the first time.

Unravelling the Development of Non-Covalent Organocatalysis in India

This review is devoted to underpinning the contributions of Indian researchers towards asymmetric organocatalysis. More specifically, a comprehensive compilation of reactions mediated by a wide range of non-covalent catalysis is illustrated. A detailed overview of vividly catalogued asymmetric organic transformations promoted by hydrogen bonding and Brønsted acid catalysis, alongside an assortment of catalysts is provided. Although asymmetric organocatalysis has etched itself in history, we aim to showcase the scientific metamorphosis of Indian research from baby steps to large strides within this field.

1 Introduction

2 Non-Covalent Catalysis and Its Various Activation Modes

3 Hydrogen-Bonding Catalysis

3.1 Urea- and Thiourea-Derived Organocatalysts

3.1.1 Thiourea-Derived Organocatalysts

3.1.2 Urea-Derived Organocatalysts

3.2 Squaramide-Derived Organocatalysts

3.2.1 Michael Reactions

3.2.2 C-Alkylation Reactions

3.2.3 Mannich Reactions

3.2.4 [3+2] Cycloaddition Reactions

3.3 Cinchona-Alkaloid-Derived Organocatalysts

3.3.1 Michael Reactions

3.3.2 Aldol Reactions

3.3.3 Friedel–Crafts Reactions

3.3.4 Vinylogous Alkylation of 4-Methylcoumarins

3.3.5 C-Sulfenylation Reactions

3.3.6 Peroxyhemiacetalisation of Isochromans

3.3.7 Diels–Alder Reactions

3.3.8 Cycloaddition Reactions

3.3.9 Morita–Baylis–Hilman Reactions

4 Brønsted Acid Derived Organocatalysts

4.1 Chiral Phosphoric Acid Catalysis

4.1.1 Diels–Alder Reactions

4.1.2 Addition of Ketimines

4.1.3 Annulation of Acyclic Enecarbamates

5 Conclusion

Recent advances in the applications of pyrazolone derivatives in enantioselective synthesis

Pyrazolones and pyrazoles, featuring nitrogen-nitrogen bonds, are two of the most important classes of heterocycles, owing to their widespread occurrence in medicinal chemistry and functional materials. The last decade has witnessed a rapid increase in the construction of chiral pyrazolone and pyrazole derivatives, with the application of pyrazolone derivatives as powerful synthons. Since our last review in 2018, a large number of new achievements has emerged in this area, requiring a timely update. Thus, this review summarizes these elegant achievements based on the multiple reactive sites of different pyrazolone synthons. In addition, important mechanisms and interesting biological investigations relating to the corresponding products are also discussed.