Pyrazoleamides in Catalytic Asymmetric Reactions: Recent Advances

Pyrazoleamides are a class of compounds which have received significant attention in the last years in asymmetric catalysis as more reactive and practical surrogates of esters or amides. These readily available reagents have served in a variety of diastereo- and enantioselective metal- and organocatalytic transformations, spanning from simple carbon-carbon or carbon-heteroatom bond formation to cascade and rearrangement reactions, to produce valuable classes of heterocyclic compounds. More recently, pyrazoleamides have proved to be pertinent reagents in asymmetric catalysis merged with photoredox catalysis, and in more challenging stereoselective bond-forming reactions, occurring directly from a visible-light activated substrate/catalyst complex without any charge separation. Both strategies enable new activation concepts useful for the production of difficult-to-access intermediates and pharmaceuticals. In this review, an overview of the progress achieved in asymmetric catalytic reactions of pyrazoleamides from 2015 up to middle 2020, is illustrated.1. Introduction2. Pyrazoleamides as Electrophiles in Organocatalysis3. Pyrazoleamides as Nucleophiles in Organocatalysis4. Pyrazoleamides as Electrophiles in Metal Catalysis5. Pyrazoleamides as Nucleophiles in Metal Catalysis6. Rearrangements of alpha-Diazo Pyrazoleamides7. Combined Metal- and Organocatalysis8. Pyrazoleamides in Visible-Light-Activated Photochemical Reactions8.1. Merging Visible Light Photoredox Activation with Asymmetric Catalysis8.2. Stereocontrolled Direct Photoreactions from Electronically Excited State8.3. Merging HAT Photocatalysis with Chiral Lewis Acid Catalysis9. Summary and Outlook