Catalytic Enantioselective α,β,γ-Trioxygenation

DyKAT by DiCat: Stereoconvergent Dienamine-Catalyzed Claisen Rearrangements

This Claisen rearrangement establishes the feasibility of DyKAT of γ-epimeric enals via dienamine formation to afford enantioenriched products. γ-Aryl and -alkyl enals, and exocyclic enals that introduce quaternary centers, are all amenable substrates. Products are readily converted into pyrrolidines or cyclopentenols. Notably, a reactive dienamine intermediate has been isolated from a catalytic reaction, fully characterized, and converted to product upon reexposure to reaction conditions. Product configuration arises from a directing C-H···π interaction in the transition state.

Combining Palladium and Chiral Organocatalysis for the Enantioselective Deconjugative Allylation of Enals via Dienamine Intermediates

A catalytic enantioselective deconjugative allylation of enals is reported. A variety of enals underwent this transformation in high yield and ee, and products can be readily transformed into γ-allyl enals via a Cope rearrangement without erosion of ee. This transformation was used to install the quaternary stereocenter in (S)-bakuchiol, enabling completion of a concise formal synthesis.

Trifunctionalization of alkenes and alkynes

In this review, the development of trifunctionalization methods for alkenes and alkynes, including arynes and allenes, over the last decade is disclosed.

Combinations of Aminocatalysts and Metal Catalysts: A Powerful Cooperative Approach in Selective Organic Synthesis

The cooperation and interplay between organic and metal catalyst systems is of utmost importance in nature and chemical synthesis. Here innovative and selective cooperative catalyst systems can be designed by combining two catalysts that complement rather than inhibit one another. This refined strategy can permit chemical transformations unmanageable by either of the catalysts alone. This review summarizes innovations and developments in selective organic synthesis that have used cooperative dual catalysis by combining simple aminocatalysts with metal catalysts. Considerable efforts have been devoted to this fruitful field. This emerging area employs the different activation modes of amine and metal catalysts as a platform to address challenging reactions. Here, aminocatalysis (e.g., enamine activation catalysis, iminium activation catalysis, single occupied molecular orbital (SOMO) activation catalysis, and photoredox activation catalysis) is employed to activate unreactive carbonyl substrates. The transition metal catalyst complements by activating a variety of substrates through a range of interactions (e.g., electrophilic π-allyl complex formation, Lewis acid activation, allenylidene complex formation, photoredox activation, C-H activation, etc.), and thereby novel concepts within catalysis are created. The inclusion of heterogeneous catalysis strategies allows for "green" chemistry development, catalyst recyclability, and the more eco-friendly synthesis of valuable compounds.