Synergistic–cooperative combination of enamine catalysis with transition metal catalysis

Abstract

Synergistic-cooperative combination of enamine catalysis with transition metal catalysis is an emerging and exciting field aiming to achieve organic transformations that cannot be accomplished by individual catalysis. The biggest obstacle in this field lies in the catalyst incompatibility arising from Lewis acid-Lewis base interactions. Several strategies including soft/hard combination of a Lewis acid and a Lewis base, the utilization of a chelating ligand, and mixing an ammonium salt with a Lewis acid have been developed to solve the incompatibility problem. A number of new reactions and new reaction modes have been discovered using these strategies. In this review article, we aim to highlight these new discoveries found in the literature.

Practical Direct α‐Arylation of Cyclopentanones by Palladium/Enamine Cooperative Catalysis

“…Merging transition‐metal and enamine catalysis has enabled a number of powerful C−C bond‐forming transformations at the α‐position of carbonyl compounds . The mode of activation generally includes 1) nucleophilic attack of enamines on metal‐activated allyl, benzylic, propargyl, and alkynyl electrophiles; 2) 1,2‐ or 1,4‐addition to polar π bonds activated by Lewis‐acidic metals (Scheme b) . In addition, we recently reported a directed C−H insertion/metalation approach for ketone α‐alkylation– and alkenylation with olefins and alkynes.…”

From QCA (Quantum Cellular Automata) to Organocatalytic Reactions with Stabilized Carbenium Ions

“…A soon as the “golden rush in organocatalysis”89 was at its end, researchers were also trying to investigate the possibility of using metals in conjunction with organocatalysis 90. Which metals can be used in the presence of enamines?…”

“…A soon as the "golden rush in organocatalysis" [89] was at its end, researchers were also trying to investigate the possibility of using metals in conjunction with organocatalysis. [90] Which metals can be used in the presence of enamines? Water is present and it is necessary to recycle the amine used in catalytic amounts, and primary or secondary amines are normally used in 20 mol% as catalysts.…”

Enantioselective Syntheses of Heteroyohimbine Natural Products: A Unified Approach through Cooperative Catalysis

“…[13] Thel arge majority of publications utilizing enamine-catalyzed Michael additions have involved the use of electron-deficient Michael acceptors such as alkylidene malonates,n itro-olefins,a nd vinyl ketones. [14] Form ore challenging transformations,a dditives such as Brønsted acids, [15] H-bond donors, [16] and Lewis acids, [17] which generally facilitate conversion by activation of the electrophile, [18] are employed. Given all of this innovation, it is surprising that asymmetric intramolecular Michael additions [19] into simple unsaturated esters still remain underexplored, with reported examples typically involving stoichiometric amine and extended reaction times (3-4 weeks).…”