Catalytic Asymmetric Reactions by Metal and Chiral Phosphoric Acid Sequential Catalysis

Abstract

Catalytic asymmetric reactions promoted by metal catalysts and chiral phosphoric acids have become useful processes for the preparation of structurally diverse and complex organic compounds. This JOCSynopsis provides an overview of the most recent developments made in studies of these reactions. The paper focuses mainly on sequential catalysis and relay catalysis, which are accomplished by employing a combination of metal complexes and chiral phosphoric acids.

Catalytic Asymmetric Radical Diamination of Alkenes

“…To our delight, the desired 1,2-diamination product 3A was obtained in 85% yield, albeit with low enantioselectivity (13% ee) ( Table 1, entry 1). Under these reaction conditions, a variety of BINOL-and SPINOL-based CPAs [63][64][65][66][67][68][69][70][71] were initially evaluated (entries 1-6) and good results (52% ee, entry 4) were obtained with SPINOL-based (S)-A4 with 4-Ph-phenyl groups at the 3,3 0 -positions of the backbone. We next screened a series of Cu(I) catalysts and organic solvents (entries 7-13) and found that the use of Cu(CH 3 CN) 4 BF 4 as catalyst in 1,4-dioxane was the best (57% yield and 86% ee; entry 10).…”

Recent Developments in Enantioselective Multicatalyzed Tandem Reactions

“…When the two catalysts are incompatible, the tandem reaction can nevertheless be performed by adding them successively to the reaction media (sequential catalysis). In spite of these difficulties there are, however, many beautiful examples of asymmetric tandem reactions based on the use of combinations of organocatalysts with various types of metal complexes, acting through cooperative, relay as well as sequential catalysis …”

Tandem Chiral Cu(II) Phosphate‐Catalyzed Deoxygenation of Nitrones/Enantioselective Povarov Reaction with Enecarbamates

“…In continuation of our research program in catalytic asymmetric cycloadditions with enecarbamates, we became interested in exploring their reactivity in connection with nitrones. We speculated that chiral phosphoric acid catalysts or their corresponding metal salts[7b], could promote enantioselective (3+2) cycloaddition to deliver valuable isoxazolidines 4 . Indeed, as the nitrones and enecarbamates can be activated by these catalysts via hydrogen bonding[3b] and/or metal chelation, reactivity and high stereoselectivity might be achieved (Scheme ).…”