Abstract
A novel class of cyclic phosphine derived bifunctional catalysts (Le-Phos) is reported, which can be readily prepared from inexpensive and commercially available starting materials and exhibit good performances in enantioselective γ-addition reactions of N-centered nucleophiles and allenoates under mild conditions. The salient features of this reaction include high product yields, good enantioselectivity, mild reaction conditions, and broad substrate scope and gram-scale scalability.
Highlights
Over the past few years, asymmetric phosphine-catalyzed reactions have emerged as powerful and versatile tools for the construction of C–C and C–X bonds,[1] which relies very much on the evolution of various new chiral phosphine catalysts.[2]
There are mainly two types of chiral phosphine catalysts developed: highly nucleophilic monofunctional phosphine catalysts such as cyclic phosphines P1–P5 (Fig. 1, Type 1) and diphenylphosphine-derived bifunctional catalysts bearing a hydrogen donor such as P6–P9 (Fig. 1, Type 2). Both displayed good catalytic activities and were effective in enantiomeric control in asymmetric phosphine catalysis.1a,g,3 Recently, we developed several novel diphenylphosphine-derived bifunctional phosphines from commercially available chiral sul namide.[4]
Fu, Jacobsen, Lu and our groups have successfully expanded the scope of nucleophiles such as alcohols, thiols, carbon, amides and ketimines by the employment of different types of phosphine catalysts.[10]
Summary
Over the past few years, asymmetric phosphine-catalyzed reactions have emerged as powerful and versatile tools for the construction of C–C and C–X bonds,[1] which relies very much on the evolution of various new chiral phosphine catalysts.[2] There are mainly two types of chiral phosphine catalysts developed: highly nucleophilic monofunctional phosphine catalysts such as cyclic phosphines P1–P5 (Fig. 1, Type 1) and diphenylphosphine-derived bifunctional catalysts bearing a hydrogen donor such as P6–P9 (Fig. 1, Type 2) Both displayed good catalytic activities and were effective in enantiomeric control in asymmetric phosphine catalysis.1a,g,3 Recently, we developed several novel diphenylphosphine-derived bifunctional phosphines from commercially available chiral sul namide.[4] To further advance a new catalyst design, we aimed to combine the advantages of the aforementioned two types of phosphine catalysts, developing a novel bifunctional cyclic phosphine catalyst. We report the design and synthesis of Le-Phos, and its application in highly enantioselective phosphine catalyzed g-addition of N-centered nucleophiles to allenoates
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