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A Bifunctional Copper Catalyst Enables Ester Reduction with H 2 : Expanding the Reactivity Space of Nucleophilic Copper Hydrides

2021; American Chemical Society; Volume: 143; Issue: 40 Linguagem: Inglês

10.1021/jacs.1c09626

1943-2984

Birte Zimmermann, Trung Tran Ngoc, Dimitrios‐Ioannis Tzaras, Trinadh Kaicharla, Johannes F. Teichert,

Catalytic Cross-Coupling Reactions

Employing a bifunctional catalyst based on a copper(I)/NHC complex and a guanidine organocatalyst, catalytic ester reductions to alcohols with H2 as terminal reducing agent are facilitated. The approach taken here enables the simultaneous activation of esters through hydrogen bonding and formation of nucleophilic copper(I) hydrides from H2, resulting in a catalytic hydride transfer to esters. The reduction step is further facilitated by a proton shuttle mediated by the guanidinium subunit. This bifunctional approach to ester reductions for the first time shifts the reactivity of generally considered "soft" copper(I) hydrides to previously unreactive "hard" ester electrophiles and paves the way for a replacement of stoichiometric reducing agents by a catalyst and H2.