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Mechanistic Study of Nickel-Catalyzed Reductive Coupling of Ynoates and Aldehydes
- Rodrigo, Sanjeewa
K., Guan, Hairong
- Journal of organic chemistry 2017 v.82 no.10 pp. 5230-5235
- aldehydes, catalysts, catalytic activity, chemical oxygen demand, chemical reactions, chemical structure, dissociation, nickel, organic chemistry, regioselectivity, silane
- In this work, (1,5-hexadiene)Ni(SIPr) (SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene) is used in place of Ni(COD)₂/SIPr·HBF₄/KOᵗBu (COD = 1,5-cyclooctadiene) as a more robust catalyst for regioselective reductive coupling of ynoates and aldehydes with triethylsilane. The catalytic reaction of ethyl 3-(trimethylsilyl)propiolate and methyl 4-formylbenzoate shows first-order dependence on aldehyde and catalyst concentrations, inverse first-order dependence on [ynoate], and no dependence on [silane]. The kinetics data, coupled with deuterium-labeling experiments, support a mechanism involving dissociation of the ynoate from a catalytically dormant nickelacyclopentadiene intermediate prior to turnover-limiting formation of a catalytically active nickeladihydrofuran.