Hydrocarboxylation of alkynes with formic acid over multifunctional ligand modified Pd-catalyst with co-catalytic effect

Atmospheric hydroxycarbonylation of alkynes with HCOOH over Pd-catalyst modified by the multiple-functional ligand of L2. [Display omitted] •Atmospheric hydrocarbonylation of alkynes with formic acid free of CO and water.•The multifunctional ligand modified Pd-catalyst featured with co-catalytic eff...

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Bibliographic Details
Published in:Journal of catalysis 2022-01, Vol.405, p.322-332
Main Authors: Liu, Lei, Yao, Yin-Qing, Chen, Xiao-Chao, Guo, Lin, Lu, Yong, Zhao, Xiao-Li, Liu, Ye
Format: Article
Language:English
Subjects:
CO surrogate
Co-catalytic effect
Formic acid
Hydrocarboxylation
Hydrogen source
Multifunctional ligand
α,β-Unsaturated carboxylic acids
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Summary:Atmospheric hydroxycarbonylation of alkynes with HCOOH over Pd-catalyst modified by the multiple-functional ligand of L2. [Display omitted] •Atmospheric hydrocarbonylation of alkynes with formic acid free of CO and water.•The multifunctional ligand modified Pd-catalyst featured with co-catalytic effect.•Formic acid not only serving as CO-surrogate but also as proton/formate donor.•Synergetic activation of formic acid by the multifunctional ligand. Hydrocarboxylation of terminal alkynes with formic acid (FA) was accomplished over a multifunctional ligand (L2) modified Pd-catalyst, advantageous with 100% atom-economy, free use of CO and H2O, mild reaction conditions, and high yields (56–89%) of α,β-unsaturated carboxylic acids with 100% regioselectivity to the branched ones. The multifunctional ligand of L2 as a zwitterion salt containing the phosphino-fragment (-PPh2), Lewis acidic phosphonium cation and sulfonate group (-SO3−), was constructed on the skeleton of 1.1′-binaphthyl-2.2′-diphenyl phosphine (BINAP) upon selective quaternization by 1,3-propanesultone. It was found that L2 conferred to the Pd-catalyst the co-catalytic effect, wherein the phosphino-coordinated Pd-complex was responsible for activation of all the substrates (including CO, FA and alkyne), and the incorporated phosphonium cation was responsible for synergetic activation of FA. The 1H NMR spectroscopic analysis supported that FA was truly activated by the incorporated Lewis acidic phosphonium cation in L2 via “acid-base pair” interaction. The in situ FT-IR spectra demonstrated that, the presence of Ac2O and NaOAc additives in the catalytic amount could dramatically promote the in situ release of CO from FA, which was required to initiate the hydrocarboxylation.
ISSN:0021-9517
1090-2694
DOI:10.1016/j.jcat.2021.12.011