TY - JOUR
T1 - Room-Temperature Benzylic Alkylation of Benzylic Carbonates
T2 - Improvement of Palladium Catalyst and Mechanistic Study
AU - Kuwano, Ryoichi
AU - Yokogi, Masashi
AU - Sakai, Ken
AU - Masaoka, Shigeyuki
AU - Miura, Takashi
AU - Won, Sungyong
N1 - Funding Information:
This work was partly supported by the JSPS KAKENHI Grants JP16H04149 and JP15KT0066. We thank the Cooperative Research Program of “Network Joint Research for Material Devices” for HRMS measurements.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/8/16
Y1 - 2019/8/16
N2 - The palladium catalyst for the nucleophilic substitution of benzyl carbonates was improved by using 1,1′-bis(diisopropylphosphino)ferrocene (DiPrPF) as the ligand. The [Pd(η3-C3H5)(cod)]BF4-DiPrPF catalyst allows the benzylic substitution with soft carbanions to proceed even at 30 °C, affording the desired products in high yields (up to 99% yield). Thermally unstable pyridylmethyl esters are employable as the electrophilic substrates for the benzylic alkylation with the improved catalyst. Furthermore, we investigated the mechanism of the catalytic benzylic alkylation by means of DiPrPF ligand. The palladium(0) complex bearing DiPrPF activates the benzylic C-O bond to form the (benzyl)palladium(II) intermediate at room temperature. The coordination mode of the benzyl ligand would be equilibrium between the η1- and η3-manner. The nucleophile would preferentially react with the η3-benzyl ligand to give the desired product.
AB - The palladium catalyst for the nucleophilic substitution of benzyl carbonates was improved by using 1,1′-bis(diisopropylphosphino)ferrocene (DiPrPF) as the ligand. The [Pd(η3-C3H5)(cod)]BF4-DiPrPF catalyst allows the benzylic substitution with soft carbanions to proceed even at 30 °C, affording the desired products in high yields (up to 99% yield). Thermally unstable pyridylmethyl esters are employable as the electrophilic substrates for the benzylic alkylation with the improved catalyst. Furthermore, we investigated the mechanism of the catalytic benzylic alkylation by means of DiPrPF ligand. The palladium(0) complex bearing DiPrPF activates the benzylic C-O bond to form the (benzyl)palladium(II) intermediate at room temperature. The coordination mode of the benzyl ligand would be equilibrium between the η1- and η3-manner. The nucleophile would preferentially react with the η3-benzyl ligand to give the desired product.
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U2 - 10.1021/acs.oprd.9b00210
DO - 10.1021/acs.oprd.9b00210
M3 - Article
AN - SCOPUS:85071440035
SN - 1083-6160
VL - 23
SP - 1568
EP - 1579
JO - Organic Process Research and Development
JF - Organic Process Research and Development
IS - 8
ER -