Kinetic resolution of racemic α-tert-alkyl-α-hydroxy esters by enantiomer-selective carbamoylation
Nobuhito Kurono1, Kentaro Ohtsuga, Masanori Wakabayashi
1Division of Chemical Process Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan.
Abstract:
Kinetic resolution of sterically hindered racemic α-tert-alkyl-α-hydroxy esters is performed by enantiomer-selective carbamoylation with the t-Bu-Box-Cu(II) catalyst (Box = bis(oxazoline)). The reaction with 0.5 equiv of n-C(3)H(7)NCO is carried out with a substrate-to-catalyst molar ratio of 500-5000 at -20 to 25 °C. The high enantiomer-discrimination ability of the catalyst achieves an excellent stereoselectivity factor (s = k(fast)/k(slow)) of 261 in the best case. A catalytic cycle for this reaction is proposed.
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