Kinetic resolution of racemic α-tert-alkyl-α-hydroxy esters by enantiomer-selective carbamoylation.
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.
Division of Chemical Process Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan.
Nobuhito
N
Kurono
Kentaro
K
Ohtsuga
Masanori
M
Wakabayashi
Tadahiro
T
Kondo
Hirohito
H
Ooka
Takeshi
T
Ohkuma
D002219:Carbamates / Q000737:chemistry*; D002384:Catalysis; D004952:Esters / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D010080:Oxazoles / Q000737:chemistry; D013237:Stereoisomerism
D002219:Carbamates; D004952:Esters; D010080:Oxazoles