Page 31 - Demo-1

DKR Utilizing Organocatalysts
DKR of azlactones using urea-based bifunctional organocatalysts
H-bond donor H-bond donor OO
R N N * chiralspacer R N N HH HH
* chiralspacer
NR2 Bronsted base
H
NR2 Bronsted base O
O HOOH
R2N R3 O R1
R2 N
R1
N
R
O
O
catalyst (5 mol%)
allyl alcohol (1.5 equiv) Ph
PhCH3, RT, 48 h
O R
N H
H
O allyl O
Ph
R = PhCH2, Me, iPr, iBu, tBu, Ph
43-96% conversion, 72-87% ee
Berkessel, A.; Cleemann, F.; Mukherjee, S.; Muller, T. N.; Lex, J. Angew. Chem. Int. Ed. Engl. 2005, 44, 807
CF3
O
F3C NHNH
NMe2
urea-based catalyst
DKR Utilizing Organocatalysts
Asymmetric Synthesis of α-Hydroxy Carboxylic Acids
R
O
O
(DHQD)2AQN (10 mol%) EtOH (1.5 equiv), Et2O
RHO
OO
O
O
OH
61-85% yield 60-96% ee
O
OH
R
OEt
O
O R = aryl
O R
O
O
R'OH, NR3* fast
R
OR'
OR'
HNR3* +
O
RHO O
O O R'OH, NR3* R slow
O Racemization rate with R=alkyl was too slow to allow for efficient DKR
OH
Tang, L.; Deng, L. J. Am. Chem. Soc. 2002, 124, 2870