Page 159 - Advanced Organic Chemistry Part A - Structure and Mechanisms, 5th ed (2007) - Carey _ Sundberg

Of course, the high conversion required for high enantiomeric purity when the relative 139
reactivity difference is low has a serious drawback. The yield of the unreacted substrate
is low if the overall conversion is high. Relative reactivity differences of < 10 can SECTION 2.1
achieve high enantiomeric purity only at the expense of low yield. Configuration
Scheme 2.5 gives some specific examples of kinetic resolution procedures. Entries
1to 3 in Scheme 2.5 are acylation reactions in which esters are formed. Either the

Scheme 2.5. Examples of Kinetic Resolution
O
1 a N CHCH 3 + (PhOCHC) 2 O N CHCH 3 + PhOCHCO 2 H
OH CH O CCHOPh CH 3
2
S-enantiomer racemic 3 S-enantiomer
CH
92% R, S-ester 3 84% e.e.
8% S, S ester
2 b OCH 3 + OCH
NH 3 + 3
+ (CH ) CH H
3 2
OH CO 2 – O C CH(CH 3 ) 2
L-valine 2
racemic, trans NH 2
27% yield, 96% d.e.
CH
3
O CCCCl 3
2
OH CH 3 O CH CH 3 +
3 c 3
CH 3 + Cl CCOC N+ ZnCl 2
3
S-enantiomer OH
91% e.e.
CH 3
CH 3 O C(CH )
racemic 3 3 CH 3
R-enantiomer
38% e.e. at 30% conversion
4 d
Ti(Oi Pr) 4
N CH CHPh N CH CHPh
2
2
t BuOOH
OH OH
(+)-diisopropyl
tartrate
recovered 37% yield, 95% e.e.
OH OH
5 e S-BINAP
Ru(OAc) , H R-enantiomer
CH 3 2 2 CH
3
recovered yield 48%, 96% e.e.
Ti(Oi Pr) 4 O
6 f
R-BINOL
CH SCH CH SCH
3 3 3 3
t BuOOH
31% yield, 97% e.e.
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Tetrahedron: Asymmetry, 7, 2247 (1996).
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