Kinetic Resolutions - The Stoltz Group
Kinetic Resolutions - The Stoltz Group
Kinetic Resolutions - The Stoltz Group
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(±)-<br />
R 1<br />
OH<br />
R 2<br />
An Improved Phosphine Catalyst - Vedejs<br />
5 mol% Catalyst 6<br />
(RCO) 2 O<br />
-40 o C<br />
PhCH 3 / heptane<br />
R 1 = Ar, R 2 = Alkyl, R = Ph, i-Pr<br />
1-24 hours, s = 6.9 - 390<br />
Catalyst %ee important<br />
R 1<br />
OH<br />
R 2<br />
R 1<br />
OCOR<br />
r.t. to -40 o C decreases rate only 8-fold, but enantioselectivity is much higher<br />
Ph anhydride faster but less selective<br />
Catalyst Ar - Ph, 3,5-tBu 2Ph, 2,4,6-Me 3Ph : generally increasing selectivity<br />
heptane generally faster reactions - believed to be because of tighter ion pairing of carboxylate and<br />
carbonylated catalyst<br />
Allylic alcohols also worked (s = 4-82), but only when there was significant steric direction<br />
<strong>Resolutions</strong> based purely on sterics of R 1 and R 2 gave no selectivity<br />
+<br />
R 2<br />
H<br />
P<br />
H<br />
Catalyst 6<br />
Vedejs, et. al., Synlett, 2001, 10, 1499<br />
J. Am. Chem. Soc., 2003, 125, 4166<br />
Ar<br />
8
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