Download Lecture 1: Key Concepts in Stereoselective Synthesis

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Transcript
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Update to 2012
Bode Research Group
http://www.bode.ethz.ch/
Harada ACIE 2008, 47, 1088; CEJ 2008, 14, 10560; Bull. Chem. Soc. Jpn. 2010, 83, 19
-Da reported a similar indirect way of doing catalytic enantioselective Grignard addition.
-Catalytic asymmetric addition was achieved by deactivating Grignard reagents through chelation with bis[2(N,N-dimethylamino)ethyl]ether (BDMAEE).
-In this carbonyl addition reaction, MgBr2 and MgBr(OiPr) are formed. These Lewis acids promote the
background reaction to form the racemic product and thus lower the enantioselectivity of the process.
Addition and chelation of DBMAEE to the in situ generated MgBr2 and MgBr(OiPr) suppress their activity and
so the asymmetric catalytic additions can be highly enantioselective.
-The catalytically active specie is also a titanate.
-Reaction can be run at room temperature.
Da OL 2009, 11, 5578
2.3
Catalytic enantioselective alkyne addition
2.3.1 Boron alkynilide addition to aldehydes
-Corey’s boryl acetylides gives good yields and enantioselectivities.
Corey JACS 1994, 116, 3151
2.3.2
Alkylzinc-mediated enantioselective alkynylation of aldehyde
O
H
R1
R1
R2
Me2Zn (3 eq),
(S, S) 1 (10 mol %),
Toluene, 4 °C
OH
R1
R2
(68-99% ee)
= NO2, H, C4H4(2-binaphth), furyl, OCH3
R2 = Ph, TMS, -CH2OCH3, -CO2Et
O
H
CO2Me
Ph
Ph
N
Ph
g-hydroxy-a,b-acetylenic esters are
extremely versatile synthetic intermediates
5
HO
Ph
Ph
OH
N
Me
(S, S)-1
OH
Me2Zn (3 eq),
(S, S) 1 (10 mol %),
Toluene, 4 °C
Ph
OH
CO2Me
92% (95% ee)