Chemistry Reference
In-Depth Information
- ketoesters
45
to acrolein (
84A
),
a catalyst loading as low as 0.1 mol % suffi ces to give clean and highly stereoselective
reactions. These data indicate that the high catalyst loading observed with less active
substrates is not due to catalyst decomposition or product inhibition, but instead it is
limited by the slow catalyst turnover rate. Another commonly observed trend is that the
enantioselectivity of the catalyst is quite insensitive to the steric properties of the sub-
strates. Instead, the enantioselectivity of the catalyst was often found to depend on the
activity of both the nucleophile and electrophile. For example, a broader range of
nucleophiles can be successfully employed in conjugate additions with a class of rela-
tively active Michael acceptors such as nitroalkenes
60
versus those with less active
Michael acceptors such as
dialkyl azadicarboxylates or the conjugate addition of
β
α
,
β
- unsaturated ketones
41
[47,48,49b]. In parallel, a more
active Michael donor, such as
- ketoesters
45
, could be successfully applied in reactions
with a broader range of Michael acceptors. Thus, the development of new classes of
more active acid-base bifunctional catalysts is of central importance from the viewpoint
of expanding the reaction scope as well as improving the practicality of asymmetric
acid - base bifunctional catalysis.
β
ACKNOWLEDGMENTS
We are grateful for the fi nancial support from the National Institute of Health (National
Institute of General Medical Sciences, R01-GM61591) and Daiso. We sincerely thank
our colleagues, Mr. Xiaojie Lu and Dr. Yan Liu, for their help during the preparation
of the chapter.
REFERENCES
1. (a)
Acc. Chem. Res.
2004
,
37
, 487, Special Issue: Asymmetric Organocatalysis. (b)
Chem. Rev.
2007
,
107
, 5413, Special Issue: Organocatalysis.
2. Silverman , R. B.
The Organic Chemistry of Enzyme-Catalyzed Reactions
. San Diego, CA : Academic
Press , 2000 .
3. (a) Yamamoto , H.
Lewis Acids in Organic Synthesis
. New York : Wiley ,
2000
. (b) Jacobsen , E. N. ;
Pfaltz , A. ; Yamamoto , H.
Comprehensive Asymmetric Catalysis
. Berlin : Springer , 1999 ; Vols. 1 - 3.
(c) Satelli , M. ; Pons , J. - M.
Lewis Acid and Selectivity in Organic Synthesis
. Boca Raton, FL: CRC
Press , 1996 .
4. For reviews of asymmetric catalysis by hydrogen - bond donors, see: (a) Taylor , M. S. ; Jacobsen , E. N.
Angew. Chem. Int. Ed. Engl.
2006
,
45
, 1520 . (b) Doyle , A. G. ; Jacobsen , E. N.
Chem. Rev.
2007
,
107
, 5713 .
5. Selected examples of hydrogen bond - donor catalyzed racemic reactions: (a) Kelly , T. R. ; Meghani ,
P. ; Ekkundi , V. S.
Tetrahedron Lett.
1990
,
31
, 3381 . (b) Curran , D. P. ; Kuo , L. H.
J. Org. Chem.
1994
,
59
, 3259 . (c) Curran , D. P. ; Kuo , L. H.
Tetrahedron Lett.
1995
,
36
, 6647 .
6. (a) Sigman , J. S. ; Jacobsen , E. N.
J. Am. Chem. Soc.
1998
,
120
, 4901 . (b) Sigman , J. S. ; Vachal , P. ;
Jacobsen , E. N.
Angew. Chem. Int. Ed. Engl.
2000
,
39
, 1279 .
7. Vachal , P. ; Jacobsen , E. N.
Org. Lett.
2000
,
2
, 867 .
8. Vachal , P. ; Jacobsen , E. N.
J. Am. Chem. Soc.
2002
,
124
, 10012 .
9. (a) Joly , G. D. ; Jacobsen , E. N.
J. Am. Chem. Soc.
2004
,
126
, 4102 . (b) Wenzel , A. G. ; Jacobsen ,
E . N .
J. Am. Chem. Soc.
2002
,
124
, 12964 .
10. Corey , E. J. ; Grogan , M. J.
Org. Lett.
1999
,
1
, 157 .
11. (a) Huang , Y. ; Rawal , V. H.
J. Am. Chem. Soc.
2002
,
124
, 9662 . (b
)
Huang , Y. ; Unni , A. K. ; Rawal ,
V . H .
Nature
2003
,
424
, 146 .
(
c) Thadani , A. N. ; Stankovic , A. R. ; Rawal , V. H.
Proc. Natl. Acad. Sci.
