Page 714 - Advanced Organic Chemistry Part A - Structure and Mechanisms, 5th ed (2007) - Carey _ Sundberg

696

CHAPTER 7 π-π Interaction
Addition, Condensation
and Substitution
Reactions of Carbonyl
Compounds re

Nuc

Fig. 7.15. Facial selectivity of
3-indolylmethyloxaborazolidinone
catalyst. Reproduced from Tetra-
hedron Asymmetry, 9, 357 (1998),
by permission of Elsevier. (See also
color insert.)

The B-3,5-di(trifluoromethyl)phenyl derivative was found to be a very effective
catalyst. 123

O
N
H N O
B
Ts
CH OTMS OH O
CH O 3 R
+
Ph Ph
CH 3
R = 3,5-di(trifluoromethyl)phenyl > 99:1 syn; > 99% e.e.

Another effective group of catalysts is made up of the copper bis-oxazolines. 124

O O

O But N N tBu
OTMS Cu OH O
+ CH 3
CH CCO CH CH 3 CH 2 CF SO O OSO CF 3
3
2
2
2
2
3
R CH 3 O C R
2
R = CH , C H
6 5
3
123 K. Ishihara, S. Kondo, and H. Yamamoto, J. Org. Chem., 65, 9125 (2000).
124
D. A. Evans, J. A. Murry, and M. C. Kozlowski, J. Am. Chem. Soc., 118, 5814 (1996).