222
M. Rueping, E. Sugiono
Fig. 7. Brønsted acid catalyzed transfer hydrogenation of benzoxazines and
benzthiazines
Table 4 Evaluation of the catalyst loading for the enantioselective transfer
hydrogenation
Entry
Loading of 5b [%]
Yield [%] a
ee [%] b
1
1 0
9 1
9 6
2
5
95
96
3
2
93
96
4
1
94
96
5
0.1
95
96
6
0 . 0 1
9 0
9 3
a Isolated yields of 13a after chromatography
b Enantioselectivities were determined by HPLC analysis