Table 3.
Substituted 2-Azadienes for Enantioselective Additions to Ketonesa
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|---|---|---|---|---|
|
| ||||
| entry | product, R | dr of 3b | yield (%)c | erd |
| 1 | 7a, n-Bu | >20:1 | 43 | 96.5:3.5 |
| 2e | 7b, (CH2)2Ph | >20:1 | 54 | 98.5:1.5 |
| 3 | 7c, (CH2)2(3-thiophenyl) | >20:1 | 52 | >99:1 |
| 4f | 7d, (CH2)2SMe | >20:1 | 52 | 98.5:1.5 |
| 5 | 7e, (CH2)3Ph | >20:1 | 45 | 98:2 |
| 6 | 7f, (CH2)3OBn | >20:1 | 47 | 98:2 |
| 7 | 7g, (CH2)3OPh | >20:1 | 59 | 99:1 |
| 8 | 7h, (CH2)3OTBS | >20:1 | 45 | 98.5:1.5 |
| 9 | 7i, (CH2)4OBz | >20:1 | 46 | 99:1 |
| 10 | 7j, (CH2)4C1 | >20:1 | 48 | 98.5:1.5 |
a
Reaction of (E)-azadiene 1 unless otherwise noted.
b
Determined by 400 MHz 1H NMR spectroscopy of the unpurified mixture prior to workup.
c
Isolated yield of purified 7.
d
Enantiomeric ratio determined by HPLC analysis of 7.
e
(E)- and (Z)-azadienes 1c deliver identical results.
f
From (Z)-1e.