Table 1 Optimization of reaction conditionsa.
From: Copper(I)-catalyzed asymmetric 1,6-conjugate allylation
| ||||
|---|---|---|---|---|
Entry | Ligand | T | Yieldb | ee (%)c |
1 | (R)-BINAP | rt | 25 | 9 |
2 | (R)-DTBM-SEGPHOS | rt | 44 | 20 |
3 | (R,R)-Ph-BPE | rt | 58 | 38 |
4 | (R,R)-QUINOXP* | rt | trace | – |
5 | (R,Rp)-TANIAPHOS | rt | 20 | 2 |
6 | (R)-(S)-JOSIPHOS | rt | 46 | 23 |
7 | NHC-L1 | rt | 14 | 0 |
8 | NHC-L2 | rt | 12 | 8 |
9 | NHC-L3 | rt | 10 | 64 |
10 | NHC-L4 | rt | 31 | 90 |
11 | NHC-L5 | rt | 54 | 82 |
12d | NHC-L4 | rt | 50 | 90 |
13d,e | NHC-L4 | rt | 85 | 89 |
14d,e | NHC-L4 | −20 | 53 | 95 |
15d,f | NHC-L4 | −20 | 84 | 94 |
- a1a: 0.1 mmol, 2: 0.2 mmol.
- bDetermined by 1H NMR analysis of reaction crude mixture using mesitylene as an internal standard.
- cDetermined by chiral-stationary-phase HPLC analysis.
- d10 mol % Cu(CH3CN)4PF6 and 12 mol % NHC-L4 were used.
- e2 equiv LiOtBu were employed.
- f3 equiv 2 and 3 equiv LiOtBu were employed.
