基于靛红亚胺与甲亚胺叶立德的催化不对称环化反应来构建手性螺环骨架(3)
6 5fa 7-F/Bn/MeO (1f) 71 >95:5 93:7
7 5ga 7-Br/Bn/MeO (1g) 64 >95:5 89:11
8 5ha H/p-MeC6H4CH2/MeO (1h) 68 >95:5 94:6
9 5ia H/p-BrC6H4CH2/MeO (1i) 69 >95:5 97:3
10 5ja H/m-ClC6H4CH2/MeO (1j) 73 >95:5 96:4
11 5ka H/o-ClC6H4CH2/MeO (1k) 62 >95:5 95:5
12 5la H/Ph/MeO (1l) 71 >95:5 96:4
13 5ma H/Bn/PhO (1m) 67 >95:5 91:9
14 5na H/Bn/Me (1n) 71 >95:5 92:8
15 5oa H/Bn/F (1o) 76 >95:5 87:13
aUnless otherwise indicated, the reaction was carried out at 0.1 mmol scale in toluene (1 mL) with MgSO4 (100 mg) for 48 h, and the mole ratio of 1:2a:3 was 1:1.2:1.1. bIsolated yield. cThe dr value was determined by 1H NMR. dThe er value was determined by HPLC.
接下来，在最优条件下，我们对芳香醛2进行了底物拓展（Table 2）。显然，这一反应适合缺电子的芳香醛（entries 1-7），这些缺电子的芳醛参与反应后，可得到相应的环化产物5，且具有可观的收率(52% to 72%)，和较高的非对映选择性和对映选择性(>95:5 dr, 88:12 to 95:5 er)。相反，电中性的苯甲醛2h在反应中却表现出了较低的反应活性和对映选择性（entry 8）。此外，富电子的芳香醛2i-2j未能产生相应的产物5ai和5aj（entries 10-11）。这些结果都表明，醛的电子效应对于该1,3-偶极环加成反应，不管是反应活性还是反应对映选择性，都有着显著的影响。
Table 2 Substrate scope of aromatic aldehydes 2a
表2 芳香醛2的拓展a
entry 5 R (2) yield (%)b drc erd
1 5aa 4-NO2 (2a) 72 >95:5 95:5
2 5ab 4-CN (2b) 62 >95:5 89:11
3 5ac 4-CO2Me (2c) 62 >95:5 92:8
4 5ad 3-CN (2d) 52 >95:5 88:12
5 5ae 3-CF3 (2e) 60 >95:5 93:7
6 5af 3-F,4-Cl (2f) 65 >95:5 90:10
7 5ag 3-Cl,4-F (2g) 71 >95:5 88:12
9 5ah H (2h) 43 >95:5 72:28
10 5ai 3-Me (2i) trace - -
11 5aj 4-Me (2j) trace - -
a Unless otherwise indicated, the reaction was carried out at 0.1 mmol scale in toluene (1 mL) with MgSO4 (100 mg) for 48 h, and the mole ratio of 1a:2:3 was 1:1.2:1.1. bIsolated yield. cThe dr value was determined by 1H NMR. dThe er value was determined by HPLC.
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