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. 2013 Jun 24;9:1210–1216. doi: 10.3762/bjoc.9.137

Table 5.

Asymmetric tandem Friedel–Crafts alkylation/Michael addition reaction of nitroolefin enoates with indoles.

graphic file with name Beilstein_J_Org_Chem-09-1210-i005.jpg
entrya R1 R2 R3 R4 product Yield (%)b drc ee (%)c,d
1 H H H H 3a 88 92:8 92/88
2 H H H CH3 3b 88 44:56e 62/98
3 H H H OCH3 3c 96 28:72e 73/99
4 H H H Cl 3d 58 76:24 82/53
5 H H CH3 H 3e 89 82:18e 65/79
6 H Cl H H 3f 86 74:26 95/95
7 H Br H H 3g 100 60:40 91/93
8 H NO2 H H 3h 89 49:51 95/95
9 OCH3 H H H 3i 85 58:42e 39/83
10 OC2H5 H H H 3j 94 54:46e 30/97
11 Br Br H H 3k 75 38:62 53/90

aReaction conditions: nitroolefin enoate 1a (0.2 mmol) with indole 2a (0.3 mmol) in 3 mL of toluene catalyzed by 10 mol % ligand-Zn(OTf)2 complex for 72 h at –10 °C. Subsequently, 5 equiv of Et3N was added. bIsolated yields by column chromatography. cDetermined by HPLC. dee for both diastereomers. eDetermined by the weight ratio of isolated diastereomers.