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. Author manuscript; available in PMC: 2015 Oct 24.
Published in final edited form as: Chem Sci. 2014 Dec 19;6(2):1537–1547. doi: 10.1039/c4sc02402h

Table 1.

Solvent screen for cyclopropenimine-catalyzed enantioselective Michael reaction.a

graphic file with name nihms730451u1.jpg
entry solvent ε time(h) yield (%) ee (%)
1 1,4-dioxane 2.3 8 95 98
2 PhMe 2.4 5 95 99
3 NEt3 2.4 6 95 99
4 Et2O 4.3 2 95 98
5 EtOAc 6.0 2 86 98
6 THF 7.5 24 95 89
7 CH2Cl2 9.1 10 95 86
8 1,2-F2-C6H4 14.3 4 95 89
9 n-BuOH 17.5 24 45 55
10 acetone 21 1.5 95 80
a

Conversion determined by 1H NMR based on Bn2O standard. Enantiomeric excesses (ee) were determined by chiral HPLC. ε: dielectric constant.