Asymmetric Michael addition promoted by (R,R)-trans-1,2-diaminocyclohexane in ionic liquids

In tetrafluoroborate based ionic liquids fair yields and enantiomeric excesses up to 91% were obtained in the Michael addition of ethyl cyclohexanone-2-carboxylate to methyl vinyl ketone, using (R,R)-trans-1,2-diaminocyclohexane as chiral auxiliary (37% mol/mol with respect to the donor). The presence of catalytic amounts of metal sources [Ni(OAc)2 · 4H2O, Co(acac)2, FeCl3 · 6H2O, LaCl3, Cu(OAc)2 · H2O] did not improve the activity, and, in some instances, caused a drop of enantioselectivity. Reactions carried out in the absence of any metal and with a Michael donor/diamine molar ratio of 20 allowed us to ascertain that the reaction can be performed catalytically.