Conjugate addition of reagent 1A to 2-cyclohexenone 3 can be realized in THF-HMPT, so that one-pot conjugate addition—CH 3I enolate trapping, leading to trans 2-methyl 3-benzoylcyclohexanone 17 can be easily performed. From isophorone 4 and Δ 1(9)-2-octalone 5, 1, 4-addition under kinetic control is observed in THF. In the presence of HMPA, the reaction is under thermodynamic control. At low temperatures enolate 19a is in equilibrium with 1A and 4; from 4 at 0° or 5 at −65° or at 0°, the equilibrium lies on the side of starting materials. No reaction between 1A and 6 takes place in any solvent. The reaction of 1B and isophorone 4 in THF leads to 1, 2-addition under kinetic control and to 1, 4-addition under thermodynamic control. In THF-HMPT, retro-Michael addition is observed. However, 1, 2-addition takes place in THF to 6. The different results are interpreted in terms of interplay of ion-pairing, steric decompression and steric hindrance to 1, 4-addition as well as the possibility of participation of the Li cation for 1, 2-addition.