Proline induces the enantioselectivity of the title reaction in an aldol reaction and not in a conjugate addition. This was demonstrated by the two following sets of experiments.(i) Recovered keto sulfides 4 and 5 did not show any optical activity when the racemic substrates were treated with (S)-proline; moreover (S)-proline was unable to induce chirality during the conjugate addition of thiophenol on cyclohexenone.(ii) Kinetic resolution of ...
