Question

Please show the mechanism for the following:

Dipolar orientation OH t-BuMe2Sio OBBu2 tBuMe2Sio Cy Cy t-BuMe,SiO -BuMe2Sio Me Me

Answer 1

The enolisation process occurs via 6-memberedchairtype transition state where the R group is pointing away from the chiral auxiliary group; hence, Z-enolate is favored in this process This favored intermediate implies that the addition can only happen from the frontface Favouret rotamer Z-enolate BU2 H BU Bu B-Bu favored f-BuMe SiO Me aldehyde react with the R group equatorial by steric interactions Bu Bu Bu Bu O OH Syn aldol Me Me Me t-BuMe Sio f-BuMe SiO