Chem 450—Advanced Organic Chemistry Exam 4

8. Give structures illustrating why LDA alone promotes formation of the E-enolate, while
addition of HMPA promotes the formation of Z-enolates (8 points)?
Open TS Li does not bridge
Closed TS - Cyclic
H
O
H
N
O Li
THF
THF
9. Explain why the following reaction does not produce the desired product and suggest a
likely structure for the major product obtained (6 points).
O
+
O
NaOH
CH3 O
H3C CH3 H3C H
EtOH H3C H
O
H
OH O
OH O
H3C H
or
H3C CH3 Aldehyde is much more reactive. Also, no heat so no elimination.
10. The following compound was prepared using a Robinson annulation. Give the
structures of the starting materials (6 points).
O
+
O
KOH
EtOH
O
N
H
O