CHEM 332. Spring 2014
Problem Set 4
Prof Donald Watson
1. The Witting reaction is useful for placing double bonds in less stable positions. For example,
the following transformation is easily accomplished using a Witting reaction.
O
CH 2
(a) Show how you would use a Witting reaction to do this.
(b) Show how you might do this without using a Wittig reaction, and explain why the Wittig
reaction is a much better synthesis.
2. Predict the product for the following Wittig reactions with arrow-pushing mechanism. Please
do not ignore stereochemistry.
O
benzene
H
Ph 3P CHCH3
H
Ph 3P CHCO 2Et
O
ethanol
O
benzene
Ph 3P CHCH 2CH 2CH3
O
ethanol
Me
3.
Ph 3P CHCN
The Baeyer-Villiger oxidations of the substituted diphenyl ketones proceeds as indicated.
Please rationalize this result using mechanism.
O
OMe
OMe
O
m-CPBA
O
CHCl3
NO 2
O
O
m-CPBA
NO 2
CHCl3
O
4. Predict the product for the following Baeyer-Villiger Oxidation with arrow-pushing mechanism.
O
O
Me
O
Me
Me
Me
Me
Me
CF3COOOH
CF3COOOH
Me
CF3COOOH
O
H
CF3COOOH
5. Complete the following equilibria, show all products. Using your knowledge of pka’s predict
the equilibrium constant for each reaction. In all cases please draw the expected product, even if
the reaction is highly endothermic.
O
HCl
O-
Me
Na +
K eq =
LDA
EtOH
K eq =
NaOH
BuOH
K eq =
EtONa
Ph
H
K eq =
O
Et 3N
K eq =
6. Propose a mechanism for the following reaction:
O
O
O
HO EtOH
O
7. Starting from cyclohexanone, How would you synthesis the following compounds using Stork
enamine synthesis.
O
O
O
O
OEt
Me
O
O
CN
Ph
O
8. Predict the product with arrow-pushing mechanism.
1. LDA, -78 °C
THF
O
Me
2. CH3CH 2Br
O
NaOH/H 2O
Δ
O
O
O
Me
O
Excess I 2, NaOH
1. (CH 2=CH) 2CuLi, THF
2. CH 2=CHCOCH3
O
LDA, -78 °C
THF
Me
Br
1. LDA, -78 °C
THF
O
2. BrCH 2CO 2CH3
O
Excess Br 2, NaOH
H
2
NaOH/H 2O
O
9. The following sequence of reaction is called as Robinson Annulation. It is one of the
methods for building substituted cyclohexenones and this synthetic strategy was used in
several complex natural product syntheses. Identify products A and B.
O
Me
Me
O
NaOEt/EtOH, -10 oC
A
NaOH/H 2O
Δ
B
10. Show how you might carryout the following synthetic transformation:
O
O
Me
Me
11. Please draw a arrow-pushing mechanism for the following reactions.
Me
N
O
Me
Δ
Me
OMe
Me
Δ
NH 3
OEt
MeOH
O
HCl/H 2O
OMe
OH
O
HCl/EtOH
O
Me
O
NaOH/H 2O
Me
OH
MeOH