Chem 331
Exam 3
December 6, 2002
Prof. Fox
50 minutes
The exam is open book,
Open notes. Models are permitted
Show your work in detail
WRITE YOUR NAME ON EVERY PAGE
NAME
KEY
Chem 331, Exam 3. December 6, 2002
NAME
(25 pts)
1. Draw the structures of A and B. You do not need to provide mechanisms
OH
DCC, Et3N
+
O
1) O3
A
B
2) (CH3 )2S
N
H
N
N
O
O
O
A
B
2. The reactions below would not proceed as shown. Explain why (be concise), and indicate which product
would be formed instead.
OH
HO
1) MeLi (2 equiv)
O
O–
–O
O
(20 pts)
2) H+
This substrate has 2 hydroxyls, so the MeLi is completely comsumed by deprotonating the two
hydroxyls. Addition of acid regenerates the starting material.
Chem 331, Exam 3. December 6, 2002
NAME
2 (continued). The reactions below would not proceed as shown. Explain why (be concise), and indicate which
product would be formed instead.
b.
OH
H2CrO4
O
X
(20 pts)
H2SO 4
H2O, acetone
O
OH
overoxidizes to the acid
c.
H
D
H2
D
Pd/C
D
Me
H
D
Pd catalyzed hydrogenation occurs by cis-addition across the
double bond. The product above is that of trans addition.
either of the enantiomers below were accepted
H
D
D
H
Et
Et
H
D
D
H
Me
Me
Et
(25 pts)
Chem 331, Exam 3. December 6, 2002
NAME
3. Propose a synthesis for 1 starting with any materials that contain 3 carbons or less. You may also use reagents
that contain more than 3 carbons (e.g. BuLi, Ph 3P, LDA, MCPBA, DIBAL, DCC, pyridine, TsCl, NaOtBu, Et3N).
However, Grignard and Wittig reagents must be prepared.
(40 pts)
O
1
CH3 I
1) PPh 3
2) NaOtBu
O
PPh3
NBS
Mg
Br
hν
MgBr
1) BuLi
CN
2)
Br
1) combine
CN
one possible answer
2) H3O+
O
Chem 331, Exam 3. December 6, 2002
NAME
4. Propose the structure of 2 (10 points). Explain how the spectroscopic data helped you make your
stereochemical assignment. (25 points).
1)
+
Ph3P
CO2Me
2
2)
Br
O
–
13
1
167.3, s
144.8, d
134.5, s
130.2, d
128.9, d, 2 carbons
128.8, d, 2 carbons
117.9, d
51.5, q
7.67 (1H, d, J= 15.8 Hz)
7.6–7.2 (m, 5H)
6.40 (d, 1H, J=15.8 Hz)
3.80 (s, 3H)
C NMR
ONa
C10H10O2
H NMR
10 points for connectivity
25 points:
H
O
O
15.8 Hz coupling constant indicates that this is a
trans alkene
H
(35 total pts)
Chem 331, Exam 3. December 6, 2002
NAME
(35 pts)
5. Propose a detailed mechanism for the rearrangment below
X–
H+
H+
X–
H
X–
X–