final_exam_f2016_done.pdf Chem 234: Final Exam December 8, 2016 Name: Student ID number: Discussion TA: Discussion day and time: Seat Number: (1) Put your final answer in the box, when provided, to...

final_exam_f2016_done.pdf
Chem 234: Final Exam
December 8, 2016

Name:

Student ID number:

Discussion TA:

Discussion day and time:

Seat Number:

(1) Put your final answer in the box, when provided, to obtain full credit.
(2) Please turn off any electronic devices.
(3) People caught using electronic devices will have their exams confiscated.



GOOD LUCK!










Point total:

Question 1 (35 pts):
Question 2 (35 pts):
Question 3 (20 pts):
Question 4 (40 pts):
Question 5 (30 pts):
Question 6 (15 pts):

TOTAL POINTS:
Out of 175 pts

1

1. (35 points) Predict the products and indicate the relative stereochemistry for the following transformations.
When necessary indicate the major product.

(a) (5 points)



(b) (5 points)




(c) (5 points)




1.
2. NaBH3CN, HOAc
O
H
H2N
Me
Me
1.H3O+, heat
3. H3O+H
H
Me
H
Me
OMeMe
H
O
O
2. PhMgBr, Et2O
1.Br2, FeBr3
2. BrMg
F
cat. Pd(PPh3)4, THF
OMe
OMe
2

(d) (5 points)




(e) (5 points)



(f) (5 points)





1. NaOMe, HOMe
O
MeO
Et
OMeO
2. H3O+, heat
1.NaOMe, HOMe
O
Me
CF3
Br Ph
2.
H2N
H
N
MeMeOH, H+
3. xylenes, heat
1.
2. cat. (Ph3P)3RhCl, H2
CH2Cl2
Me
Me toluene, heat
CNNC
3

(g) (5 points)










1. LiAlH4, Et2O
4.
2. H3O+
O
O
3. PCC, CH2Cl2
Ph3P CH2 , THF
5. PCy3
Ru
PCy3
Ph
Cl
Cl
(2 mol %)
CH2Cl2
4

2. (35 points) Provide the necessary reagents to accomplish the desired organic reactions. Please number
the steps and note that some reactions will require more than one step.
(a) (5 points)


(b) (6 points)

O
O
O
O
O
OH
Me OHMe
5

(c) (6 points)




(d) (6 points)




OMe
OO
n
OMe
OMe
O
H
HN
NH3
HN O
O
6

(e) (6 points)



(f) (6 points)



Et
Et
Et
Et
CO2Me
O
Et
Me
OHO
Cl Me
7

3. (20 points) Perform the two retrosynthetic analyses given below.

a) (10 points)




1.
2.
3.
8.
6.
7.
4.
O
O
O
O
Br
5.
Ph
OCl
8

(b) (10 points)



1.
2.
3.
4.
5.
7.
6.
6.
H
N
O
OEt
O
N
O
Me
OMeOO
Ph
9

4. (40 points) Please provide a detailed arrow pushing mechanism for the following transformations.
(a) (6 points)





O
HMe
Me
H
HO OH
Me
MeH2O
10

(b) (8 points)












O
Cl
OMe
O
OMe
O
Mepyridine
HO
Me
11

(c) (8 points)


N
H N
O
OH
OH
Me
O3PO
-2
t-Bu
N
H N
OH
Me
O3PO
-2
t-Bu
+ CO2
amino acid decarboxylase
12

(d) (10 points)



O
OHHN
i-Pr
OOPh O
OH2N
S
O
O
H
NN
H
i-Pr
SO
O
O
Ph
N • N
+
13

(e) (8 points).



PCy3
ligand
dissociation
Cy3P
Ru
PCy3
Cl
[2+2]
retro
[2+2]
Ph
olefin
coordination
olefin
coordination
Cy3P
Ru
Cl
Ph
Cl
Cl
14

5. (30 points) Intra- and Intermolecular interactions that control reactivity and structure.

(a) (8 points) Consider the following aldol reaction.





Fill in the substituents in the lowest energy chair transition state that explain the stereoselectivity in the
deprotonation (step 1).






EtO
Me
O 1. LiN(iPr)2, THF, –78 °C
2. PhCHO
3. H4NCl (aq soln)
EtO Ph
O
Me
OH
O
Li
H
15

Fill in the substituents in the lowest energy chair transition state that explain the stereoselectivity in the enolate
addition to the aldehyde (step 2).





O O
Li
EtO
16

(b) (5 points) Provide the chair transition state for the following acid-catalyzed cyclization.












(c) (5 points) Provide the chair transition state to explain the diastereoselectivity in the following Claisen
rearrangement.









O
Me
Me
Me
HO
Me
H
H+
xylenes
heat
O
HPhO
Me
Me
Ph
17

(d) (7 points) Consider the following glycosylation reaction.





(a) (3 points) Draw a three-dimensional representation of the oxocarbenium intermediate.





(b) (4 points) Illustrate the transition state that leads to:





O
BnO
OAc
OAc
BnO NaCN, H+
BnO
O
BnO
OAc
CN
BnO
BnO
O
BnO
OAc
BnO
BnO CN
H
H
+
O
BnO
OAc
BnO
BnO CN
H
18

(e) (5 points) Consider the following nucleotide base pairs.



Illustrate the hydrogen-bonding that occurs between two matched base pairs in a double-stranded RNA ladder-
structure.

N
NN
N
H
NH2
N
NHN
N
H NH2
O
HN
N
H
O
Me
O
HN
N
H
O
O
N
N
H
O
NH2
19

6. (15 points) Spectroscopy

(a) (5 points) Predict the product for the reaction given below.



(b) (3 points) For the 1H NMR spectrum illustrated below, label each of the indicated peaks with the appropriate
functional group.



List of 1H NMR resonances: 9.9 ppm (singlet, 1H), 7.7 ppm (doublet, 2H), 6.9 ppm (doublet, 2H), 3.7 ppm
(singlet, 3H).

3.
Cl Cl
O
O , DMSO
Et3N, CH2Cl2
MeO
1. PhMgBr, Et2O
2. H3O+
H
O
20

(c) (2 points) For the 13C NMR spectrum illustrated below, label each of the indicated peaks with the
appropriate functional group.


List of 13C NMR resonances: 190 ppm, 164 ppm, 132 ppm, 130 ppm, 114 ppm, 55 ppm.


21

(d) (2 points) For the IR spectrum illustrated below, label each of the indicated peaks with the appropriate
functional group.



(e) (2 points) Draw the structure of the compound represented by the spectra given above in the box given
below.











(f) (1 point) Which reaction failed in the three-step sequence?







The spectra for this problem were reproduced from the National Institute of Advanced Industrial Science and
Technology, http://riodb01.ibase.aist.go.jp/sdbs/ on December 7, 2015.
22
May 05, 2021

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