Initials______________
Chemistry 634, Fall 2012
Final Exam
Prof. Donald Watson
300 points (2 hours)
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Closed note, closed book. No calculators allowed. You may use a molecular
model set.
Answers should be written in boxes provided. Other markings will not be
considered. Scratch paper can be found at the back of the exam packet.
Please initial each page at the top.
Points will only be awarded for clearly communicated answers.
Please make sure you have all pages of the exam packet (12 pages).
Name _______________________________________
Question 1: ________/50
Question 2: ________/60
Question 3: ________/40
Question 4: ________/50
Question 5: ________/50
Question 6: ________/50
_____________________
Total:_______/300
Page 1/12
Initials______________
1) (50 points, 10 points each) Predict the expected major product for each reaction
sequence after aqueous work-up, drawing your answer in box provided. Denote
stereochemistry where needed. If no reaction is expected, state so.
1) TIPSOTf, 2,6-lutidine
2) BH3, then NaOH/H2O
3)
AcO OAc
I OAc
O
OH
H
H
OTBDPS
tBuO
O
AcO
O
Bu
O
2C
O
H2 (45 psi), 10% Pd/C
MeOH
CO2tBu
N3
AcO
OAc
1) LAH
2) NaH, CS2, MeI
3) Bu3SnH, AIBN
O
BnO
Me
nBu
2BOTf,
iPr
2NEt;
Me
O
O
O
O
Me
Me
N
then
H
Bn
O
Cl
O
N
O
Cl
O
O
Me
Me
Cl
O
O
O
Me
O
Me
N
Zn, NH4OAc
S
Me
Me
Me
_______/50 points
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Initials______________
2) (60 points)
A) In the spaces below, provide the missing reagents and intermediates needed to
complete the synthesis. Note: More than one step or reagent may be required over
each arrow.
5 pt
5 pt
Cl
ClMg
Me
Me
O
5 pt
Me
Me
Me
OTMS
LDA, THF, -78 °C
Me
OTMS
A
then
O
H
Cl
B
O
OH
C
5 pt
TBAF, THF
Me
OTMS
D
Cl
5 pt
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Initials______________
B) (5 points) In the above scheme, the formation of intermediate B involves the use of
“LDA”. Please provide the structure of LDA below.
C) (10 points) Considering the scheme above, in the space below, please provide a
model that accounts for the formation of intermediate B.
D) (5 points) Is the structure of intermediate B best described by a kinetic or
thermodynamic model? Please explain using the space below.
E) (10 points) In the space below, please provide a model that accounts for the
stereochemistry observed in the formation of compound D.
______/60 points
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Initials______________
3) (40 Points)
A) In the spaces below, provide the missing reagents and intermediates needed to
complete the synthesis. Note: More than one step or reagent may be required over
each arrow.
Me
Me
TMSO
OH
10 pt
O
H
OTIPS
don't worry about
stereochemistry for
this step
Me
1) NaBH4, MeOH, –78 °C
2) TBSCl, imid
OH
TBSO
H
OTIPS
OTIPS
E
Me
F
O
LiB(sBu)3H, THF
10 pt
TBSO
> 95:5 dr
H
Me
TBSO
OH
H
OTIPS
G
H
> 95:5 dr
OTIPS
H
B) (10 Points) In the space below, please rationalize the stereochemistry observed in
the conversion of E to F. Recall only clearly communicated answers will receive credit.
C) (10 Points) In the space below, please rationalize the stereochemistry observed in
the conversion of G to H. Recall only clearly communicated answers will receive credit.
______/40 points
Page 5/12
Initials______________
4) (50 points, 5 points each) Please provide the homolytic bond strengths (BDE’s) for
the indicated bonds. Only answers within 3 kcal/mol of the actual value will be given
credit.
Bond
BDE (kcal/mol)
Me-H
iPr-H
tBu-H
RO-H
CH2=CH-H
HOCH2-H
MeC(O)CH2-H
Et-Cl
C≡C (triple)
C=O (double)
______/50 points
Page 6/12
Initials______________
5) (50 points)
A) (30 points) Please provide a complete and detailed mechanism for the conversion of
I to J in the space below.
Me
Me
OH O
Me
N
Me
O
I
1) DIBAL-H
2)
OEt
EtO
OEt
, NaH
P
O
O
Me
OEt
Me
OH J
O
Page 7/12
Initials______________
B) (20 points) In the space below, please provide a model that explains the alkene
geometry of product J.
______/50 points
Page 8/12
Initials______________
6) (50 points) In the space below, propose a synthesis of K using 1,3-cyclohexadione
and any other reagents that you require.
O
Me
Me
O
Me
K
______/50 points
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Initials______________
This page provided for scratch paper. No answers on this paper will be graded.
Page 10/12
Initials______________
This page provided for scratch paper. No answers on this paper will be graded.
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Initials______________
This page provided for scratch paper. No answers on this paper will be graded.
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