chem 330 final exam december 19, 2005chem 330 final exam december 19, 2005 your name: this a...
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CHEM 330
Final Exam December 19, 2005
Your name:
This a closed-notes, closed-book exam
The use of molecular models is allowed
This exam contains 12 pages
Time: 2h 30 min 1. ________ / 24 2. ________ / 24 3. ________ / 22 4. ________ / 40 5. ________ / 40 6. ________ / 40 7. ________ / 50 8. ________ / 60 TOTAL ________ / 300 = ________ / 100
This exam counts for 45% of your CHEM 330 final grade
Chem 330 final exam p. 2 of 12 1. (24 pts.) Indicate the approximate pKa's for the ionization of the protons in boldface in the following molecules (write your answer in the box):
OH
EtO HNH
O
OEtH
approx.pKa =
O O
OEtH
H–H
O
O HH
approx.pKa =
2. (24 pts) Check the appropriate box to indicate whether the following transformations involve overall oxidation, reduction, or neither, of the starting compound:
O OOTMS
oxid. redn. neith.
O
O OTMSO
O
OH
O
OH
a. b.
OHe.
c.
oxid. redn. neith.
oxid. redn. neith.
d.
oxid. redn. neith.
f.
oxid. redn. neith.oxid. redn. neith.
BH2
O
OEt
Og.
oxid. redn. neith.
O
OEt2h.
O
Ph
O
OPhoxid. redn.neith.
Chem 330 final exam p. 3 of 12 3. (22 pts.) Write detailed mechanisms for the following known reactions:
TBS-OTf
Et3NOMeOOC
NCa. OTBS
COOMe
CN
b.OMe
COOMe
1. LDA, then TMS-Cl
2.
heat3. TBAF, then aq. wrkp.
COOMe
OMe
OHCOOMe
Chem 330 final exam p. 4 of 12 4. (40 pts.) Write a chemical equation to show an example of the following reactions encountered in class (do not write mechanisms – just the reactions): Prasad reduction: Cannizzaro reaction: Robinson annulation: Miller silyl enol ether synthesis:
Chem 330 final exam p. 5 of 12 5. (40 pts) Check the appropriate box to indicate whether the following statements are true or false.
a. The copper atom undergoes reductive elimination in the following reaction:
Me2CuLi + 2 HBr 2 Me–H + LiBr + Cu–Br
true false
b. The following transformation may be induced by the use of Me2CuLi:
Cl
O O
true false
c. Treatment of A with metallic Na, followed by aqueous workup, will result in formation of B:
COOEtCOOEt O
OH
metallic Na,
then aq. wrkp.A B
true false
d. The reaction shown below will give compound C as the major product:
COOEtCOOEt NaH,cat. EtOH
then aq. wrkp.C
O
COOEt
true false
e. The reaction shown below is a reverse Diels-Alder:
H
H
NCNC
NCNCH
H
H H
true false
Chem 330 final exam p. 6 of 12
f. Treatment of D with NaBH(OAc)3 followed by aqueous workup yields E as the major product:
Ph
OOH
Ph
OHOHNaBH(OAc)3
then aq. wrkp.D E
true false
g. Treatment of F with catalytic NaOMe will cause isomerization to G:
H
H
O H
H
O
F G
cat. NaOMe
true false
h. The following sequence represents a good method for the preparation of H:
H
O
H
1. LDA
2. Et–I H
O
true false
i. Substrate and reagent in the reaction shown below are stereochemically mismatched:
N OMeO OBBu Bu
PhMeO H
CHO+
MeO H
OH
Me
O
Xc
true false
j. Compound I shown below is the product of an endo-Diels- Alder reaction:
H
O
OMe
I
true false
Chem 330 final exam p. 7 of 12 6. (40 pts.) Predict the structure of the major product expected from the following reactions. Note: It is not necessary to draw mechanisms.
ON
OO
Me Ph
1. LDA2. BnBr
3. K2CO3 MeOH
a.
1. CH2=CHCu(PBu3)2
2. Bu–I, then aq. wrkp.
O
b.
heatc. COOMe
Ph
O
OMe
1. LDA, THF - HMPA
2. CHO
OTBS
d. then aq. wrkp.
COOMee.
1. Cy2BCl Et3N
2.f. Ph
O
Ph CHO
OMe
O
1. excess NaH, cat.EtOH, 1 eq.
(EtO)2CO2. CH2=CH-CH2Br3. Aq. wrkp.
g.
OMe
CHOON
OO
Bn
1. Bu2BOTf, Et3N
2.h.
then aq. wrkp.
Chem 330 final exam p. 8 of 12 7. (50 pts.) Indicate a method to accomplish the transformations shown below. In each case, a multistep sequence (= not just one reaction, but several) may be necessary. Assume the availability of all required reagents (e.g, bases, alkyl halides, etc.). Present your answer as a flowchart. Note: It is not necessary to draw mechanisms.
a.OO
OHPh
O
OEt
O O
b.
(racemic)
O OTBS
c.
Me
HO
Me
HO
Chem 330 final exam p. 9 of 12
O
O
OMe
OMe
Od.
TBSO
e.O MeH
OH
Me
OHH
H
(this enantiomer)
Chem 330 final exam p. 10 of 12 8. (60 pts) Propose a method to achieve the enantioselective synthesis of the molecules shown below. Be careful about protecting groups and relative/absolute configurations of stereocenters. Assume the availability of all required reagents, chiral auxiliaries, etc.
a. starting withOTBS
I
OTBS O
N O
O
Bn
andOTBS
COOEt
Chem 330 final exam p. 11 of 12
b. starting withO
H
TBSOOHHO O O
DD
Chem 330 final exam p. 12 of 12
c. starting withO
Cl
O
MePh
O
OH
Me
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