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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