CHEM 330. Final Exam December 11, This a closed-notes, closed-book exam. The use of molecular models is allowed. This exam contains 12 pages

Transcription

1 CEM 330 Final Exam December 11, 2007 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. / / / / / / / / 40 TTAL / 250 = / 100 This exam counts for 45% of your CEM 330 final grade

2 Chem 330 final exam p. 2 of (20 pts.) Write a chemical equation to show an example of the following reactions (do not write mechanisms just the reactions). a. Baylis-illman reaction: b. Prasad Reduction: c. Cannizzaro reaction: d. Mukaiyama aldol reaction: e. Swern oxidation:

3 Chem 330 final exam p. 3 of (20 pts.) A highly stereoselective reaction ensues when compound A below is treated with 1 equivalent of ZnCl 2, followed by cyclopentadiene. The result is product B. (i) Draw the structure of B in the box; (ii) Sketch an approximate transition state structure that accounts for the observed stereoselectivity. ZnCl 2, then A N cyclopentadiene approximate transition state structure: B

4 Chem 330 final exam p. 4 of (30 pts.) Complete the reaction diagram shown below by indicating all missing reagents / products. Each box corresponds to one reagent / product. Note: aqueous workup steps are understood and are not to be included in your answers. 1. Et CEt C 2. (together) excess CEt CN and N (together) (together) A 1. TBAF CEt heat 2. and N (together) CN final product B

5 Chem 330 final exam p. 5 of (40 pts) Check the appropriate box to indicate whether the following statements are or. a. The copper atom undergoes reductive elimination in the following reaction: 2 CuLi + 2 Br 2 + LiBr + Cu Br b. The following transformation may be induced by the use of MgBr: Cl c. Treatment of A with Li and tert-bu in liquid N 3, followed by allyl bromide, results in formation of B: Li, tert-bu A liq. N 3, then C 2 =C-C 2 Br B d. The reaction shown below will give compound C as the major product: CEt CEt Na,cat. Et then aq. wrkp. C CEt e. The reaction shown below is a retro-diels-alder: NC NC NC NC

6 Chem 330 final exam p. 6 of 12 f. Treatment of D with NaB(Ac) 3 followed by aqueous workup yields E as the major product: NaB(Ac) 3 then aq. wrkp. D E g. Reaction of F with Na yields compound G: cat. F Na G h. Compound may be converted to I as follows: 1. LDA 2. -C 2 Br I i. Substrate and reagent in the reaction shown below are stereochemically matched: C + Bu B Bu N Xc j. Compound J forms when 1,3-cyclohexadiene reacts with maleic anhydride: J

7 Chem 330 final exam p. 7 of (30 pts.) Provide a succinct explanation for the following experimental observations: (a) Benzoquinone A undergoes Diels-Alder reaction with butadiene selectively at the methyl-substituted double bond, because: A (b) The Noyori copper reagent shown below adds stereoselectively to enone B to form C, Cu(PBu 3 ) 2 because: B then aq. workup C (b) Reaction of ketone D with a defect of LDA produces enolate E, 0.9 equiv. of LDA because: D Li E

8 Chem 330 final exam p. 8 of (40 pts) Predict the structure of the major product expected from the following reactions. Notes: (i) it is not necessary to draw mechanisms; (ii) aqueous workups at appropriate stages are understood. 1. LDA, TF a. 2. TBS C b. Bn N 1. LDA 2. C 2 =CC 2 Br 3. K 2 C 3 c 1. Cy 2 BCl Et 3 N 2. C 3. NaB(Ac) 3 1. LDA, TF - MPA d. Et 2. C e. N 1. Bu 2 BTf, Et 3 N 2. C

9 Chem 330 final exam p. 9 of 12 f BBN-Tf Et 3 N 2. C 3. NaB(Ac) 3 g. 1. excess tbuk, 1 equiv. of EtC-CEt 2. N 2 N N 2 h. 1. LDA, then SeBr 2.MCPBA, then heat 3. 2 CuLi, then Et 3 N and Br i. CEt 1. Na, cat. Et 2., cat. DBU CEt 3. tbuk j. 1. C 2. excess C, aq. Na

10 Chem 330 final exam p. 10 of (30 pts.) Indicate all the reagents that are necessary to effect the following transformations. Provide your answers as a numbered list of reagents, in the correct order, written over/under the reaction arrows, according to the format of question 6 above. a. C b. c. d. CEt CEt CEt e. CEt (racemic) f. C (racemic) g. CEt

11 Chem 330 final exam p. 11 of (40 pts) Propose a method to achieve the enantioselective synthesis of the molecules shown below starting with the indicated building blocks. Be careful about protecting groups and configurations of stereocenters. Assume the availability of all needed reagents, auxiliaries, etc. Present your answer as a flowchart. It is not necessary to draw mechanisms. from: C a.

12 Chem 330 final exam p. 12 of 12 b. TBS -Si(iPr) 3 from: I -Si(iPr) 3 (cf. J. rg. Chem. 2006, 71, 9853) appy olidays!