4328FinalExam2007 - 1 FINAL EXAM - CHM 4328B Please check...

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1 FINAL EXAM - CHM 4328B Professor: Dr. André Beauchemin Date: Wednesday, April 18, 2007 Time: 3 hours Name: Student #: QUESTION POINTS RESULT 1 20 2 10 3 10 4 10 5 20 6 30 Bonus 10 TOTAL 110 / 110 Please check that your exam contains 13 pages Manage your time: browse the exam first!
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2 1. a) Predict the stereochemical outcome of the following transformations. (12 points/ 2 pts each) 1) i -Pr 2 NLi 2) Me-I 2) 1) -Pr 2 NLi Me Me Me Me O OH Me AcOH, –20 °C NaBH(OAc) 3 CO 2 Me Me N O O O Bn R BocN NBoc O + N B O Ph Ph H Ar + TfOH 20 mol% "catalyst" O 2 N CHO H 2 N OMe + N H CO 2 H H 35 mol% O OH N O O O Bn R + Me 2 AlCl (2 equiv)
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3 b) Provide the product of the following transformations. Specify only the relative stereochemistry where appropriate. (8 points/ 2 pts each) + O 95% ee B Cl 2 (please rationalize reactivity with transition state) N Me + Ph O H N N H O Me Ph Me Me • CF 3 CO 2 H n -Bu 90% ee (please provide reaction name) O N Cr O Me Cl TMSO H O R Me Me 3 mol% 1) 2) TBAF, AcOH (product after 1 will also be accepted) B R 1 R 2 H O 20 mol%
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4 2. Corey's introduction of chiral oxazaborolidine catalysts 1 in the borane-mediated enantioselective reduction of ketones represents an important advance in asymmetric synthesis (Corey & Helal, Angew. Chem. Int. Ed. 1998 , 37 , 1986-2012). (10 points) N B O Ph Ph R H 1 , (R = H or Me) Me O Me OH 0.1 equiv 1 1 equiv BH 3 •THF 97% ee ( R ) Provide a detailed mechanism for the overall transformation in the space below. Use three- dimensional representations to illustrate the absolute stereochemical aspects of the indicated transformation.
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5 3. The Myers pseudoephedrine-derived propionamide 1, upon successive enolization with LiN( i - Pr) 2 (LDA) and alkylation with alkyl halide R–X, affords 2 with high diastereoselection (Myers, JACS 1997 , 119 , 6496).
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This note was uploaded on 01/11/2012 for the course CHM CHM 4328 taught by Professor Andrébeauchemin during the Spring '11 term at University of Ottawa.

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4328FinalExam2007 - 1 FINAL EXAM - CHM 4328B Please check...

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