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4328Midtermexam2009 - 1 MIDTERM EXAM CHM 4328B Please check...

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1 MIDTERM EXAM - CHM 4328B Professor: Dr. André Beauchemin Date: Tuesday, February 24, 2009 Time: 80 minutes Name: Student #: QUESTION POINTS RESULT 1 32 2 15 3 12 4 6 5 27 6 12 TOTAL 104 (4 pt bonus!) / 100 Please check that your exam contains 9 pages Manage your time: browse the exam first!
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2 1. (32 points) Predict the stereochemical outcome of the following transformations. (20 points: 2 pts each) When requested, please also provide a clear 3-D representation of the transition state leading to the observed product. (12 points: 4 pts each) Me Me Me Me O OH Me AcOH, –40 °C NaBH(OAc) 3 m -CPBA I 2 , NaHCO 3 (aq) [Ir(pyr)PCy 3 ] + H 2 OMe Me MeI LiNR 2 t -Bu O O OEt PhMe 2 Si Me B H 3 K Me Me R CO 2 H Me HO HO HN Ph O
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3 HO Me Me C 8 H 17 Br 2 , MeOH 1. BH 3 Provide major TS here: Provide major TS here: n -BuMgBr CH 2 Cl 2 CH 3 O OCH 2 OCH 2 CH 2 OMe H 15 C 7 Provide major TS here: Note: for these two TS, using Nuc is OK! Me OBn Me O 2. NaOH, H 2 O 2 DAE problem 61 H O OSiMe 2 ( t -Bu) SnBu 3 BF 3 •OEt 2
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4 2. (Modified DAE Problem 62) (15 points) a) The following stereoselective hydroboration has been reported by Still ( JACS 1983 , 105 , 2487). Provide the stereostructure of the major product and rationalize the stereochemical outcome with a 3-D structure of the transition state, and keywords outlining its important features. (10 points) 1. 9-BBN, THF 2. NaOH, H 2 O 2 The product ?
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