02Exam3_ans

02Exam3_ans - O O Br t-BuO- K+ t-BuOH Br2 Br MeOH + OCH3 Br...

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O Br t-BuO - K + t-BuOH Br 2 MeOH HO OH + enantiomer HO O V O O O HO O t-Bu (1) Hg(OAc) 2 H 2 O (2) NaBH 4 HO H CH 3 Ph CH 3 Ph HO H 2 SO 4 heat OH OH OH OH OH O H 2 Pd/BaSO 4 quinoline O E2 conditions, need antiperiplanar H Br OCH 3 Br OCH 3 + These are enantiomers. The Ph ring is best able to stabilize + charge, hence this regiochemistry 1) RCO 3 H (makes epoxide) 2) HO - (need trans addition of 2 -OHs) Using OsO 4 gives OH OH HO HO t-BuOH O HO O + CH 2 H Ph Ph CH 3 Only this isomer gives the right regiochemistry + + minor isomer MnO 2 only benzylic -OH will react with this reagent
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Hydroboration of propene gives the following mixture of regioisomers: + HB H H B R R + B R R 70% 30% Hydroboration of methyl vinyl ether gives the following mixture of regioisomers: O + H H O B R R + B R R O 95% 5% Explain the greater regioselectivity in the reaction of methyl vinyl ether. The oxygen-substituted ether, a vinyl ether, has a resonance form that places negative charge on carbon 2: O CH 3 H 2 C O CH 3
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This note was uploaded on 05/17/2008 for the course CHEM 0350 taught by Professor Suggs during the Spring '08 term at Brown.

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02Exam3_ans - O O Br t-BuO- K+ t-BuOH Br2 Br MeOH + OCH3 Br...

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