UNIT 5 - Enolates-04-aldol in synthesis

UNIT 5 - Enolates-04-aldol in synthesis - SC6POC OMalley...

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SC6POC – O’Malley Enolates 4 Name: __________________ (not in textbook) (Aldols in synthesis) © S. O’Malley 2010 1. Regioselective enolization : Propose a mechanism to explain the different results below. O Me Me Br 1. LDA, -78 o C 2. O Me Me O Me Me Br 1. LDA, RT 2. O Me Me 2. Diastereoselective aldol. Propose a transition state to explain the different results below. O Bu 2 BOTf i -Pr 2 EtN -78 o C O B Bu Bu H O Ph -78 o C O Ph Me OH O Cy 2 BCl Et 3 N -78 o C O B Cy Cy H O Ph -78 o C O Ph Me OH 3. Enantioselective (Evans) aldol : Show ALL possible stereoisomers possible from the following aldol. (there are 4!!) Ph O Me H O + aldol addition 4. Evans aldol – the details: a. Suggest reagents to accomplish the following: NH O O Bn (HINT: most reactive carboxylic acid derivative) (S) - oxazolidinone i. n -BuLi ii. chiral imide i. n -Bu 2 BOTf Et 3 N ii. N O O O Bn Me OH Me N O Me i. Cy 2 BOTf Et 3 N ii. O O Bn N O O O Bn Me OH Me ( anti ) ( syn ) b. Propose a transition state to explain ONE of the observed aldol addition results above.
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UNIT 5 - Enolates-04-aldol in synthesis - SC6POC OMalley...

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