Dolbier HW Solutions 274

Dolbier HW Solutions 274 - The mirror-image chloride, 1 R...

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function must have arisen by oxidation of the @ CH 2 CH ? C(CH 3 ) 2 side chain. Therefore 11.35 Hydroboration oxidation leads to stereospeci f c syn addition of H and OH across a carbon carbon double bond. The regiochemistry of addition is opposite to that predicted by Markovnikov s rule. Hydroboration oxidation of the E alkene gives alcohol A. Alcohol A is a racemic mixture of the 2 S ,3 R and 2 R ,3 S enantiomers of 3-( p -anisyl)-2-butanol. Hydroboration oxidation of the Z alkene gives alcohol B. Alcohol B is a racemic mixture of the 2 R ,3 R and 2 S ,3 S enantiomers of 3-( p -anisyl)-2-butanol. Alcohols A and B are stereoisomers that are not enantiomers; they are diastereomers. 11.36 Dehydrohalogenation of alkyl halides is stereospeci f c, requiring an anti arrangement between the hydrogen being lost and the leaving group in the transition state. ( Z )-1,2-Diphenylpropene must therefore be formed from the diastereomer shown.
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Unformatted text preview: The mirror-image chloride, 1 R ,2 R , will also give the Z alkene. In fact, the reaction was carried out on a racemic mixture of the 1 R ,2 R and 1 S ,2 S stereoisomers. H H C 6 H 5 C 6 H 5 CH 3 Cl S S (1 S ,2 S )-1-Chloro-1,2-diphenylpropane H CH 3 C 6 H 5 C 6 H 5 ( Z )-1,2-Diphenylpropene (90%) NaOCH 2 CH 3 1 1. B 2 H 6 2. H 2 O 2 , HO 2 H 3 C H An CH 3 ( Z )-2-( p-Anisyl)-2-butene (2 R ,3 R) H R R OH H CH 3 H 3 C An (2 S ,3 S) CH 3 An H S S H 3 C OH H An 5 CH 3 O 1 1. B 2 H 6 2. H 2 O 2 , HO 2 H 3 C CH 3 An H ( E )-2-( p-Anisyl)-2-butene 2 R ,3 S 2 S ,3 R H R S OH CH 3 CH 3 H An CH 3 An H R S H OH CH 3 OCH 3 OCH 3 CH 2 CH CH 3 O (C 14 H 20 O 3 ) 2,3,5-Trimethoxybenzoic acid Na 2 Cr 2 O 7 H 2 O, H 2 SO 4 , heat C(CH 3 ) 2 OCH 3 OCH 3 CO 2 H CH 3 O 268 ARENES AND AROMATICITY...
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