When 1,2-dimethylcyclopentene undergoes hydroboration–oxidation, one diastereomer of the product predominates. Show why this addition is stereospecific, and predict the stereochemistry of the major product.
Show how you would accomplish the following transformations.
(c) 1-methylcycloheptanol → 2-methylcycloheptanol
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Concetti chiave
Nucleophilic Substitution
Stereochemistry
Rearrangement Reactions
When (E)-3-methylhex-3-ene undergoes hydroboration–oxidation, two isomeric products are formed. Give their structures, and label each asymmetric carbon atom as (R) or (S). What is the relationship between these isomers? What is the relationship between the products formed from (Z)-3-methylhex-3-ene and those formed from (E)-3-methylhex-3-ene?
When HBr adds across the double bond of 1,2-dimethylcyclopentene, the product is a mixture of the cis and trans isomers. Show why this addition is not stereospecific.
Show how you would accomplish the following transformations.
(a)
Give mechanisms to account for the stereochemistry of the products observed from the addition of bromine to cis- and trans-but-2-ene (Figure 8-5). Why are two products formed from the cis isomer but only one from the trans? (Making models will be helpful.)
Show how you would accomplish the following transformations.
(b)
