10. Addition Reactions

What stereoisomers are obtained from hydroboration–oxidation of the following compounds? Assign an R or S configuration to each asymmetric center.

c. cis-2-butene

Which is more highly regioselective: reaction of an alkene with BH₃ or with 9-BBN?

Predict the major products of the following reactions, and give the structures of any intermediates. Include stereochemistry where appropriate.

(c)

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?

Predict the major products of the following reactions. Include stereochemistry where applicable.

(c)

Predict the major products of the following reactions. Include stereochemistry where applicable.

(b) trans-4,4-dimethylpent-2-ene + BH₃⋅THF then H₂O₂, OH^–

Predict the major products of the following reactions. Include stereochemistry where applicable.

(a) 1−methylcyclohexene + BH₃⋅THF then H₂O₂, OH^–

Show how you would accomplish the following synthetic conversions.

a. but-1-ene → butan-1-ol

Predict the major products of the following reactions.

(c) 2-methylpent-2-ene + BH₃⋅THF

(d) the product from part (c) + H₂O₂/OH⁻

Predict the major products of the following reactions.

a. propene + BH₃⋅THF

b. the product from part (a) + H₂O₂/OH⁻

Show how you would make the following compounds from a suitable cyclic alkene.

(e)

Show how you would accomplish the following transformations.

(b)

Suggest an alkene to undergo hydroboration–oxidation (1. BH₃ 2. NaOH, H₂O₂) to give exclusively the alcohols shown. Pay close attention to the relative (but not absolute) stereochemical outcome.

(d)

Predict the product(s) that would result when the alkenes shown here are allowed to react under the following conditions: (vi) 1. BH₃ 2. H₂O₂, NaOH

(b)

Predict the product(s) that would result when the alkenes shown here are allowed to react under the following conditions: (vi) 1. BH₃ 2. H₂O₂, NaOH

(g)