14. Synthetic Techniques

Using any necessary inorganic reagents, show how you would convert acetylene and isobutyl bromide to

(b) (±)-2,7-dimethyloctane-4,5-diol.

a. Propose a mechanism for the following reaction.

2 (CH₃)₂C=CH–CH₃ + cat. H⁺ → 2,3,4,4-tetramethylhex-2-ene

b. Show the first three steps (as far as the tetramer) in the BF₃–catalyzed polymerization of propylene to form polypropylene.

Suggest a synthetic scheme, involving a protecting group, to generate the molecule shown starting with the molecule at the left.

(c)

Complete each synthesis by providing the structure of the major product at each step, including any important stereochemistry.

b.

c.

d.

Which of the following is the most appropriate first disconnection in the retrosynthetic analysis of ${\mathrm{Ph}}_2\mathrm{CO}$ (benzophenone)?

Which of the following statements best describes the purpose of retrosynthesis in organic chemistry?

Determine the structures of compounds A through G, including stereochemistry where appropriate.

Complete each synthesis by providing the structure of the major product at each step, including any important stereochemistry.

a.

Show how you would synthesize each compound, starting with alkenes or cycloalkenes that contain no more than six carbon atoms. You may use any additional reagents you need.

(c)

For each synthesis, start with bromocyclohexane and predict the products. Assume that an excess of each reactant is added so that all possible reactions that can happen will happen.

(c)

Propose a synthesis of the carbonyl(s) using the (ii) dihydroxylation/periodic acid cleavage pathways.

(a)

Compound A (C₇H₁₁Br) is treated with magnesium in ether to give B (C₇H₁₁MgBr), which reacts violently with D₂O to give 1-methylcyclohexene with a deuterium atom on the methyl group (C). Reaction of B with acetone (CH₃COCH₃) followed by hydrolysis gives D (C₁₀H₁₈O). Heating D with concentrated H₂SO₄ gives E (C₁₀H₁₆), which decolorizes two equivalents of Br₂ to give F (C₁₀H₁₆Br₄). E undergoes hydrogenation with excess H₂ and a Pt catalyst to give isobutylcyclohexane. Determine the structures of compounds A through F, and show your reasoning throughout.

a. Starting with 3-methyl-1-butyne, how can you prepare the following alcohols?

2. 3-methyl-1-butanol

b. In each case, a second alcohol would also be obtained. What alcohol would it be?

Develop syntheses for the following compounds, using acetylene and compounds containing no more than four carbon atoms as your organic starting materials.

(a) 3-methylnon-4-yn-3-ol (“3-ol” means there is an OH group on C3.)

Give the structures of the products represented by letters in this synthesis.

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