14. Synthetic Techniques

Show how you would synthesize the following compound. As starting materials, you may use any alcohols containing five or fewer carbon atoms and any necessary solvents and inorganic reagents.

When doing synthesis, you will often find yourself repeating the same series of steps. To see this in action, synthesize the following aldehydes beginning with an organic molecule containing three carbons or fewer.

(b)

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

(a)

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.

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.)

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

(b) cis-1-ethyl-2-methylcyclopropane

Propose mechanisms to explain the opposite regiochemistry observed in the following two reactions.

Show how you would accomplish the following synthetic conversions.

(c) 2−methylcyclohexanol → 1−bromo−1−methylcyclohexane

Work backward to show how the cyclopropane would be synthesized from the chloroalkane shown.

For each of the following target molecules, design a multistep synthesis to show how it can be prepared from the given starting material:

b.

Identify A–E.

Using cyclooctyne as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.)

(h)

For each of the following target molecules, design a multistep synthesis to show how it can be prepared from the given starting material:

a.

A, a compound with molecular formula C₆H₁₀, contains three methylene units. A reacts with one equivalent of H₂ over Pd/C to yield B. A reacts with aqueous acid to form a single product, C, and undergoes hydroboration/oxidation to form a pair of enantiomers, D and E. Ozonolysis of A followed by reaction with dimethyl sulfide forms F with molecular formula C₆H₁₀O₂. Provide structures for A–F.

Starting with cyclohexene, how can the following compounds be prepared?

c. dicyclohexyl ether