Question

CC(C)(O)CC Oblivon Propose a synthesis for this compound starting with a… # Following is the structural formula of the tranquilizer meparfynol (Oblivon). C#CC(C)(O)CC Oblivon Propose a synthesis for this compound starting with acetylene and a ketone. (Notice the \(-y n\) - and \(-o l\) in the chemical name of this compound, indicating that it contains alkyne and hydroxyl functional groups.)

Short answer

Answer: The correct order of steps for the synthesis of Oblivon (meparfynol) is as follows: 1. Selecting the appropriate ketone (2-pentanone) 2. Hydroboration-oxidation of 2-pentanone with diborane and hydrogen peroxide 3. Conversion of acetylene to propyne using Grignard reaction 4. Combining the alcohol and alkynyl Grignard reagent 5. Reducing the ester to a tertiary alcohol using lithium aluminum hydride

Step-by-step solution

Selecting the appropriate ketone

Begin with selecting a suitable ketone to use. The target molecule has a tert-butyl group (C(CH3)3) bonded to the oxygen atom, so we should use 2-pentanone as the starting ketone. This will allow for the necessary substitution of the carbon bonded to the oxygen atom: C(=O)CCC

Hydroboration-oxidation of 2-pentanone

Perform hydroboration-oxidation of 2-pentanone with diborane (BH3) followed by treatment with hydrogen peroxide (H2O2) and an aqueous base (e.g. NaOH) solution. This sequence of reactions will convert the ketone functional group to an alcohol: C(=O)CCC \(\xrightarrow[]{\text{BH3, THF}}\) C(OB)CCC \(\xrightarrow[]{\text{H2O2, NaOH}}\) C(OH)CCC

Acetylene to propyne conversion

Convert acetylene (HC≡CH) to propyne (H3C-C≡CH) using a Grignard reaction. First, convert acetylene to ethylmagnesium bromide by treating it with isopropyl bromide (i-BuBr) and magnesium in ether solvent: HC≡CH + \(\text{i-BuMgBr} \xrightarrow[]{\text{Mg, ether}}\text{H3C-C≡CMgBr}\)

Combining the alcohol and alkynyl Grignard reagent

Combine the alkynyl Grignard reagent (propynylmagnesium bromide) with the alcohol obtained from Step 2. The Grignard reagent will react with the hydroxyl group to form the C-C bond and a magnesium bromide salt: C(OH)CCC + \(\text{H3C-C≡CMgBr} \xrightarrow[]{\text{Reflux}}\text{H3C-C≡C-C(O)CCC} + \text{MgBrOH}\)

Reducing the ester to a tertiary alcohol

Finally, reduce the ester formed in the previous step to a tertiary alcohol by treating it with a suitable reducing agent, such as lithium aluminum hydride (LiAlH4) in dry ether solvent followed by an aqueous work-up: H3C-C≡C-C(O)CCC \(\xrightarrow[]{\text{LiAlH4, ether}}\) \(\xrightarrow[]{\text{H2O, reflux}}\) C#CC(C)(O)CC The molecule obtained in Step 5 is the desired final product, Oblivon (meparfynol).