Question

Synthesize the compounds shown below utilizing only the carbon sources provided and any reagents of your choosing.

Target Molecules Carbon Sources H3C OH OH 了」 。 Hsc

Answer 1

Propionic acid can be utilized to prepare intermediates like propyl bromide, propylmagnesium bromide and propyltriphenylphosphonium bromide.

Preparation of propyl bromide intermediate:

ОН Т" . Ан , луч сиво ,лов OH PBr3 1. LiAlH4 2. Н307

Step 1: Propionic acid is reduced to propyl alcohol using lithium aluminum hydride.

Step 2: Propyl alcohol is converted to propyl bromide using phosphorous tribromide.

Preparation of propylmagnesium bromide intermediate:

Br Mg MgBr

Step 3: Propyl bromide is converted to propyl magnesium bromide using magnesium metal.

Preparation of propyltriphenylphosphonium bromide intermediate:

PPh3 PPh3 Bro

Step 4: Propyl bromide is converted to propyltriphenylphosphonium bromide using triphenylphosphine.

Synthesis of target molecules:

LDA MgBr 1. 1 eqv. PCC -OH = 0 2. Hj0 PPh; Bre n-BuLi CH3

Step 5: Cyclopentyl alcohol is converted to cyclopentanone using PCC (pyridinium chlorochromate).

Step 6: LDA (lithium diisopropylamide) abstracts alpha proton of cyclopentanone. The carbanion thus formed then react with propyl bromide from step 2 to give alpha propyl substituted cyclopentanone.

Step 7: The product formed in step 6 is converted to the target molecule containing tertiary alcohol using propyl magnesium bromide which is prepared in step 3.

Step 8: Cyclopentanone can be converted to the other target molecule using Wittig reaction with propyltriphenylphosphonium bromide which is prepared is step 4.