Question

Using your reaction roadmap as a guide, show how to convert cyclohexanol into racemic trans-1,2-cyclohexanediol. Show all required reagents and all molecules synthesized along the way.

Short answer

Answer: The conversion of cyclohexanol into racemic trans-1,2-cyclohexanediol involves three main steps: 1. Oxidation of cyclohexanol to cyclohexanone using pyridinium chlorochromate (PCC) in dichloromethane (DCM). 2. Formation of racemic epoxide mixture using lithium diisopropylamide (LDA) and methyl chloroformate as reagents. 3. Hydrolysis of the epoxide product using aqueous sodium hydroxide (NaOH) to obtain the target product, racemic trans-1,2-cyclohexanediol.

Step-by-step solution

Conversion of Cyclohexanol to Cyclohexanone

To convert cyclohexanol to cyclohexanone, we need an oxidation reaction. We can use a mild oxidizing agent to accomplish this. A suitable reagent is pyridinium chlorochromate (PCC) in dichloromethane (DCM). The reaction is shown as follows: Cyclohexanol + PCC/DCM → Cyclohexanone

Formation of Racemic Mixture of Epoxides

To convert cyclohexanone to the epoxide form, we can use a base like lithium diisopropylamide (LDA) to form an enolate and then react with a halogenating agent such as methyl chloroformate. The resulting mixture will be racemic, containing both enantiomers of the epoxide product. The reaction is represented as: Cyclohexanone + LDA → Enolate intermediate Enolate intermediate + Methyl chloroformate → (±)-methyl 2-chloro-2-cyclohexyloxirane carboxylate

Hydrolysis of the Epoxide

In this step, we will hydrolyze the (±)-methyl 2-chloro-2-cyclohexyloxirane carboxylate to obtain racemic trans-1,2-cyclohexanediol. To achieve this, we will use an aqueous base like sodium hydroxide (NaOH) in water. The reaction is shown as follows: (±)-methyl 2-chloro-2-cyclohexyloxirane carboxylate + NaOH → (±)-trans-1,2-cyclohexanediol + NaCl + CO2 Thus, to convert cyclohexanol into racemic trans-1,2-cyclohexanediol, we have to perform the following steps: 1. Oxidation of cyclohexanol to cyclohexanone using PCC/DCM. 2. Formation of racemic epoxide mixture using LDA and methyl chloroformate as reagents. 3. Hydrolysis of the epoxide product using aqueous NaOH to obtain the target product, racemic trans-1,2-cyclohexanediol.