Question

Show how you would accomplish the following transformations. Some of these examples require more than one step.

Short answer

(a)

(b)

(c)

(d)

(e)

Step-by-step solution

Synthesis of epoxides

Epoxides can be easily made from alkenes and they undergo a number of useful synthetic reactions. Epoxides are known as valuable synthetic intermediates.

Peroxyacid epoxidation

Peroxyacids can be used to convert alkenes to epoxides. The epoxides are known to open to a glycol if the reaction occur in an aqueous medium. For this reason, strong acids are avoided for the synthesis of epoxides. meta-chloroperoxybenzoic acid (mCPBA) can be used for epoxidations process because of its desirable soluble properties. mCPBA is weakly acidic peroxy acid and is soluble in aprotic solvent like CH₂Cl₂. The reaction proceeds in a one-step concerted manner where the stereochemistry of any substituents around the double bond is maintained.

Synthesis

(a) 2-methylpropene reacts with meta-chloroperoxybenzoic acid (mCPBA) in a one-step concerted process to give 2,2-dimethyloxuirane.

(b) 1-phenylethanol on treatment with H₂SO₄ forms styrene, which on further treatment with meta-chloroperoxybenzoic acid (mCPBA) gives 2-phenyloxirane .

(c) 5-chloropent-1-ene on treatment with BH₃, THF/H₂O₂, OH^- forms 5-chloropent-1-ol which loses a hydroxide ion to give tetrahydropyran

(d) 5-chloropent-1-ene on treatment with Hg(OAc)₂, H₂O/NaBH₄ forms 5-chloropent-2-ol which loses a hydroxide ion to give 2-methyltetrahydrofuran.

(e) 2-chlorohexan-1-ol loses a hydroxide ion to give 1,2-epoxyhexane.