Fundamentals of Organic ChemistryChemistryAlcohols Phenols and Ethers
Which of the following reagent sequences is most appropriate for the given transformation?
Options
- A(i) BH ₃ (ii) H ₂ O ₂ / NaOH
- B(i) H ₂ O (ii) NaOH
- CHBr / peroxides
- D(i) aq. H ₂ SO ₄ (ii) Na (iii) NaI / acetone
Correct answer
A. (i) BH ₃ (ii) H ₂ O ₂ / NaOH
Step-by-step solution
The transformation requires the conversion of 5 -chloro- 1 -pentene to tetrahydropyran, a 6 -membered cyclic ether. To form this 6 -membered ring, an oxygen atom must be introduced at the terminal carbon of the alkene, which can then undergo an intramolecular nucleophilic substitution to displace the chlorine atom. Hydroboration-oxidation using (i) BH ₃ and (ii) H ₂ O ₂ / NaOH results in the anti-Markovnikov addition of water across the double bond, yielding 5 -chloro- 1 -pentanol: Cl-(CH₂)₃-CH=CH₂ BH ₃, then H ₂ O