Question

11. (10 pts) Suggest an efficient reaction sequence for the preparation of the following compound from the indicated starting materials and any other necessary reagents. o from from = and and (use twice) use twice)

Answer 1

References:

* NBS is N-Bromosuccinimide. This reagent follows radical mechanism and carries out bromination at allylic and benzylic positions using a peroxide as initiator.

* Terminal alkynes are slightly acidic due to high electronegativity of sp-hybridized carbon and hence reacts with sodium metal to generate the desired nucleophile(acid-base reaction).

* Reaction of acetylide with 2 equivalents of Benzyl bromide is an example of nucleophilic substitution(SN2).

* Mild catalytic reduction does not reduce benzene ring, for that reaction with hydrogen and nickel catalyst has to be carried out at high temperature.

* Alcoholic KOH removes a molecule of HX from haloalkane to give a >C=C< bond.

ANSWER: NBS CH₂ Br peroxide . CH2> SN2 (2 Equivalents) (2 Equivalents) CH CH=CH +2 Na - NaC ECNa acetylide ion (Nucleophile) H₂, Pd Catalytic Hydrogenation CH2 BY NBS () Eq) CH₂ CH2 CH. peroxide Alcoholic kon B-Elimination CH₂ CH2 CH=CH CH₂ alent to