Aldehydes & Ketones: Multi-Step Synthesis
Suggest a synthetic scheme for the conversion shown on the left using the starting material indicated. Work each problem backwards, and draw the structures of the intermediate required for the conversion, and the reaction conditions necessary for each step.Click the mouse on the buttons to view the synthetic logic, the structure of the intermediate and the solution to the problem.
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Working backwards, a phenyl group and an isopropylidene substituent have been added to the carbon skeleton of the starting material. Since the starting material is an a-b-unsaturated ketone, the phenyl group could be introduced at the b-position using a diarylcopper lithium reagent; the carbonyl could then be converted to the exocyclic alkene using a Wittig reaction. First, draw the structure of the intermediate required for the Wittig reaction, and the structure of the required Wittig reagent.
A phenyl group and an isopropylidene substituent have been added to the carbon skeleton of the starting material. Since the starting material is an a-b-unsaturated ketone, the phenyl group could be introduced at the b-position using a diarylcopper lithium reagent; the carbonyl could then be converted to the exocyclic alkene using a Wittig reaction, as shown above. Next, suggest a synthesis of this ketone, beginning with 2-cyclohexenone.
2-Cyclohexenone is reacted with diphenylcopper lithium reagent to give 3-phenylcyclohexanone. The carbonyl is then be converted to the exocyclic alkene using a Wittig reaction.