Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

25. Condensation Chemistry

Robinson Annulation

Organic Chemistry

25. Condensation Chemistry

Robinson Annulation

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4:10 minutes

Problem 67a

Textbook Question

Show how you would use the Robinson annulation to synthesize the following compounds.
(a)

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Step 1: Identify the target molecule as a bicyclic compound containing a cyclohexenone ring fused to a phenyl-substituted ring. This suggests the use of the Robinson annulation, which combines a Michael addition followed by an intramolecular aldol condensation.

Step 2: Determine the precursor molecules for the Robinson annulation. The cyclohexenone ring indicates that a β-keto ester or diketone will be used as the nucleophile, while the phenyl-substituted ring suggests a conjugated enone as the electrophile.

Step 3: Select the appropriate enone and nucleophile. For this synthesis, the enone could be phenyl vinyl ketone (Ph-CH=CH-COCH3), and the nucleophile could be a methyl ketone such as 2-ethyl-1,3-cyclohexanedione.

Step 4: Perform the Michael addition. The nucleophile (2-ethyl-1,3-cyclohexanedione) attacks the conjugated double bond of phenyl vinyl ketone, forming a new carbon-carbon bond and generating an intermediate with a β-diketone structure.

Step 5: Carry out the intramolecular aldol condensation. The intermediate undergoes cyclization, forming the six-membered ring and completing the Robinson annulation to yield the target bicyclic compound.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Robinson Annulation

The Robinson annulation is a key synthetic method in organic chemistry that combines a Michael addition and an intramolecular aldol condensation. This reaction typically involves a cyclic ketone and an α,β-unsaturated carbonyl compound, leading to the formation of a six-membered ring. It is particularly useful for constructing complex cyclic structures, making it a valuable tool in the synthesis of natural products and pharmaceuticals.

Michael Addition

The Michael addition is a nucleophilic addition reaction where a nucleophile adds to an α,β-unsaturated carbonyl compound. This reaction is crucial in the Robinson annulation as it forms the initial bond between the nucleophile and the electrophile, setting the stage for subsequent reactions. Understanding the reactivity of the nucleophile and the electrophile is essential for predicting the outcome of the reaction.

Aldol Condensation

Aldol condensation is a reaction between aldehydes or ketones that contain α-hydrogens, leading to the formation of β-hydroxy carbonyl compounds. In the context of the Robinson annulation, this step occurs after the Michael addition, where the newly formed compound undergoes dehydration to yield an enone. This transformation is critical for creating the final cyclic structure and understanding the reaction mechanism.

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Show how you would use the Robinson annulation to synthesize the following compounds.(a)

Key Concepts

Robinson Annulation

Michael Addition

Aldol Condensation

Watch next

Show how you would use the Robinson annulation to synthesize the following compounds.
(a)