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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8:51 minutes

Problem 44

Textbook Question

Show how the following molecule might be synthesized using the Robinson annulation.

Verified step by step guidance

Identify the target molecule as a bicyclic compound with a ketone and an alpha-beta unsaturated system, which is a typical product of a Robinson annulation.

Recognize that Robinson annulation involves a Michael addition followed by an intramolecular aldol condensation. The starting materials are typically a ketone and an alpha, beta-unsaturated carbonyl compound.

Select a suitable alpha, beta-unsaturated carbonyl compound, such as methyl vinyl ketone, which will participate in the Michael addition.

Choose a suitable ketone that can form the enolate ion needed for the Michael addition. In this case, cyclohexanone can be used as it can form an enolate that will add to the methyl vinyl ketone.

Perform the Robinson annulation: First, generate the enolate from cyclohexanone using a base. Then, carry out the Michael addition with methyl vinyl ketone. Finally, perform an intramolecular aldol condensation to form the second ring and complete the synthesis of the target molecule.

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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 reaction in organic chemistry that involves the formation of a six-membered ring through the condensation of a ketone with a cyclic enone. This reaction typically consists of two main steps: an initial Michael addition followed by an intramolecular aldol condensation. Understanding this process is crucial for synthesizing complex molecules, as it allows for the construction of cyclic structures that are prevalent in natural products.

Michael Addition

Michael addition is a fundamental reaction in organic chemistry where a nucleophile adds to an α,β-unsaturated carbonyl compound. This step is essential in the Robinson annulation, as it forms a new carbon-carbon bond, setting the stage for the subsequent cyclization. Recognizing the role of nucleophiles and electrophiles in this reaction helps in predicting the outcome of the synthesis.

Aldol Condensation

Aldol condensation is a reaction between aldehydes or ketones that leads to the formation of β-hydroxy carbonyl compounds, which can further dehydrate to form α,β-unsaturated carbonyl compounds. In the context of the Robinson annulation, this step is crucial for closing the ring and completing the synthesis of the desired cyclic structure. Understanding the conditions that favor aldol condensation, such as the presence of a base, is vital for successful synthesis.

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Related Practice

Textbook Question

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

(b)

Textbook Question

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

(c)

Textbook Question

Predict the product of the following reactions.

(a)

Textbook Question

Predict the product of the following reactions.

(b)

Textbook Question

Propose mechanisms for the following reactions.

(d)

Textbook Question

The base-catalyzed reaction of an aldehyde (having no α hydrogens) with an anhydride is called the Perkin condensation. Propose a mechanism for the following example of the Perkin condensation. (Sodium acetate serves as the base.)

Textbook Question

Show how you would use Robinson annulations to synthesize the following compounds. Work backward, remembering that the cyclohexenone is the new ring and that the double bond of the cyclohexenone is formed by the aldol with dehydration. Take apart the double bond, then see what structures the Michael donor and acceptor must have.

(a)

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