Textbook Question
Show how the following products might be synthesized from suitable Michael donors and acceptors.
(f)
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Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
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Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 57
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 57Chapter 22, Problem 57
Propose a mechanism for the following reaction.
Verified step by step guidance1
Step 1: Analyze the reactants and products. The reaction involves two ketones: 1-tetralone and methyl vinyl ketone, reacting in the presence of hydroxide (HO⁻). The product is a fused bicyclic compound with a new C-C bond formed between the two reactants. This suggests a Michael addition followed by aldol condensation.
Step 2: Initiate the reaction mechanism with the enolate formation. The hydroxide ion deprotonates the alpha-carbon of 1-tetralone, forming an enolate ion. The enolate is stabilized by resonance between the alpha-carbon and the carbonyl group.
Step 3: Perform the Michael addition. The enolate ion attacks the beta-carbon of methyl vinyl ketone (a conjugated ketone), forming a new C-C bond. This step results in the formation of a new intermediate with the two reactants connected.
Step 4: Proceed with aldol condensation. The intermediate formed undergoes intramolecular aldol condensation. The hydroxide ion deprotonates the alpha-carbon adjacent to the newly formed ketone, generating another enolate. This enolate attacks the carbonyl group within the same molecule, forming a cyclic structure.
Step 5: Complete the reaction with dehydration. The aldol product undergoes elimination of water (dehydration) to form the final conjugated bicyclic product. This step is facilitated by the basic conditions provided by hydroxide.
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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 a series of reactions, typically involving a Michael addition followed by an intramolecular aldol condensation. This mechanism is crucial for synthesizing complex cyclic structures and is widely used in the synthesis of steroids and other natural products.
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Robinson Annulation
Michael Addition
The Michael addition is a nucleophilic addition reaction where a nucleophile adds to an α,β-unsaturated carbonyl compound. This step is essential in the Robinson Annulation mechanism, as it forms a new carbon-carbon bond, setting the stage for subsequent reactions that lead to ring formation and product synthesis.
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Aldol Condensation
Aldol condensation is a reaction between aldehydes or ketones that results in 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 critical for closing the ring and stabilizing the final product through the formation of double bonds.
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Related Practice
Textbook Question
Show how the following products might be synthesized from suitable Michael donors and acceptors.
(e)
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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)
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.)
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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.
(b)
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Textbook Question
Show how the following products might be synthesized from suitable Michael donors and acceptors.
(d)
2
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