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Questions and Answers
What is the primary oxidation state of palladium involved in common catalytic cycles during homogeneous palladium catalysis?
What is the primary oxidation state of palladium involved in common catalytic cycles during homogeneous palladium catalysis?
Which technique is used to prepare Pd(0) in situ from Pd(II)?
Which technique is used to prepare Pd(0) in situ from Pd(II)?
What role does high-valent palladium play in palladium catalysis?
What role does high-valent palladium play in palladium catalysis?
Which characteristic of Buchwald's precatalysts is significant for palladium catalysis?
Which characteristic of Buchwald's precatalysts is significant for palladium catalysis?
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Why is the formation of an electron-rich Pd(0) species advantageous in cross-coupling reactions?
Why is the formation of an electron-rich Pd(0) species advantageous in cross-coupling reactions?
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What is the primary reason palladium is the preferred catalyst for constructing carbon-carbon bonds?
What is the primary reason palladium is the preferred catalyst for constructing carbon-carbon bonds?
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Which of the following reactions is known to account for over 40% of carbon-carbon bond formations in medicinal chemistry?
Which of the following reactions is known to account for over 40% of carbon-carbon bond formations in medicinal chemistry?
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What are the three major fields of catalysis in organic chemistry?
What are the three major fields of catalysis in organic chemistry?
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What is a notable characteristic of palladium catalysis compared to other metal catalysts?
What is a notable characteristic of palladium catalysis compared to other metal catalysts?
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Which of the following is NOT a reaction associated with palladium catalysis?
Which of the following is NOT a reaction associated with palladium catalysis?
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What advantage does catalyst use provide in the synthesis of organic molecules?
What advantage does catalyst use provide in the synthesis of organic molecules?
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Which of the following statements about palladium catalysis is incorrect?
Which of the following statements about palladium catalysis is incorrect?
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In what context has palladium catalysis gained significant importance in recent years?
In what context has palladium catalysis gained significant importance in recent years?
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Which step in palladium catalysis involves the formation of a palladium complex with the substrate through a reaction that results in an increase in oxidation state?
Which step in palladium catalysis involves the formation of a palladium complex with the substrate through a reaction that results in an increase in oxidation state?
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In the Suzuki-Miyaura reaction, which type of reagent is primarily utilized?
In the Suzuki-Miyaura reaction, which type of reagent is primarily utilized?
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What occurs during the transmetallation step in palladium catalysis?
What occurs during the transmetallation step in palladium catalysis?
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During reductive elimination in palladium catalysis, which of the following best describes the outcome?
During reductive elimination in palladium catalysis, which of the following best describes the outcome?
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Which of the following statements about the Suzuki-Miyaura reaction mechanism is incorrect?
Which of the following statements about the Suzuki-Miyaura reaction mechanism is incorrect?
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What is the purpose of using a base in the Suzuki-Miyaura reaction?
What is the purpose of using a base in the Suzuki-Miyaura reaction?
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Which of these compounds has been noted as a boron reagent utilized in the Suzuki-Miyaura reaction?
Which of these compounds has been noted as a boron reagent utilized in the Suzuki-Miyaura reaction?
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Which reference cited discusses the use of R-Cl in the context of palladium catalysis?
Which reference cited discusses the use of R-Cl in the context of palladium catalysis?
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What is the primary purpose of using bulky electron-rich ligands in palladium catalysis?
What is the primary purpose of using bulky electron-rich ligands in palladium catalysis?
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Which reaction uses carbon monoxide atmosphere for carbonyl insertion into the Pd-C bond?
Which reaction uses carbon monoxide atmosphere for carbonyl insertion into the Pd-C bond?
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What is a distinguishing feature of the Stille Reaction?
What is a distinguishing feature of the Stille Reaction?
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In the context of palladium catalysis, what is the function of transmetallation?
In the context of palladium catalysis, what is the function of transmetallation?
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Which of the following reactions is NOT classified under the palladium-catalyzed cross-coupling reactions?
Which of the following reactions is NOT classified under the palladium-catalyzed cross-coupling reactions?
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What is the significance of less saturated palladium complexes in reactive systems?
What is the significance of less saturated palladium complexes in reactive systems?
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Which palladium-catalyzed reaction is primarily used to synthesize ketone products?
Which palladium-catalyzed reaction is primarily used to synthesize ketone products?
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In palladium catalysis, what is the outcome of oxidative addition?
In palladium catalysis, what is the outcome of oxidative addition?
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What role do terminal alkynes play in the Sonogashira reaction?
What role do terminal alkynes play in the Sonogashira reaction?
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Which of the following statements about the Heck reaction is NOT true?
Which of the following statements about the Heck reaction is NOT true?
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In palladium catalysis, what is the significance of β-hydride elimination being reversible?
In palladium catalysis, what is the significance of β-hydride elimination being reversible?
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Which publication first reported the Sonogashira reaction?
Which publication first reported the Sonogashira reaction?
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What can occur if a Pd(II) intermediate is not syn-coplanar with a β-hydride?
What can occur if a Pd(II) intermediate is not syn-coplanar with a β-hydride?
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What type of catalysis does the Heck reaction employ?
What type of catalysis does the Heck reaction employ?
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In the context of the Heck reaction, what mechanism can lead to the formation of different products?
In the context of the Heck reaction, what mechanism can lead to the formation of different products?
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Which of the following reactions employs a dual catalytic system?
Which of the following reactions employs a dual catalytic system?
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What effect can switching the ligand or nucleophile have in the Tsuji-Trost Reaction?
What effect can switching the ligand or nucleophile have in the Tsuji-Trost Reaction?
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Which transition metals are mentioned as alternatives to palladium for achieving branched products in catalysis?
Which transition metals are mentioned as alternatives to palladium for achieving branched products in catalysis?
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How does the use of chiral ligands in the Tsuji-Trost React to affect stereoselectivity?
How does the use of chiral ligands in the Tsuji-Trost React to affect stereoselectivity?
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What is the primary focus of the literature cited for the Buchwald-Hartwig Reaction?
What is the primary focus of the literature cited for the Buchwald-Hartwig Reaction?
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In which publication year was the notable work on the Tsuji-Trost Reaction published?
In which publication year was the notable work on the Tsuji-Trost Reaction published?
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What is a significant factor that allows asymmetric reactions in palladium catalysis?
What is a significant factor that allows asymmetric reactions in palladium catalysis?
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Which of the following statements best describes the stereoselectivity aspect in the discussed reactions?
Which of the following statements best describes the stereoselectivity aspect in the discussed reactions?
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Which publication primarily addresses the stereoselectivity from predefined stereochemistry?
Which publication primarily addresses the stereoselectivity from predefined stereochemistry?
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Study Notes
Course Information
- Course title: Advanced Synthesis Methods
- Course code: OC4
- Instructor: John J. Molloy
- Semester: Winter 2024/2025
Polar Catalysis
- Palladium Catalysis is a significant area in organic synthesis.
- It's crucial for synthesizing various molecules, including those used in medicinal chemistry, agrochemicals, and materials science.
- Catalysts speed up reactions, making product creation cheaper and faster.
- Three key fields of organic chemistry catalysis include Transition metal, Organocatalysis, and Enzymatic (bio)catalysis.
- Palladium, despite costs and environmental concerns, is often the metal catalyst of choice for C-C or C-heteroatom bond formation due to operational simplicity and high functional group tolerance.
- Palladium catalysts frequently involve two-electron redox cycles, shifting between 0 and +2 oxidation states during catalysis.
Palladium Catalysis - Elementary Steps
- Palladium (0) commonly exists as tetrahedral complexes. They are "electron-rich" and react readily with "electrophilic species."
- Palladium (II) often features square planar complexes, which are "electron-poor" and react with "nucleophilic species."
- Palladium can also attain +3 and +4 oxidation states under harsher oxidizing conditions.
Palladium Catalysis - Reaction Mechanisms
- Ligand dissociation/association: Ligands detach or attach to palladium.
- Oxidative addition: A substrate and other species join with Pd creating bonds between the species and the Pd.
- Transmetallation: Transfer of an organic group to the Pd compound.
- Reductive elimination: The Pd intermediate releases two groups.
- β-Hydride Elimination: A hydrogen group breaks off from the Pd intermediate, which produces an alkene.
- Migratory insertion: A bond is formed between two organic groups leading to a Pd intermediate.
Generating Pd(0) from Pd(II)
- Pre-formed Pd(0) (like Pd(PPh3)4) is costly, sensitive, and excess PPh3 can inhibit reactions.
- Pd2(dba)3 is a more air-stable alternative precursor, also expensive, but readily converted to Pd(PPh3)2.
- In situ preparation of Pd(0) from Pd(II), using reagents like PdCl2 is often preferable (cheaper and less sensitive).
Specific Palladium-Catalyzed Reactions
- Suzuki-Miyaura Reaction: Coupling of aryl or vinyl halides with aryl or vinyl boronic acids.
- Stille Reaction: Coupling of aryl or vinyl halides with alkyl or aryl tin compounds.
- Hiyama Reaction: Coupling of aryl or vinyl halides with silyl compounds.
- Kumada Coupling: Coupling of aryl or vinyl halides with Grignard reagents.
- Negishi Reaction: Coupling of aryl or vinyl halides with organozinc compounds.
- Sonogashira Reaction: Coupling of aryl or vinyl halides with terminal alkynes.
- Heck Reaction: Coupling of aryl halides or vinyl halides with alkenes or alkynes. Typically forms the E alkene isomer.
- Buchwald-Hartwig Amination: Coupling of aryl or alkyl halides with amines.
- Tsuji-Trost Reaction: Allylic substitution with palladium catalysis.
Important Aspects of Pd Catalysis
- Importance of catalysis in organic synthesis, covering medicinal chemistry, agrochemicals, and materials science.
- Importance of the choice of ligands (e.g. diphosphines to prevent ligation).
- Reaction conditions for certain transformations are vital. For instance, the Heck reaction requires a base.
- Regioselectivity (and stereoselectivity) heavily depend upon the catalyst system and the substrates.
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Description
Test your knowledge on palladium catalysis with this comprehensive quiz. Explore essential concepts such as oxidation states, catalytic cycles, and the unique properties of palladium in carbon-carbon bond formations. Perfect for students and professionals in organic chemistry.
