Podcast
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?
- +2 (correct)
- +1
- 0
- +3
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)?
- Reductive elimination (correct)
- Oxidative addition
- Thermal decomposition
- Photochemical reduction
What role does high-valent palladium play in palladium catalysis?
What role does high-valent palladium play in palladium catalysis?
- It is the active form for cross-coupling reaction.
- It participates in the formation of Pd(0).
- It facilitates the initial oxidation of reagents.
- It is involved in two-electron redox cycles. (correct)
Which characteristic of Buchwald's precatalysts is significant for palladium catalysis?
Which characteristic of Buchwald's precatalysts is significant for palladium catalysis?
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?
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?
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?
What are the three major fields of catalysis in organic chemistry?
What are the three major fields of catalysis in organic chemistry?
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?
Which of the following is NOT a reaction associated with palladium catalysis?
Which of the following is NOT a reaction associated with palladium catalysis?
What advantage does catalyst use provide in the synthesis of organic molecules?
What advantage does catalyst use provide in the synthesis of organic molecules?
Which of the following statements about palladium catalysis is incorrect?
Which of the following statements about palladium catalysis is incorrect?
In what context has palladium catalysis gained significant importance in recent years?
In what context has palladium catalysis gained significant importance in recent years?
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?
In the Suzuki-Miyaura reaction, which type of reagent is primarily utilized?
In the Suzuki-Miyaura reaction, which type of reagent is primarily utilized?
What occurs during the transmetallation step in palladium catalysis?
What occurs during the transmetallation step in palladium catalysis?
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?
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?
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?
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?
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?
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?
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?
What is a distinguishing feature of the Stille Reaction?
What is a distinguishing feature of the Stille Reaction?
In the context of palladium catalysis, what is the function of transmetallation?
In the context of palladium catalysis, what is the function of transmetallation?
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?
What is the significance of less saturated palladium complexes in reactive systems?
What is the significance of less saturated palladium complexes in reactive systems?
Which palladium-catalyzed reaction is primarily used to synthesize ketone products?
Which palladium-catalyzed reaction is primarily used to synthesize ketone products?
In palladium catalysis, what is the outcome of oxidative addition?
In palladium catalysis, what is the outcome of oxidative addition?
What role do terminal alkynes play in the Sonogashira reaction?
What role do terminal alkynes play in the Sonogashira reaction?
Which of the following statements about the Heck reaction is NOT true?
Which of the following statements about the Heck reaction is NOT true?
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?
Which publication first reported the Sonogashira reaction?
Which publication first reported the Sonogashira reaction?
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?
What type of catalysis does the Heck reaction employ?
What type of catalysis does the Heck reaction employ?
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?
Which of the following reactions employs a dual catalytic system?
Which of the following reactions employs a dual catalytic system?
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?
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?
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?
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?
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?
What is a significant factor that allows asymmetric reactions in palladium catalysis?
What is a significant factor that allows asymmetric reactions in palladium catalysis?
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?
Which publication primarily addresses the stereoselectivity from predefined stereochemistry?
Which publication primarily addresses the stereoselectivity from predefined stereochemistry?
Flashcards
Palladium Catalysis
Palladium Catalysis
A crucial method in organic synthesis, employing palladium as a catalyst to form carbon-carbon or carbon-heteroatom bonds.
Suzuki-Miyaura Reaction
Suzuki-Miyaura Reaction
A specific type of palladium-catalyzed coupling reaction, frequently used to create carbon-carbon bonds.
Transition Metal Catalysis
Transition Metal Catalysis
A major field of catalysis in organic chemistry, involving metals like palladium in bond formation reactions.
Organocatalysis
Organocatalysis
A catalysis method in organic chemistry, not involving metals but using organic molecules as catalysts.
Signup and view all the flashcards
High Functional Group Tolerance
High Functional Group Tolerance
A characteristic of palladium catalysis, enabling diverse types of molecules to participate in the reactions without interfering.
Signup and view all the flashcards
Catalysis in Organic Chemistry
Catalysis in Organic Chemistry
Methods that speed up chemical reactions, essential for efficient and cost-effective synthesis of molecules.
Signup and view all the flashcards
Nobel Prize in Chemistry
Nobel Prize in Chemistry
An award recognizing exceptional contributions to chemistry.
Signup and view all the flashcards
C-C Bond Formation
C-C Bond Formation
Creation of bonds between carbon atoms.
Signup and view all the flashcards
Pd(0)
Pd(0)
Active catalyst in cross-coupling reactions.
Signup and view all the flashcards
Generating Pd(0) from Pd(II)
Generating Pd(0) from Pd(II)
Preparing Pd(0) catalyst from Pd(II) in situ for cross-coupling reactions.
Signup and view all the flashcards
Buchwald precatalysts
Buchwald precatalysts
A set of catalysts developed to quickly form Pd(0). (Now commercial).
Signup and view all the flashcards
Reductive elimination
Reductive elimination
Mechanism for forming Pd(0) from Pd(II).
Signup and view all the flashcards
Oxidative Addition
Oxidative Addition
A crucial step in palladium catalysis where a palladium atom bonds with two different atoms or groups in a molecule
Signup and view all the flashcards
Transmetallation
Transmetallation
A chemical reaction where a metal in a complex is replaced by another metal
Signup and view all the flashcards
Suzuki-Miyaura Mechanism
Suzuki-Miyaura Mechanism
Reaction steps involving palladium, boron-containing compounds and base.
Signup and view all the flashcards
Boron Reagents in Suzuki-Miyaura
Boron Reagents in Suzuki-Miyaura
Boron-containing molecules are used to link with different molecules. The boron compounds are often esters or acids.
Signup and view all the flashcards
Iterative Synthesis
Iterative Synthesis
A process where one reaction step is repeated in a series to create progressively more complex molecules.
Signup and view all the flashcards
Bulky Phosphine Ligands
Bulky Phosphine Ligands
These ligands are used in palladium catalysis to enhance the reactivity of the palladium complex, particularly with sterically hindered substrates.
Signup and view all the flashcards
Stille Reaction
Stille Reaction
A palladium-catalyzed cross-coupling reaction that joins an organotin compound with an organic halide. It's widely used in organic synthesis, particularly for forming carbon-carbon bonds.
Signup and view all the flashcards
Hiyama Reaction
Hiyama Reaction
A palladium-catalyzed coupling reaction involving an organosilicon compound and an organic halide. This reaction is known for its high functional group tolerance.
Signup and view all the flashcards
Kumada Reaction
Kumada Reaction
A palladium-catalyzed coupling reaction joining an organomagnesium compound with an organic halide, primarily used for carbon-carbon bond formation.
Signup and view all the flashcards
Negishi Reaction
Negishi Reaction
A palladium-catalyzed cross-coupling reaction involving an organozinc compound and an organic halide. It's effective for forming carbon-carbon bonds and is known for its broad substrate scope.
Signup and view all the flashcards
Carbonylation
Carbonylation
A process in palladium catalysis where carbon monoxide is introduced into the reaction, resulting in the formation of carbonyl groups in the final product.
Signup and view all the flashcards
What is the role of bulky electron-rich ligands?
What is the role of bulky electron-rich ligands?
Bulky electron-rich ligands increase the reactivity of palladium complexes, making them more effective in promoting oxidative addition reactions, especially with sterically hindered aryl halides. This allows for efficient coupling reactions with these challenging substrates
Signup and view all the flashcards
Why are less saturated palladium complexes useful?
Why are less saturated palladium complexes useful?
These complexes are more reactive in oxidative addition, which is a key step in palladium-catalyzed coupling reactions. Their ability to accommodate a wider variety of substrates makes them particularly useful for coupling reactions involving sterically hindered aryl halides.
Signup and view all the flashcards
Sonogashira Reaction
Sonogashira Reaction
A palladium-catalyzed coupling reaction where a terminal alkyne reacts with an aryl or vinyl halide. The reaction requires copper to generate a copper acetylide, acting as the catalyst.
Signup and view all the flashcards
Heck Reaction
Heck Reaction
A palladium-catalyzed coupling reaction involving an alkene and an aryl or vinyl halide. Forms a new carbon-carbon bond by adding the aryl or vinyl group to the alkene.
Signup and view all the flashcards
Neutral vs. Cationic Heck
Neutral vs. Cationic Heck
Different forms of the Heck reaction, distinguished by the palladium catalyst's oxidation state. Neutral Heck uses Pd(0) and cationic Heck uses Pd(II).
Signup and view all the flashcards
Syn-Coplanarity
Syn-Coplanarity
A specific spatial arrangement required for β-hydride elimination in the Heck reaction. The carbon-palladium bond and the β-hydrogen must be on the same plane, with a dihedral angle of 0°.
Signup and view all the flashcards
Cascade Processes
Cascade Processes
Alternative reaction pathways in the Heck reaction when syn-coplanarity for β-hydride elimination isn't possible. Involves a series of steps leading to product formation.
Signup and view all the flashcards
Alkene Walking
Alkene Walking
A reversible process in the Heck reaction where the double bond of the product can shift to a different position. Also known as positional isomerization.
Signup and view all the flashcards
β-Hydride Elimination
β-Hydride Elimination
A key step in the Heck mechanism. Palladium removes a hydrogen atom from a carbon atom adjacent to the palladium-carbon bond, forming a new double bond.
Signup and view all the flashcards
Buchwald-Hartwig Reaction
Buchwald-Hartwig Reaction
A palladium-catalyzed reaction forming carbon-nitrogen bonds between an aryl or vinyl halide and an amine. It's a powerful tool in organic synthesis, particularly for creating pharmaceuticals.
Signup and view all the flashcards
Tsuji-Trost Reaction
Tsuji-Trost Reaction
A palladium-catalyzed reaction where an allyl compound is reacted with a nucleophile to form a new carbon-carbon bond. It's highly versatile and used in synthesis for various organic transformations.
Signup and view all the flashcards
Regioselectivity in Tsuji-Trost
Regioselectivity in Tsuji-Trost
The ability to control where the new carbon-carbon bond forms in a Tsuji-Trost reaction, favoring either a linear or branched outcome.
Signup and view all the flashcards
Stereoselectivity from Predefined Stereochemistry
Stereoselectivity from Predefined Stereochemistry
Using starting molecules with existing stereochemistry (chirality) to control the stereochemistry of the newly formed product in Tsuji-Trost reactions.
Signup and view all the flashcards
Stereoselectivity with Chiral Ligands
Stereoselectivity with Chiral Ligands
Controlling the stereochemistry of the product by attaching a chiral ligand (molecule) to the palladium catalyst in Tsuji-Trost reactions.
Signup and view all the flashcards
Pd Catalyst in Tsuji-Trost
Pd Catalyst in Tsuji-Trost
Palladium acts as a catalyst in Tsuji-Trost reactions, speeding up bond formations and promoting reaction efficiency.
Signup and view all the flashcards
Ligands in Asymmetric Tsuji-Trost Reactions
Ligands in Asymmetric Tsuji-Trost Reactions
Chiral ligands attached to the palladium catalyst are crucial for controlling stereoselectivity in asymmetric Tsuji-Trost reactions, leading to the formation of a specific enantiomer of the product.
Signup and view all the flashcardsStudy 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.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.