The document discusses various organic synthesis reactions involving organometallic compounds, including:
1) Enantioselective functional group interconversions and carbon-carbon bond formation reactions like the Tsuji-Trost reaction and carbonyl/alkene insertions.
2) Carbon-carbon bond formation through cross-coupling reactions like Stille, Suzuki, Sonogashira, and Negishi couplings and through cyclization reactions.
3) Asymmetric catalysis for enantioselective hydrogenation of carbon-carbon double and carbonyl bonds using rhodium, ruthenium, and iridium catalysts.
This document provides an overview of organometallic chemistry. It discusses various organometallic reagents including Grignard reagents, organolithium reagents, organocuprate reagents, and their reactions. It also summarizes important organometallic reactions such as the Suzuki coupling and ring closing metathesis. Organometallic chemistry allows the formation of carbon-carbon bonds that were previously difficult to form using classical organic synthesis.
This document discusses asymmetric synthesis, which produces unequal amounts of stereoisomers from achiral precursors. It can be enantioselective or diastereoselective. There are two types: partial asymmetric synthesis, which forms a new chiral center from an achiral precursor using a chiral substrate, auxiliary, reagent, or catalyst; and absolute asymmetric synthesis, which uses no chiral precursors but instead relies on physical chirality like circularly polarized light. Common approaches include using a chiral pool substrate, chiral auxiliary, chiral reagent, or chiral catalyst. The mechanisms and examples of various methods are explained in detail.
Gilman reagent, also known as organocopper reagents, are prepared by reacting organomagnesium, organolithium, or organozinc reagents with copper(I) salts. Gilman reagents react with a variety of electrophiles including acid chlorides, aldehydes, ketones, epoxides, and alkyl halides. Some common reactions of Gilman reagents are: 1) reactions with acid chlorides to form ketones, 2) coupling reactions between two different alkyl halides to form C-C bonds, and 3) conjugate addition reactions of the organocopper reagent to unsaturated carbonyl compounds like enones. Gilman reagents offer advantages over Grignard reagents for
This document discusses various aspects of asymmetric synthesis, including stereochemical aspects, acyclic and cyclic stereoselection, and enantioselective synthesis. It defines terms like racemate, enantiopure, and enantiomer. It describes stereospecific and stereoselective reactions, and rules like Cram's rule and Prelog's rule that help explain stereoselection. It discusses strategies for stereoselective synthesis including additions to carbonyls and aldol reactions. It also covers topics like diastereoselective oxidations, catalytic hydrogenation, and enantioselective reductions using chiral reagents like (S)-PBMgCl and (R,R)-DIOP.
The document discusses retrosynthetic analysis, which is a problem-solving technique used in organic synthesis. It involves working backwards from the target molecule and breaking it down into simpler structures through the reverse of known reactions. This allows chemists to plan a synthesis by tracing the target back to commercially available starting materials. The document outlines common disconnections, reactions, and strategies used in retrosynthetic analysis and organic synthesis planning.
1) Alkenes are hydrocarbons containing a carbon-carbon double bond. They include many naturally occurring compounds like flavors and fragrances.
2) This chapter focuses on the general reaction of alkenes, which is electrophilic addition. It examines the consequences of alkene stereoisomerism and how double bonds are present in most organic molecules.
3) Electrophilic addition of alkenes involves the attack of an electrophile like HBr on the pi bond, forming a carbocation intermediate that then reacts with the bromide ion. This two-step process allows preparations using HCl or HI as well.
This document discusses various types of organometallic compounds. It defines organometallic chemistry as the study of compounds with a carbon-metal bond. Key types discussed include organolithium, organomagnesium (Grignard reagents), organozinc, and organocopper compounds. The document also summarizes several important reactions of these compounds, such as addition reactions, cross-coupling reactions, and cyclopropanation.
This document provides an overview of organometallic chemistry. It discusses various organometallic reagents including Grignard reagents, organolithium reagents, organocuprate reagents, and their reactions. It also summarizes important organometallic reactions such as the Suzuki coupling and ring closing metathesis. Organometallic chemistry allows the formation of carbon-carbon bonds that were previously difficult to form using classical organic synthesis.
This document discusses asymmetric synthesis, which produces unequal amounts of stereoisomers from achiral precursors. It can be enantioselective or diastereoselective. There are two types: partial asymmetric synthesis, which forms a new chiral center from an achiral precursor using a chiral substrate, auxiliary, reagent, or catalyst; and absolute asymmetric synthesis, which uses no chiral precursors but instead relies on physical chirality like circularly polarized light. Common approaches include using a chiral pool substrate, chiral auxiliary, chiral reagent, or chiral catalyst. The mechanisms and examples of various methods are explained in detail.
Gilman reagent, also known as organocopper reagents, are prepared by reacting organomagnesium, organolithium, or organozinc reagents with copper(I) salts. Gilman reagents react with a variety of electrophiles including acid chlorides, aldehydes, ketones, epoxides, and alkyl halides. Some common reactions of Gilman reagents are: 1) reactions with acid chlorides to form ketones, 2) coupling reactions between two different alkyl halides to form C-C bonds, and 3) conjugate addition reactions of the organocopper reagent to unsaturated carbonyl compounds like enones. Gilman reagents offer advantages over Grignard reagents for
This document discusses various aspects of asymmetric synthesis, including stereochemical aspects, acyclic and cyclic stereoselection, and enantioselective synthesis. It defines terms like racemate, enantiopure, and enantiomer. It describes stereospecific and stereoselective reactions, and rules like Cram's rule and Prelog's rule that help explain stereoselection. It discusses strategies for stereoselective synthesis including additions to carbonyls and aldol reactions. It also covers topics like diastereoselective oxidations, catalytic hydrogenation, and enantioselective reductions using chiral reagents like (S)-PBMgCl and (R,R)-DIOP.
The document discusses retrosynthetic analysis, which is a problem-solving technique used in organic synthesis. It involves working backwards from the target molecule and breaking it down into simpler structures through the reverse of known reactions. This allows chemists to plan a synthesis by tracing the target back to commercially available starting materials. The document outlines common disconnections, reactions, and strategies used in retrosynthetic analysis and organic synthesis planning.
1) Alkenes are hydrocarbons containing a carbon-carbon double bond. They include many naturally occurring compounds like flavors and fragrances.
2) This chapter focuses on the general reaction of alkenes, which is electrophilic addition. It examines the consequences of alkene stereoisomerism and how double bonds are present in most organic molecules.
3) Electrophilic addition of alkenes involves the attack of an electrophile like HBr on the pi bond, forming a carbocation intermediate that then reacts with the bromide ion. This two-step process allows preparations using HCl or HI as well.
This document discusses various types of organometallic compounds. It defines organometallic chemistry as the study of compounds with a carbon-metal bond. Key types discussed include organolithium, organomagnesium (Grignard reagents), organozinc, and organocopper compounds. The document also summarizes several important reactions of these compounds, such as addition reactions, cross-coupling reactions, and cyclopropanation.
The document defines and provides examples of various sigmatropic reactions, including:
1. The Claisen rearrangement, which involves the [3,3] rearrangement of an allyl vinyl ether.
2. The Cope rearrangement, which involves the [3,3] sigmatropic rearrangement of 1,5-dienes.
3. The Oxy-Cope rearrangement, which has a hydroxyl substituent and proceeds faster when deprotonated.
4. Other reactions discussed include the Fischer indole synthesis, aromatic Claisen rearrangement, [2,3]-Wittig rearrangement, Carroll rearrangement, and walk rearrangements. Mechanisms
This document discusses metathesis reactions and their applications in organic synthesis. It begins with definitions and examples of different types of metathesis reactions including alkene, alkyne, and enyne metathesis. It then covers the key catalysts used, such as Grubbs and Schrock catalysts, as well as the 2005 Nobel Prize awarded for the development of metathesis reactions. The document concludes by outlining several important applications of metathesis in synthesizing biologically active compounds and natural products.
This document summarizes a seminar on photochemistry presented to the Department of Chemistry Post Graduation Center. The seminar covered various types of photochemical reactions including photoreduction, photoisomerization, photochemical substitution, photodimerization, and photolysis of carbonyl compounds. Photochemistry involves chemical reactions that are initiated by the absorption of light, most commonly in the visible or ultraviolet regions. A variety of reaction types such as reduction, synthesis, and isomerization can be induced photochemically. Examples of specific photochemical reactions discussed include the reduction of benzophenone to benzpinacol, photoisomerization of stilbene, and the Norrish Type I and II reactions of carbon
Nucleophilic substitution reactions are a class of reactions in which an electron rich nucleophile attacks a positively charged electrophile to replace a leaving group. For alginate reactions, the most reactive nucleophile is the C6 carboxylate group
This document provides details about Organic Chemistry II, a 2 unit course taught over two hours per week. The course content includes stereochemistry, functional group chemistry, substitution and elimination reactions. The document also provides a detailed lecture note on substitution reactions of alkanes, including halogenation reactions and their mechanisms via a free radical chain mechanism. It discusses the relative reactivities and stabilities of primary, secondary and tertiary positions during halogenation. Finally, it provides an overview of stereochemistry, including a discussion of enantiomers and chirality around tetrahedral carbons.
This document provides an overview of organic chemistry concepts including:
1) Classification of organic compounds such as hydrocarbons, functional group compounds, and aromatic compounds.
2) Isomerism including structural and stereoisomerism.
3) Bonding theories such as hybridization and resonance that explain organic compound structures and properties.
4) Reactions of organic compounds including substitution, addition, elimination, and oxidation reactions. Mechanisms such as electrophilic addition, free radical halogenation and the effects of stability and electronic effects are discussed.
Total synthesis of Sterpurenone New, Total Synthesis of (훽)-Cyperolone, Protecting Group-Free Total Synthesis of (−)-Lannotinidine B, Enantiospecific Total Synthesis of the (−)-Presilphiperfolan-8-ol, Enantioselective Total Synthesis of (−)-Pavidolide B, total synthesis of Eupalinilide E
This document summarizes the pinacol-pinacolone rearrangement reaction. It begins by defining the substrate as pinacols (1,2-glycols) and the reaction conditions as mineral acids or electrophilic reagents. It then explains that the reaction involves the formation of a carbocation intermediate and the migration of a nucleophilic group from a carbon to an electron-deficient carbon. The mechanism and factors affecting migratory aptitude are discussed. Applications include preparation of carbonyl compounds and spiroketones.
This document describes research into direct aldol reactions mediated by dimethylzinc. Three aromatic aldol products were synthesized and their NMR data reported. Racemic aldol products were produced using either dialkylzinc/dialcohol or magnesium bromide/DIPEA. Successful asymmetric and autocatalytic aldol reactions were also achieved using chiral catalysts. The products of some aldol reactions were found to facilitate their own formation and the reaction between other substrates, demonstrating autocatalytic properties. Further study of this autocatalytic process is warranted.
1) Alkenes are hydrocarbons that contain a carbon-carbon double bond. They include many naturally occurring compounds and important industrial materials.
2) The degree of unsaturation relates the molecular formula to possible structures by counting the number of multiple bonds or rings. Each double bond or ring replaces two hydrogens.
3) Alkenes react through electrophilic addition reactions, often involving a carbocation intermediate. The stability of the carbocation predicts the orientation of addition.
Molecular rearrangement reactions- Dr. Alka Tangri.pdfRaviansMotivations
This document discusses several types of rearrangement reactions in organic chemistry. It defines rearrangement reactions as reactions where a chemical unit such as an atom, ion, or group of atoms migrates within or between molecules of the same species to form a new product. The document discusses intramolecular and intermolecular rearrangements, and provides examples of anionotropic rearrangements like the pinacol rearrangement and cationotropic rearrangements like the Fries rearrangement. It also provides detailed mechanisms and applications of the pinacol rearrangement and Hoffman rearrangement.
The document discusses the concept of umpolung in organic chemistry, which is the reversal of polarity of a functional group through chemical modification. Specifically, it describes strategies for temporarily modifying carbonyl groups so that the carbon behaves as a nucleophile rather than an electrophile. Several methods are presented for generating equivalents of formyl and acyl anions, including using derivatives of 1,3-dithianes, nitroalkanes, cyanohydrins, enolethers, and lithium acetylides, which allow the "umpolung" of carbonyl reactivity and new disconnection pathways in retrosynthesis. An example of using a dithiane approach in the synthesis of the antibiotic vermic
The document discusses the production and properties of polypropylene. It describes how polypropylene is produced using Ziegler-Natta catalysts containing titanium and aluminum compounds. It then explains how newer metallocene catalysts allow for higher molecular weight polypropylene with more control over tacticity. The metallocene catalyst system uses a zirconium compound between two cyclopentadienyl ligands to regularly insert propylene monomers and produce isotactic polypropylene.
- Cu2O nanoparticles can catalyze C-C coupling reactions via either a homogeneous or heterogeneous pathway.
- In the presence of a base, the reaction proceeds through a homogeneous pathway where Cu complexes form in solution from leached Cu atoms.
- In the absence of a base, the reaction proceeds heterogeneously on the surface of the Cu2O nanoparticles without leaching.
- Characterization techniques provide evidence that the base facilitates leaching and homogeneous catalysis while no leaching occurs without the base, allowing truly heterogeneous catalysis.
This document summarizes several organic rearrangement reactions: the Cope rearrangement, Claisen rearrangement, and Curtius rearrangement. The Cope rearrangement involves the [3,3]-sigmatropic rearrangement of 1,5-dienes. The Claisen rearrangement is a carbon-carbon bond forming reaction that rearranges allyl vinyl ethers to γ,δ-unsaturated carbonyls. The Curtius rearrangement converts carboxylic acids to isocyanates through an acid azide intermediate. Mechanisms are provided for each reaction.
This document discusses addition reactions to carbon-carbon multiple bonds and carbon-heteroatom multiple bonds. It covers electrophilic, nucleophilic, and free radical addition to alkenes and alkynes. It also discusses addition reactions to carbonyl compounds, nitriles, imines, and sulfonyl chlorides. Reaction mechanisms, orientation, stereochemistry, and factors affecting reactivity are explained for various addition reactions. Important reactions like hydroboration, hydrohalogenation, hydration, oxidation, and reductions are also summarized.
Key concepts of Geometrical Isomerism useful for the Undergraduate and Postgraduate students of Pharmacy , Chemistry and Post graduates of Pharmaceutical and Medicinal Chemistry
This document provides an overview of homogeneous catalysis and biocatalysis. It discusses various homogeneous catalysts including Wilkinson's catalyst, Ziegler-Natta catalysts, and catalysts used in hydrogenation and hydroformylation reactions. It also discusses the use of enzymes in organic synthesis, including hydrolysis reactions and the synthesis of tartaric acids. Finally, it covers immobilized enzymes and various methods for enzyme immobilization.
Ppt on Organometallic Compounds-Zamir ShekhZAMIR SHEKH
The document discusses various types of organometallic compounds, including their definitions, nomenclature, properties, structures, and reactions. It describes organolithium, organomagnesium, organozinc, organocopper, and other organometallic compounds. It also discusses their applications in synthesis such as additions, displacements, conjugate additions, cyclopropanation, and opening of epoxides.
The video lecture for this presentation is available at the following link on YouTube
https://youtu.be/3sxal579RNM
The presenation will be useful for Ug/PG (Chemistry) students
The document defines and provides examples of various sigmatropic reactions, including:
1. The Claisen rearrangement, which involves the [3,3] rearrangement of an allyl vinyl ether.
2. The Cope rearrangement, which involves the [3,3] sigmatropic rearrangement of 1,5-dienes.
3. The Oxy-Cope rearrangement, which has a hydroxyl substituent and proceeds faster when deprotonated.
4. Other reactions discussed include the Fischer indole synthesis, aromatic Claisen rearrangement, [2,3]-Wittig rearrangement, Carroll rearrangement, and walk rearrangements. Mechanisms
This document discusses metathesis reactions and their applications in organic synthesis. It begins with definitions and examples of different types of metathesis reactions including alkene, alkyne, and enyne metathesis. It then covers the key catalysts used, such as Grubbs and Schrock catalysts, as well as the 2005 Nobel Prize awarded for the development of metathesis reactions. The document concludes by outlining several important applications of metathesis in synthesizing biologically active compounds and natural products.
This document summarizes a seminar on photochemistry presented to the Department of Chemistry Post Graduation Center. The seminar covered various types of photochemical reactions including photoreduction, photoisomerization, photochemical substitution, photodimerization, and photolysis of carbonyl compounds. Photochemistry involves chemical reactions that are initiated by the absorption of light, most commonly in the visible or ultraviolet regions. A variety of reaction types such as reduction, synthesis, and isomerization can be induced photochemically. Examples of specific photochemical reactions discussed include the reduction of benzophenone to benzpinacol, photoisomerization of stilbene, and the Norrish Type I and II reactions of carbon
Nucleophilic substitution reactions are a class of reactions in which an electron rich nucleophile attacks a positively charged electrophile to replace a leaving group. For alginate reactions, the most reactive nucleophile is the C6 carboxylate group
This document provides details about Organic Chemistry II, a 2 unit course taught over two hours per week. The course content includes stereochemistry, functional group chemistry, substitution and elimination reactions. The document also provides a detailed lecture note on substitution reactions of alkanes, including halogenation reactions and their mechanisms via a free radical chain mechanism. It discusses the relative reactivities and stabilities of primary, secondary and tertiary positions during halogenation. Finally, it provides an overview of stereochemistry, including a discussion of enantiomers and chirality around tetrahedral carbons.
This document provides an overview of organic chemistry concepts including:
1) Classification of organic compounds such as hydrocarbons, functional group compounds, and aromatic compounds.
2) Isomerism including structural and stereoisomerism.
3) Bonding theories such as hybridization and resonance that explain organic compound structures and properties.
4) Reactions of organic compounds including substitution, addition, elimination, and oxidation reactions. Mechanisms such as electrophilic addition, free radical halogenation and the effects of stability and electronic effects are discussed.
Total synthesis of Sterpurenone New, Total Synthesis of (훽)-Cyperolone, Protecting Group-Free Total Synthesis of (−)-Lannotinidine B, Enantiospecific Total Synthesis of the (−)-Presilphiperfolan-8-ol, Enantioselective Total Synthesis of (−)-Pavidolide B, total synthesis of Eupalinilide E
This document summarizes the pinacol-pinacolone rearrangement reaction. It begins by defining the substrate as pinacols (1,2-glycols) and the reaction conditions as mineral acids or electrophilic reagents. It then explains that the reaction involves the formation of a carbocation intermediate and the migration of a nucleophilic group from a carbon to an electron-deficient carbon. The mechanism and factors affecting migratory aptitude are discussed. Applications include preparation of carbonyl compounds and spiroketones.
This document describes research into direct aldol reactions mediated by dimethylzinc. Three aromatic aldol products were synthesized and their NMR data reported. Racemic aldol products were produced using either dialkylzinc/dialcohol or magnesium bromide/DIPEA. Successful asymmetric and autocatalytic aldol reactions were also achieved using chiral catalysts. The products of some aldol reactions were found to facilitate their own formation and the reaction between other substrates, demonstrating autocatalytic properties. Further study of this autocatalytic process is warranted.
1) Alkenes are hydrocarbons that contain a carbon-carbon double bond. They include many naturally occurring compounds and important industrial materials.
2) The degree of unsaturation relates the molecular formula to possible structures by counting the number of multiple bonds or rings. Each double bond or ring replaces two hydrogens.
3) Alkenes react through electrophilic addition reactions, often involving a carbocation intermediate. The stability of the carbocation predicts the orientation of addition.
Molecular rearrangement reactions- Dr. Alka Tangri.pdfRaviansMotivations
This document discusses several types of rearrangement reactions in organic chemistry. It defines rearrangement reactions as reactions where a chemical unit such as an atom, ion, or group of atoms migrates within or between molecules of the same species to form a new product. The document discusses intramolecular and intermolecular rearrangements, and provides examples of anionotropic rearrangements like the pinacol rearrangement and cationotropic rearrangements like the Fries rearrangement. It also provides detailed mechanisms and applications of the pinacol rearrangement and Hoffman rearrangement.
The document discusses the concept of umpolung in organic chemistry, which is the reversal of polarity of a functional group through chemical modification. Specifically, it describes strategies for temporarily modifying carbonyl groups so that the carbon behaves as a nucleophile rather than an electrophile. Several methods are presented for generating equivalents of formyl and acyl anions, including using derivatives of 1,3-dithianes, nitroalkanes, cyanohydrins, enolethers, and lithium acetylides, which allow the "umpolung" of carbonyl reactivity and new disconnection pathways in retrosynthesis. An example of using a dithiane approach in the synthesis of the antibiotic vermic
The document discusses the production and properties of polypropylene. It describes how polypropylene is produced using Ziegler-Natta catalysts containing titanium and aluminum compounds. It then explains how newer metallocene catalysts allow for higher molecular weight polypropylene with more control over tacticity. The metallocene catalyst system uses a zirconium compound between two cyclopentadienyl ligands to regularly insert propylene monomers and produce isotactic polypropylene.
- Cu2O nanoparticles can catalyze C-C coupling reactions via either a homogeneous or heterogeneous pathway.
- In the presence of a base, the reaction proceeds through a homogeneous pathway where Cu complexes form in solution from leached Cu atoms.
- In the absence of a base, the reaction proceeds heterogeneously on the surface of the Cu2O nanoparticles without leaching.
- Characterization techniques provide evidence that the base facilitates leaching and homogeneous catalysis while no leaching occurs without the base, allowing truly heterogeneous catalysis.
This document summarizes several organic rearrangement reactions: the Cope rearrangement, Claisen rearrangement, and Curtius rearrangement. The Cope rearrangement involves the [3,3]-sigmatropic rearrangement of 1,5-dienes. The Claisen rearrangement is a carbon-carbon bond forming reaction that rearranges allyl vinyl ethers to γ,δ-unsaturated carbonyls. The Curtius rearrangement converts carboxylic acids to isocyanates through an acid azide intermediate. Mechanisms are provided for each reaction.
This document discusses addition reactions to carbon-carbon multiple bonds and carbon-heteroatom multiple bonds. It covers electrophilic, nucleophilic, and free radical addition to alkenes and alkynes. It also discusses addition reactions to carbonyl compounds, nitriles, imines, and sulfonyl chlorides. Reaction mechanisms, orientation, stereochemistry, and factors affecting reactivity are explained for various addition reactions. Important reactions like hydroboration, hydrohalogenation, hydration, oxidation, and reductions are also summarized.
Key concepts of Geometrical Isomerism useful for the Undergraduate and Postgraduate students of Pharmacy , Chemistry and Post graduates of Pharmaceutical and Medicinal Chemistry
This document provides an overview of homogeneous catalysis and biocatalysis. It discusses various homogeneous catalysts including Wilkinson's catalyst, Ziegler-Natta catalysts, and catalysts used in hydrogenation and hydroformylation reactions. It also discusses the use of enzymes in organic synthesis, including hydrolysis reactions and the synthesis of tartaric acids. Finally, it covers immobilized enzymes and various methods for enzyme immobilization.
Ppt on Organometallic Compounds-Zamir ShekhZAMIR SHEKH
The document discusses various types of organometallic compounds, including their definitions, nomenclature, properties, structures, and reactions. It describes organolithium, organomagnesium, organozinc, organocopper, and other organometallic compounds. It also discusses their applications in synthesis such as additions, displacements, conjugate additions, cyclopropanation, and opening of epoxides.
The video lecture for this presentation is available at the following link on YouTube
https://youtu.be/3sxal579RNM
The presenation will be useful for Ug/PG (Chemistry) students
3. II. Carbon-carbon bond formation via nucleophilic
attack on a ligand.
ORGANOMET CHEM IN ORGANIC SYNTHESIS
4. III. Carbon-carbon bond formation via carbonyl or
alkene insertion.
ORGANOMET CHEM IN ORGANIC SYNTHESIS
5. IV. Carbon-carbon bond formation via transmetallation
reactions.
ORGANOMET CHEM IN ORGANIC SYNTHESIS
6. V. Carbon-carbon bond formation through cyclization
reactions.
ORGANOMET CHEM IN ORGANIC SYNTHESIS
7. The C=C and C=O undergoes transformations to variety of
organic compounds (alcohols, alkyl halides, alkanes).
The C=C and C=O are planar and achiral but in their reactions
creates one or more stereogenic centers in the reaction product.
Assymetric Hydrogenations
8. Methods of producing an enantiomer of a chiral
compound:
Chemical resolution of a racemate
Chiral chromatography
Use of a chiral natural products as starting material
Stoichiometric use of chiral auxilliaries
Asymmetric catalysis
Asymmetric Hydrogenations
9. Chiral chromatography:
- Use of chiral, enantioenriched groups to the solid
support
- In the chiral environment, the two enantiomers will
have diastereomerically different interactions with the
columns
ORGANOMET CHEM IN ORGANIC SYNTHESIS
10. Synthesis of biotin (involved in enzymatic transfer of
CO2):
ORGANOMET CHEM IN ORGANIC SYNTHESIS
11. Use of chiral auxiliaries:
ORGANOMET CHEM IN ORGANIC SYNTHESIS
12. Asymmetric Catalysis: same approach as the use of
chiral auxilliary except that the selectivity occurs
catalytically
The most environmentally benign approach to
enantioselectivity.
ORGANOMET CHEM IN ORGANIC SYNTHESIS
38. CARBON – CARBON BOND FORMATION VIA
NUCLEOPHILIC ATTACK ON AN 3 - ligand:
THE TSUJI-TROST REACTION
ORGANOMET CHEM IN ORGANIC SYNTHESIS
39.
40. TSUJI – TROST REACTION
Organic synthesis using allylic substrates:
unpredictable stereochemistry
poor control of regioselectivity
possible carbon- skeleton rearrangement.
Leaving groups for Tsuji-Trost Reaction
41. Tsuji-Trost Reaction:
With hard nucleophiles (pKa of conjugate acid >25)
results in an overall inversion of configuration at the
allylic site.
With soft nucleophile (pKa of conjugate acid < 25) react
to give retention of configuaration.
46. Several points in catalytic cycle where asymmetric
reaction could occur:
a) enantiomeric faces of the alkene
b) enantiomeric leaving groups
c) enantioface exchange in the 3 allyl complex
d) attack at enantiotopic termini of the 3 ally
ligand
e) Attack by different enantifaces of prochiral
nucleophiles.
ASSYMETRIC TSUJI – TROST REACTION
57. Heck Reaction – migratory C=C insertion
Step a ) OA
b) alkene coordination
c) migratory insertion of C=C
d) -elimination
Insertion is key step
R = aryl, alkyl, benzyl or allyl
X = Cl, Br, I, OTf
58. Rate of reaction and regioselectivity are sensitive to
steric hindrance about the C=C bond.
Rate of reaction varies according to:
Heck Reaction:
62. Also know as Cross Coupling Reaction:
C-C Bond Bond formation via Transmetallation Reactions
63. Transmetallation Reaction
Transmetallation Reaction – a method for introducing a -bonded hydrocarbon ligands
Into the coordination sphere transition metals.
The equilibrium is thermodynamically favorable from left to right if the
electronegativity of M is greater than that of M’.
77. Synthesis Application: The chemo-, regio-, and
stereoselectivity similar to those with Stille. Suzuki more
widely used for aryl-aryl coupling.
CROSS-COUPLING REACTION - SUZUKI
78. Cross coupling between alkynyl and aryl :
CROSS-COUPLING REACTION - Sonogashira
- Requires high loadings of Cu and Pd catalysts, relativelly hight
temperatures
- Cu-alkynes are formed in situ and then the alkyne is transferred
to Pd.