Sandmeyer and Dieckmann Reactions (G).pptx

Sandmeyer and Dieckmann reactions in organic synthesis . Named reactions of advanced organic chemistry (M.pharm) based.

1. Sandmeyer & Dieckmann Reaction Presented by – Garima Singh Masters Of Pharmacy 1 st Year Department of Pharmaceutical Chemistry (Organic Chemistry)

2. Contents Sandmeyer Reaction Introduction Characteristics General Reaction Reaction Mechanism Applications Dieckmann Reaction Introduction Characteristics Basic Reaction Proposed Mechanism Applications

3. Introduction Sandmeyer reaction is used to synthesize diazonium salts using copper salts as reagents or catalysts . This reaction provides a method through which unique transformations on benzene can be performed , such as halogenation , cyanation , trifluoromethylation and hydroxylation. Aniline Aryl halide The reaction was discovered in 1884 by Swiss chemist Traugott Sandmeyer . This reaction is an example of radical- nucleophillic aromatic substitution. SANDMEYER REACTION

4. Characteristics This reaction is a type of substitution reaction that replaces an amino group on an aromatic ring with a variety of substituents . Copper salts like chloride, bromide or iodide ions are used as catalysts. Sandmeyer reaction is a two step process that involves preparing of diazonium salt of an aromatic amino group then displacing the diazonium salt with a nucleophile . It is a versatile synthetic tool that can be used to produce aryl halides.

5. General Reaction Formation of aniline - benzene nitrobenzene aniline Formation of aryl halides – Aniline diszonium salt aryl halide

6. Reaction Mechanism Protonation takes place to form nitrosonium and halide ions by the reaction of sodium nitrite with hydrogen halide. Sodium nitrite Hydrogen halide Nitrosonium Sodium halide Conversion of amine into diazonium salt by the electrophillic nitrosonium . aniline nitrosonium Benzenediazonium

7. Mechanism….. Single electron transfer from copper to the diazonium & from halide to Cu (1) halide ion to form a neutral diazo radical and Cu (2) halide. Cu (1) halide Benzenediazonium Diazoradical Cu (2) halide Release of nitrogen gas by the diazo radical to form an aryl radical which reacts with the Cu (2) halide then it regenerate Cu (1) halide and form the final aryl halide. Diazoradical Cu (2) halide Aryl halide Cu (1) halide

8. Applications Synthetic – Variations on the Sandmeyer reaction have been developed to fit multiple synthetic applications . These reactions typically proceed through the formation of aryl diazonium salt . Hydroxylation : This reaction can also be used to convert aryl amines to phenols .

9. Applications…… General – Sandmeyer reaction can be used to create chlorides, bromides, and iodides. Formation of Benzonitriles . It can be used in the synthesis of neoamphimedine , ( a compound that is used as an anticancer drug. Trifluoromethylated compound can be created by this reaction. Used to convert aryl amines to phenols .

10. Introduction Dieckmann condensation is the intramolecular chemical reaction of diesters with base to give β - keto esters. This reaction is named after the German chemist Walter Dieckmann (1869 – 1925 ) The equivalent intermolecular reaction is the Claisen condensation. Diesters beta keto esters A chemical reaction that produces β - keto esters from diesters in the presence of a base. DIECKMANN REACTION

11. c haracteristics This is a intramolecular condensation reaction. This reaction is simmilar to Claisen condensation. It involves deprotonation of an ester , generation of enolate ion , and nucleophillic attack to produce a cyclic enol . Dieckmann reaction is most effective for producing 5- , 6- , and 7-membered rings . It is usually performed in an alcoholic solvent with sodium alkoxide .

12. Basic Reaction Diesters β - keto alcohol esters n represents the number of Carbon Example:- Diethyl heptadioate Diethyl heptadioate 2- Propanoyl ethanol cyclohexanone

13. Proposed Mechanism 1.) Diester group will react with a base and there will be a formation of a Carbanion . Diesters Base 2.) The resulting Carbanion then attacks the carbonyl carbon of the other ester group. ( intramolecular nucleophillic attack ) .

14. Mechanism….. 3.) In next step there will be the removal of base. 4.) Formation of final Cyclic β - ketone Cyclic beta- ketone

15. Applications Synthetic – Synthesis of steroid – donor acceotor New C-C bond

16. Application General – Used in the synthesis of various cyclopentanone and cyclohexanone derivatives and has been used to build 5- or 6- membered rings in various natural products . Can be used to synthesize cyclic ketones and other large ketone molecules from β - ketoesters . This reaction is used in the preparation of cyclic indole { active against cancer } .

17. Refrence Name Reactions and Reagents in organic synthesis (second edition). Bradford P. Mundy , Michael G. Ellerd , Frank G. Favloro , Jr. (pg. no. – { Dieckmann reaction : 204 , Sandmeyer reaction : 570 } ) . Comprehensive Organic name Reactions and Reagents , John Wiley and Sons (pp: 2471 – 2475 ). Davis , B. R . ; Garret , P . J . Comprehensive organic synthesis . 1991 , 2 . 806 – 829 . (Review) .

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