Chemistry Heterocyclic Building Blocks Pyridines 4-ethynylpyridine
Nucleophilic Substitution: The ethynyl group is electron-withdrawing, making the carbon atom partially electrophilic. This can undergo nucleophilic substitution reactions, where a nucleophile (e.g., a Grignard reagent) attacks the carbon atom, replacing the ethynyl group with a new substituent.
Acid-Base Reactions: The pyridine nitrogen is basic and can undergo acid-base reactions. It can act as a base, accepting a proton to form a pyridinium cation, or it can act as a nucleophile in reactions with electrophiles.
Alkylation/Acylation: The pyridine ring can undergo alkylation or acylation reactions at the nitrogen atom, typically under Friedel-Crafts conditions, where an alkyl or acyl group is added to the pyridine ring.
Metalation: The pyridine ring can coordinate with transition metal catalysts, leading to metalation reactions. This can facilitate further transformations, such as cross-coupling reactions.
Oxidation: The ethynyl group can undergo oxidation reactions to form corresponding carbonyl compounds or carboxylic acids, depending on reaction conditions.
Sonogashira Coupling: Given the presence of an ethynyl group, 4-ethynylpyridine can participate in Sonogashira coupling reactions with aryl halides or triflates, leading to the formation of substituted alkynes.
Reduction: Both the ethynyl group and the pyridine ring can undergo reduction reactions under appropriate conditions, leading to saturated or partially saturated derivatives.
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