Organic Chemistry - Heterocyclic Compounds - Pyridine II.pdf

Organic Chemistry Heterocyclic Compounds Pyridine | Lec.18 Pyridine Contents : N-Additions of various Lewis acids to pyridine 3 Pyridine N-Additions of various Lewis acids to pyridine: Lewis Acids easily are easily added to the nitrogen atom of pyridine forming salts (pyridinium). This creates a pos...

Organic Chemistry Heterocyclic Compounds Pyridine | Lec.18 Pyridine Contents : N-Additions of various Lewis acids to pyridine 3 Pyridine N-Additions of various Lewis acids to pyridine: Lewis Acids easily are easily added to the nitrogen atom of pyridine forming salts (pyridinium). This creates a positive charge in the ring that increases the reactivity of pyridine to both oxidation and reduction reaction. Pyridine Also for piperidine, ammonia, primary and secondary amines are especially powerful catalysts for the Michael addition. They appear to play a specific role in this reaction: not just to abstract a proton from the reagent (α-hydrogen from α-carbon) to generate a carbanion, but to react with the carbonyl group of the substrate( α,β-unsaturated carbonyl carbon) to form an intermediate imine or iminium ion that is particularly reactive toward nucleophilic addition. Pyridine Iminium Pyridine Other names of pyridine are azine or azabenzene. It is present in many compounds like azines or vitamins (niacin and pyridoxal). Increased demand for pyridine resulted in the development of more economical methods of synthesis: Acetaldehyde + Ammonia → pyridine