Microwave Irradiation Assisted Afficient Multi-component Synthesis Of Polysubstituted Pyridines

The pyridyl heterocyclic core is a widespread subunit in numerous natural products and pharmaceuticals. The polysubstituted pyridines, especially terpyridines are also prominent building blocks in coordination and supramolecular chemistry with their nitrogen-complexing andπ-stacking and directional H-bonding ability. These facts consequently provide a continue interests for developing new efficient synthetic procedure of pyridines. Polysubstituted pyridines have been synthesized by using various methods and procedures. The special nature of pyridinium cations allows them to be used in a great variety of synthetic reactions and they has become good reagents to synthesize versatile heterocycles. In this thesis we wish to report our study on the multi-component one-pot reactions of pyridinium salts to prepare some pyridine derivatives. A series of significant results and developments have been achieved and the main interesting results are as follows: 1. The microwave irradiation reaction of N-phenacylpyridinium chloride with chalcone in the mixture of ammonium acetate and acetic acid to give 2, 4, 6-triarylpyridines in high yields. A mixture of aromatic aldehyde and substituted acetophenone can be used to replace chalcone to react with N-phenacylpyridinium chloride and 2, 4, 6-triarylpyridines can be also prepared. Under similar reaction bipyridyl and pyrazolylpyridine derivatives are also synthesized by one-pot reactions. N-phenacylpyridinium chloride reacts with two molar aromatic aldehydes in a mixture of ammonium acetate and acetic acid via a Mannich-type reaction to give 2, 4, 6-triarylpyrimidine.2. Under mentioned microwave irradiation conditions N-phenacylpyridinium chloride reacts with 2 mol of aromatic aldehydes and 1 mol of cyclic ketones such as cyclopentanone, hexanone, and piperidinone to give the cyclo-fused pyridines with an additional benzylidene group. In the absence of pyridinium salt, cyclic ketones react with aromatic aldehydes with 2:3 molar ratios to give bicycle-fused pyridine with two additional benzylidene groups. The structures of all products are confirmed by single X-ray diffraction of five representative compounds.3. Under microwave irradiation, N-cyanomethylpyridinium chloride reacted with chalcone or with a mixture of aldehyde and ketone in the presence of ammonium acetate and acetic acid to give 2-amino-4, 6-diarylpyridines in high yields. N-(ethoxycarbonyl methyl)pyridinium chloride reacts with aromatic aldehydes and substituted acetophenones to give 4,6-diaryl-2-pyridinones, while reacts with aromatic aldehydes and cyclic ketones to give 2-quinolinone derivatives.