Please login first
From Pyrylium to Pyridinium Salts: Understanding Physicochemical Features
* , ,
1  Departamento de Química Orgánica, Facultad de Química, Universidad de Sevilla, Spain

Abstract: Pyridinium salts are very useful synthetic building blocks to obtain substituted pyridine, dihydropyridine or piperidine. This synthetic strategy has been described for different applications such as total synthesis of Geissoschizine, cannabisativine, Lepadin B, among others. Pyridinium salts have been also used to achieve asymmetric and regioselective synthesis by additions of Grignard reagents. Furthermore, pyridinium salts have been applied as acylating agents, phase transfer catalyst or ionic liquid and dyes as a result of its intrinsic fluorescence. Frequently, these N-alkylated pyridine systems have been synthesized involving pyrylium salts as precursors. Pyrylium salts are cationic organic molecules with trivalent oxygen in a six member aromatic rings. These compounds have been exploited to design sensors for anions, amines, amino acids and chameleon labels for quantifying proteins. Herein, we report the synthesis and characterization of new 2,4,6-tri-arylpyrylium salts from small aldehydes and ketones. The synthesis of pyridinium salts by subsequent reaction with a primary alkyl amine or amino groups on carbohydrate moieties have been also explored. In one case, formation of pyridinium cation, that involves quaternary nitrogen, may provide a good potential candidate for gene delivery by using siRNA. We thank the AECID (Projects A/023577/09 and A/030422/10) and the 'Junta de Andalucía' (FQM 142 and Project P09-AGR-4597) for financial support.
Keywords: Pyridinium salts; pyrylium salts; amines; carbohydrates