Microwave-Assisted Synthesis of Fluorescent Pyrido[2,3-<i>b</i>]indolizines from Alkylpyridinium Salts and Enaminones

Abstract

Pyridinium ylides are well recognized as dipoles for cycloaddition reactions. In its turn, the microwave-assisted interaction of N-(cyanomethyl)-2-alkylpyridinium salts with enaminones unexpectedly proceeds as a domino sequence of cycloisomerization and cyclocondensation reactions, instead of a 1,3-dipolar cycloaddition. The reaction takes place in the presence of sodium acetate as base and employs benign solvents. The optical properties of the resulting pyrido[2,3-b]indolizines were studied, showing green light emission with high fluorescence quantum yields.

Keywords

• pyridinium ylide
• indolizine
• domino reaction
• fluorescence