Synthesis of 2-Propanoyl-5-Norbornene in Pyridinium Ionic Liquids Catalyzed by Yttrium Salts

Pyridinium salts: from synthesis to reactivity and applications

This review highlights the pyridinium salts in terms of their natural occurrence, synthesis, reactivity, biological properties, and diverse applications.

A Simple, Effective, Green Method for the Regioselective 3-Acylation of Unprotected Indoles

A fast and green method is developed for regioselective acylation of indoles in the 3-position without the need for protection of the NH position. The method is based on Friedel-Crafts acylation using acid anhydrides. The method has been optimized, and Y(OTf)₃ in catalytic amounts is found to be the best catalyst together with the commercially available ionic liquid [BMI]BF₄ (1-butyl-3-methylimidazolium tetrafluoro-borate) as solvent. The reaction is completed in a very short time using monomode microwave irradiation. The catalyst can be reused up to four times without significant loss of activity. A range of substituted indoles are investigated as substrates, and thirteen new compounds have been synthesized.