Anodic Fluorination of (Poly)Heteroaromatic Compounds in Conventional Organic Solvents and Ionic Liquids

摘要

Fluorinated aromatic heterocyclic compounds have been of much interest because of their unique biological properties.Although direct fluorination of heteroaromatic rings is the simplest way to prepare fluorinated heterocycles,successful examples of the fluorination are limited.For example,the chemical fluorination of five-membered heteroaromatic compounds such as pyrroles,thiophenes,and furans was attempted,however the yields were extremely low (less than 6%) and the selectivity was also unsatisfactory in all cases.Recently,electrochemical partial fluorination of organic compounds has been shown to be a new powerful method for selective fluorination.However,there have been few reports of direct fluorination of heteroaromatic compounds using an electrochemical method.In most cases,yields of the fluorinated products are extremely low or unsatisfactory.On the other hand,we found that electron-withdrawing groups promoted the anodic fluorination of heterocyclic compounds.With these facts in mind,we attempted the direct anodic fluorination of (poly) heteroaromatic compounds having various electron-withdrawing groups in conventional organic solvents and ionic liquids.