N-Fluoropyridinium Salt Fluorination for Preparing Aryl Fluorides

Introduction

As stated in the introduction part of the entry “N-Fluoropyridinium Salt Electrophilic Fluorination for Preparing Alkyl Fluorides,” three types of N-fluoropyridinium salts as fluorinating reagents have been developed, namely, a series of N-fluoropyridinium salts firstly developed as easy-to-handle, reactive, and widely applicable electrophilic fluorinating reagents (Fig. 1a) [6428,6429,6430,4], a series of zwitterionic N-fluoropyridinium-2-sulfonates as highly selective electrophilic fluorinating reagents (Fig. 1b) [5], and N,N’-difluoro-2,2’-bipyridinium salts as highly reactive fluorinating reagents with the high content of usable fluorine atom (Fig. 1c) [6]. In the first and the second series of N-fluoropyridinium salts, a number of reagents having different substituents, thus different fluorinating power, have been developed. The fluorination power of N-fluoropyridinium salts is closely dependent on the electron density of nitrogen atom of the pyridine ring....