Fluorocyclization of 2‐Alkynylbenzoates: Synthesis of Fluorinated Isocoumarins by N‐Fluoropyridinium Salts

Abstract

Fluorocyclization of heteroatom‐centred nucleophile‐tethered unsaturated compounds is one of the most powerful methods for the synthesis of fluorinated heterocycles. However, although these reactions have often been accomplished by using transition metal catalysts along with fluorine sources, such catalytic systems have not been applicable to the reaction of 2‐alkynylbenzoates. Herein, we describe metal‐free fluorocyclization of 2‐alkynylbenzoates by N‐fluoropyridinium salts. The present method allows the selective synthesis of 4‐fluoroisocoumarins and 3,4,4‐trifluoroisochromanones by minor modification of the reaction conditions. This report provides one of the few methods for the synthesis of fluorinated isocoumarin.