Nfluorobenzenosulfonimid

N-fluorobenzenesulfonimide, commonly abbreviated as NFSI, is an electrophilic fluorinating reagent used to transfer fluorine to a wide range of organic substrates. It is the N-fluorinated derivative of benzenesulfonimide, featuring a fluorine atom bonded to nitrogen that is connected to two sulfonyl-phenyl groups. In practical terms, NFSI serves as a convenient source of electrophilic fluorine (F+) under mild conditions, enabling the formation of C–F bonds in diverse chemical settings.

NFSI is widely employed in modern organic synthesis for C–H fluorination, benzylic and allylic fluorination, and aryl fluorination, often in conjunction with metal catalysts such as copper, nickel, or iron, as well as in photoredox or metal-free protocols. The reagent can enable late-stage fluorination of complex molecules, contributing to pharmaceutical and agrochemical development by installing fluorine atoms without demanding harsh conditions. Its solid and often air-stable nature makes it a practical choice for laboratory use and scale-up.

Mechanistically, NFSI can act as a source of electrophilic fluorine and, in some reactions, participates through radical or ionic pathways that generate fluorinated products with varying degrees of selectivity. The scope spans arenes, alkenes, and heteroatom-containing substrates, with reaction conditions tuned to achieve the desired regio- and stereoselectivity.

NFSI is commercially available from chemical suppliers and is used under standard laboratory safety practices. It is an irritant and should be handled in a well-ventilated hood with appropriate personal protective equipment. Store in a cool, dry place away from incompatible materials.