Fluorination of carbanions is pivotal for the synthesis of fluorinated compounds. Despite the existence of a vast number of fluorinating reagents, the fluorination of highly basic carbanions such as organo lithiums is still problematic, mainly because of the many undesired reactive sites present in these reagents themselves. Thus, we developed a novel reagent, N-fluoro-N-(tert-butyl)-tert-butanesulfonamide (NFBB), consisting of the smallest possible fluorine core, -SO2NF-, sandwiched between two bulky inert tert-butyl groups. NFBB can fluorinate highly basic (hetero)aryl and alkenyl lithium species in unprecedented high yields. With NFBB, we also discovered a conceptually new self-sustaining fluorination methodology toward active methylene compounds. Instead of requiring equimolar amounts of strong bases or environmentally unfriendly metals, our self-sustaining fluorination-deprotonation reaction cycle needed only a catalytic amount of Cs2CO3. NFBB was prepared in excellent yield using N-fluorobenzenesulfonimide (NFSI), under conditions that are well suitable for laboratory preparation; It was also prepared in good conversion yield using F2/N2—an industry preferred fluorine source. NFBB is stable, easy-to-handle, and purified by simple distillation (bp 61.5~62 oC/9.5~10.1 mmHg). Its easy preparation and purification make NFBB a chemical suitable for large scale production in a factory. This presentation will showcase the wide application of NFBB to prepare many useful fluorinated compounds in a highly effective manner.

Self-sustaining and highly selective fluorination of carbanions with N-fluoro-N-(tert-butyl)-tert-butanesulfonamide: New solutions to old problems

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