Despite its usefulness, incorporating fluorine in organic molecules remains a synthetic challenge. Compared to their electrophilic counterparts, nucleophilic fluorinating reagents are less expensive. If not all, most fluorinating reagents electrophilic or nucleophilic, are made from HF. But HF itself is a gas and is difficult to handle. The complexes of HF with organic bases like Olah's reagent (pyridine-HF complex) and triethylamine-HF have been explored extensively as nucleophilic sources of fluorine. But these organic bases will also reduce the acidity of the system and may interfere with many metal catalysts. For example, pyridine can complex strongly with most transition metals and therefore reduce their activities.We found that HF and selected non-basic hydrogen bond acceptors can form stable complexes. These HF complexes can act as new nucleophilic fluorination reagents. They have higher acidity and these hydrogen bond acceptors do not interfere with most transition metal catalysts. We also found that our new nucleophilic fluorination reagents can behave as good or even better in classical nucleophilic fluorinations than even Olah's reagent. They can also be successfully applied in many modern transition metal catalyzed reactions.

Taming of the Shrew: Modulating HF reactivity through hydrogen bond basicity

248th National Meeting (2014)

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