It is commonly assumed that the relative hydrogen-bond basicity of an organic compound bears a simple correlation with its Brønsted basicity (pKaH+, pKa of its conjugate acid); however, this assumption holds true only for structurally related compounds. Hydrogen-bond basicity (measured by pKBHX) provides a complementary approach to gauge H-bond strength. Our premise is that a strong (good) hydrogen bonding acceptor (HBA) is not necessarily a strong base (Brønsted or Lewis base). In other words, a weak base is not necessarily a weak hydrogen bond acceptor. This premise has allowed us to discover new good hydrogen bonding acceptors which are weak bases but capable of complexing with HX (F, Cl, Br), delivering HX-based nucleophilic halogenation reagents that work well in acid or transition metal catalyzed reactions. This presentation will show our more recent advances using HF-DMPU and other complexes of HX.

Recent advances in hydrogen bond-controlled nucleophilic fluorination

253rd National Meeting (2017)

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