The spectral and chemical properties of potassium fluoride on activated alumina, an extensively used basic catalyst in organic synthesis, show that its unusually high reactivity relative to other fluoride-containing basic systems is due to the reaction of the fluoride ion with alumina to produce potassium hexafluoroaluminiate, potassium hydroxide and potassium aluminate. The reagent, more simply prepared from alumina and KOH, catalyzes the high-yielding addition of chloroform to m-nitrobenzaldehyde without producing Cannizzaro side-products. Fluoride ion is useful as a weakly basic, non-nucleophilic catalyst in many organic chemical processes involving hydrogen abstraction or hydrogen bond formation'. We judged that fluorides could be potentially useful as a basic catalyst in the addition of chloroform to m-nitrobenzaldehyde to replace classical methods employing hydroxide base which give large amounts of Cannizzaro side-reaction2. Sources of fluoride that have been previously used include alkali metal fluorides, tetra-alkylammonium fluoride salts and various solid supported systems'. Among the supported fluoride systems, potassium fluoride (KF) on activated alumina"-' has been found to be considerably and surprisingly more reactive than non-supported KF, KF-silica gel, KF-celite or KF-molecular sieves. The versatility of KF-alumina has been demonstrated a