Synthesis of fluorhydrins by reaction of quinidine acetate, epiquinidine, and its acetate in superacid

In HF–SbF5, with or without H2O2, a source of ‘OH+’ equivalent, quinidine 1a yields three ethers, the preferred conformation of the substrate favoring the observed cyclization. Under similar conditions, quinidine acetate 1b, epiquinidine 2a, and its acetate 2b give fluorhydrins with or without rearrangement in different amounts according to the nature of the substrate and the acidity. At low acidity, epiquinidine 2a yields selectively a sole nonrearranged fluorhydrin 10a. Quinidine acetate 1b, at high acidity, yields only rearranged fluorhydrins 8b and 9b.

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