Supplementary Material A Demonstration of the Primary Stereoelectronic Effect in the Baeyer-

General Procedures. Unless otherwise noted, all manipulations were carried out under an i ert atmosphere (nitrogen or argon) in flame-dried glassware. Unless otherwise noted, all reaction solvents were dried according to literature procedures[1] immediately prior to use. Fluoroketones 5ax, 5eq and 12 were prepared according to literature procedures[2] and 9 was prepared by the same technique.[2,3] Commercial grade mCPBA was purified using the protocol described by Bortolini et al.[4] The exact purity was elucidated via iodometric titration. High-field NMR spectra were recorded on a Varian Unity Spectrometer (1H at 400 MHz, 13C at 100 MHz, 19F at 376.3 MHz). 1H, 13C and 19F NMR spectra were performed in CDCl3 containing 0.03 % TMS. 1H chemical shifts are reported in ppm relative to TMS (0 ppm). 13C chemical shifts are reported in ppm relative to CDCl3 (77.0 ppm). 19F chemical shifts are reported in ppm relative to the external standard C6H5CF3 (-65 ppm). Multiplicities in 1