S1 Table of contents Experimental section S2 General information S2 Synthesis and characterization of catalysts 1a, 12a-e S2 Synthesis and characterization of alkenes 3b-r S13 Enantioselective cyclopropanation and characterization data for 4c-t S18 Synthesis and characterization of alkylpyridinium salts 5a-h S28 Baeyer-Villiger reaction S31 Steglich rearrangement S34 Screening of cyclopropanation conditions S36 Kinetic data S38 Determination of the half-life of the formation of 5a,c,e,f,h S39 Determination of the cyclopropanation half-life starting from 5a-g S41 Determination of the cyclopropanation half-life starting from 7a-h S43 Fluorescence polarization assay S47 X-Ray structure, crystal data and structure refinements for (S)-1a S50 X-Ray structure, crystal data and structure refinements for (2S,3R)-4h S51 X-Ray structure, crystal data and structure refinements for (2R,3S)-4t S52 DFT calculations S53 Calculations of methyl cation affinities S54 Optimized geometries S55 1H NMR, 13C NMR, 19F NMR and IR data S68 Chiral stationary phase HPLC data S175