A new entry of highly nucleophilic CHBr3–TiCl4–Mg system for the stereoselective synthesis of 1-alkenyl bromides

This TiCl4–Mg promoted coupling of CHBr3 with various aldehydes and ketones, especially in sterically hindered or enolizable ketones, provides a simple, practical, and stereoselective carbonyl–bromomethylenation leading primarily to (E)-vinyl bromides.