Urea group-directed organocatalytic asymmetric versatile dihalogenation of alkenes and alkynes

The textbook alkene halogenation reaction establishes straightforward access to vicinal dihaloalkanes. However, robust catalytic methods to perform dihalogenation in a stereoselective manner are lacking, despite the ubiquity of contiguous halogen-bearing stereocentres in natural products, bioactive and pharmaceutical molecules. Here we show that a urea directing moiety judiciously installed on alkenes could anchor the halogen nucleophiles and thus circumvent the regioselectivity issue in this transformation. Additionally, common alkali halides could be used as halogenating reagents. Our organocatalytic strategy granted modular and streamlined access to diverse homo-/hetero-dihalogenation products with exquisite stereo- and regiocontrol, irrespective of the alkene geometry. Pseudoenantiomeric catalysts could relay chiral information in bromofluorination of isomeric alkenes, providing unified access to the full complement of stereoisomers. Extending this synthetic tactic to alkynes culminated in their atroposelective dihalogenation affording axially chiral alkenes.