Halodeboronation of organotrifluoroborates using tetrabutylammonium tribromide or cesium triiodide

Halodeboronation of organotrifluoroborates using commercially available tetrabutylammonium tribromide (TBATB) or cesium triiodide in aqueous medium is reported. The mild, transition metal-free method has proven to be tolerant of a wide range of functional groups. High regio- and chemoselectivity are observed. Two synthetic routes to (Z)-dibromoalkenes from alkynes, through stereodefined (Z)-2-bromoalkenyltrifluoroborates and (Z)-1,2-bis(boryl)alkenyltrifluoroborates, have been developed using the TBATB mediated bromodeboronation as the key step.