Summary: The hydroboration of 1-bromo-1-alkynes with allrylbromoboranes (RBHBr. SMe2), conveniently obtained via the controlled hydridation of alkyldibromoboranes (RBBrz* SMe2), followed by treatment with sodium methoxide produces B-(trans-1-alkyl-1-alkeny1) boronate esters that provide the corresponding trans alkenes on protonolysis and ketones on oxidation.