Regio- and stereoselective synthesis of 1-(1-halovinyl)-1H-indoles from 1-ethynyl-1H-indoles with in situ generated HX

A facile approach to 1-(1-halovinyl)-1H-indoles from readily accessible 1-ethynyl-1H-indoles with in situ generated HX is described. The simple protocol enables a regio- and stereoselective hydrohalogenation to the triple bonds in gram-scale, and provides a general entry for novel N-alkenylindole derivatives.