Haloboration of internal alkynes with boronium and borenium cations as a route to tetrasubstituted alkenes

Hail boration! 2-Dimethylaminopyridine-ligated dihaloborocations [X 2B(2-DMAP)]+ with a strained four-membered boracycle were used for the haloboration of terminal and dialkyl internal alkynes (see scheme). Esterification then provided vinyl boronate esters as useful precursors to tetrasubstituted alkenes. Following mechanistic studies, the scope of the haloboration was expanded simply by variation of the amine. Pin=2,3-dimethyl-2, 3-butanedioxy. © 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of Creative Commons the Attribution Non-Commercial NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.