Transition Metal-Free <i>trans</i>-Selective Alkynylboration of Alkynes

We report the first transition metal-free and <i>trans</i>-selective alkynylboration reaction of alkynes. This unprecedented carboboration reaction is enabled by pseudo-intramolecular activation of alkynylboronates using propargylic alcohols. The carboboration affords 4-alkynyl-1,2-oxaborol-2­(5<i>H</i>)-ols, which are not only versatile building blocks but also exhibit strong violet-blue fluorescence emission