Highly regio- and stereoselective preparation of Z-vinylboronates by a formal trans-hydroboration of terminal alkynes

We report an operationally convenient process for the preparation of Z -vinylboronates from terminal alkynes via a hydrozirconation/protonation procedure of in situ-generated 1-alkynylboronates with in situ-generated Schwartz's reagent (HCp 2 ZrCl). 1-Alkynylboronates are generated via reaction of lithiated alkynes with isopropyl pinacol borate, and Schwartz's reagent is generated conveniently by the slow reduction of ZrCp 2 Cl 2 with diisobutylaluminum hydride (DIBAL-H) at room temperature. • Clean, stereoselective access to Z -vinylboronate esters. • Successful direct synthesis of α,ω-bis( Z -vinylboronates) from α,ω-diynes. • Bypass isolation of sensitive 1-alkynylboronate ester intermediates. • Only one chromatographic purification step is required.