Highly Regio- and Diastereoselective Formation of Tetrasubstituted (<i>Z</i>)‑1,2-Dihaloalkenes from the Halogenation of Trimethylsilyl Alkynes with ICl

The stereoselective <i>anti</i> addition of diatomic halogens to alkynes has been well studied. A method is reported that utilizes the β-silyl effect to override this typically observed <i>anti</i> selectivity and provides halogenation products that result from <i>syn</i> addition. The reaction involves the addition of iodine monochloride to trialkylsilyl-substituted alkynes to produce tetrasubstituted (<i>Z</i>)-dihaloalkenes in good to excellent yields and with excellent regio- and diastereoselectivity