We describe a convenient preparation of 4,6,6-trimethyl-1,3,2-dioxaborinane (MethylPentaneDiolBorane, MPBH) and demonstrate that it is an excellent reagent for the [PdCl 2 (PPh 3 ) 2 ]-catalyzed borylation of aryl bromides and iodides. The corresponding boronic esters undergo rapid Su-

Methylpentanediolborane (MPBH) 1 can be prepared easily by reaction of hexyleneglycol with BH3/DMS or B2H6 generated from NaBH4 and I2. MPBH hydroborates stereo- and regioselectively highly functionalized alkynes, including propargyl bromide and propionaldehyde acetal. MPBH compares favorably with pinacolborane in terms of reactivity. The obtained vinylboronic esters are air- and chromatography-stable.