9-[11C]heptadecan-9-one was synthesized from di-n-octylthexylborane via cyanidation with K11CN. The rearrangement of the organoborane intermediate followed by alkaline oxidation produced the title compound in 55-60 min from the end of bombardment (EOB) in 50-70% overall yield. The reaction sequence is applicable for the synthesis of various dialkyl ketones.