1-Bromo-3-buten-2-one is investigated as a building block for organic synthesis. Reduction to the corresponding alcohol works best with lithium aluminium hydride, reaction with primary amines gives 5-membered-aza-heterocycles in moderate yields and reaction with activated methylene compounds to form 5-membered-carbocycles gave unsatisfactory yields when a one-pot-procedure was used. The first step of a stepwise protocol, a ...