Lithium acetylides with functional groups such as orthoester or acetal group in the molecule react with trialkylboranes with the migration of alkyl groups. The oxidation of the intermediates obtained from triethyl orthopropiolate gives a mixture of β-hydroxy-and α,β,-unsaturated esters, and the oxidation of those from propiolaldehyde diethylacetal gives (E)-1-ethoxy-1-alken-3-ones respectively.