Abstract Propargyl aldehyde diethyl acetal (1, 1-diethoxy-2-propyne) and 2, 5-hexadiynal diethyl acetal (1, 1-diethoxy-2, 5-hexadiyne) have been successfully employed in the synthesis of the unsaturated aldehydes 2trans, 5cis-undecadienal, 2trans, 5cis, 8cis- tetradecatrienal and 2trans, 5cis, 8cis, 11cis-heptadecatetraenal, which were characterized as their 2, 4-dinitrophenylhydrazones.