5-Bromopentadienal 1b (n= 2), easily obtained from the potassium glutaconaldehyde salt, is used as precursor of ω-bromoheptatrienal 1d, ω-bromomethoxyhexatriene 2, diene diols 4, diene diones 5, 1, 6-dibromohexa-1, 3, 5-triene 6 and 1, 8 triene diol 8, of controlled configuration.