1Z,5Z-diene compounds containing biologically active 3,4-dimethoxyphenyl fragments were synthesized. Molecules containing this moiety have attracted the attention of medicinal chemistry researchers due to their biological activities, including anti-inflammatory and antioxidant, anticancer, fungicidal and neuroprotective activities. The presence of methoxy groups in these structures enhances their biological activity as they participate in various interactions that are critical for their binding affinity and selectivity towards certain biological targets. The intermolecular homo-cyclomagnesiation reaction of 4-(buta-2,3-dien-1-yl)-1,2-dimethoxybenzene catalyzed by Cp2TiCl2 with the help of EtMgBr produced dialkylidenemagnesacyclopentane, the acid hydrolysis of which led to the production of (2Z,6Z)-1,8 -bis(3,4-dimethoxyphenyl)octa-2,6-diene with a yield of 74%. Also, Ti-catalyzed cross-intermolecular cyclomagnesiation of 4-(buta-2,3-dien-1-yl)-1,2-dimethoxybenzene with octadeca-1,2-diene produces the corresponding dialkylidenemagnesacyclopentane, acid hydrolysis of which gives the target 1,2- dimethoxy-4-((2Z,6Z)-pentacose-2,6-dien-1-yl)benzene in 68% yield. Cyclomagnesiation reactions were carried out in an inert atmosphere of argon. The resulting products were isolated using column chromatography. The structures of the synthesized compounds were determined using elemental analysis, IR, 1H-NMR, 13C-NMR spectral data and mass spectroscopy. The resulting 1Z,5Z-dienes containing 3,4-dimethoxyphenyl fragments are of great interest as objects for studying their biological activity.