An efficient modular synthesis of conjugated ω-(p-hexyloxyphenyl)polyenals

Convenient precursors (alpha,beta -unsaturated aldehydes 1-5) for all-E conjugated omega-(p-hexyloxyphenyl)polyenals having two (15), four (16), five, (19), six (17) and eight (18) conjugated double bonds were synthesized in a modular synthesis using reactive silyl enol ethers [1-(trimethylsilyloxy)-1,3-butadiene or 1-(trimethylsilyloxy)-1,3,5-hexatriene)] as building blocks, and 5,5-diethoxypenta-2-enal (1) as a template. Polyene 8 containing three conjugated double bonds in its structure was obtained from omega-(p-hexyloxyphenyl)propenal (6) and butadienyl ethyl ether as starting materials.