The synthetic method of tetraphenyl‐substituted all‐E‐carotenes 1 with improved properties of antioxidant and molecular electronic conductance was developed through the formation of tetraphenyl‐substituted all‐E‐apocarotenedial 4. The synthesis highlighted the preparation of novel subunits containing phenyl substituent(s) with E‐configuration starting from the key (E)‐4‐chloro‐2‐phenylbut‐2‐enal (10), utilizing conjugation effect with formyl group or easy recrystallization of sulfone compounds. Sulfone‐mediated coupling methods of Julia and modified Julia–Kocienski olefinations utilizing the subunits were demonstrated to produce tetraphenyl‐substituted apocarotenedials 4. The major all‐E‐forms (73–85 % selectivity) were easily purified by SiO2 chromatography and trituration with Et2O due to the presence of the polar formyl groups. The olefination of all‐E‐apocarotenedials 4 and Wittig salt 5 provided all‐E‐9,9',13,13'‐tetraphenylcarotenes 1.

Practical synthetic methods of biogenetically and pharmaceutically important phytofluene were developed through divergent preparation of key C20 substrates from a common intermediate and convergent synthesis by Wittig and Julia-Kocienski olefinations. Expeditious synthesis of phytofluene was also proposed based on the Julia sulfone-mediated chain-extension and double elimination method. Stereochemical outcomes of these olefination methods for phytofluene were compared and the Julia-Kocienski method was the mildest and most efficient reaction condition to produce all-(E)-phytofluene. Complete 1H- and 13C-NMR analysis of all-(E)-phytofluene was reported for the first time. Phytofluene underwent facile thermal isomerization to other Z-isomers above room temperature, which was also confirmed by the C30 phytofluene homologue.