Synthesis of isomeric 1,4-[13C]2-labeled 2-ethoxycarbonyl-1,4-diphenylbutadienes

The 1,4-bis-13C-labeled isomeric compounds (Z,E)- and (E,E)-2-ethoxycarbonyl-1,4-diphenylbutadiene have been synthesized by two different methods. A double Horner–Wadsworth–Emmons (HWE) strategy was employed for the synthesis of the Z,E isomer. On the other hand, synthesis of the E,E isomer was achieved by Baylis–Hillman reaction of benzaldehyde with ethyl acrylate and subsequent rearrangement, followed by Wittig olefination with benzaldehyde. These routes provide stereoselective access to labeled compounds in good yields.