Nickel‐Catalyzed Stereospecific Deoxygenation of trans‐ Aromatic Epoxides to (Z)‐Alkenes: An Efficient Route to Access (Z)‐Cinnamic Acid Derivatives

Abstract

AbstractA stereospecific deoxygenation of trans‐epoxy cinnamic acid derivatives to access (Z)‐cinnamamides, (Z)‐cinnamyl alcohol and (Z)‐cinnamyl amines using a catalytic system based on nickel triflate and triphenylphosphine has been developed. The desired products were obtained in good to excellent yield (up to 92 % isolated yield) and excellent stereospecificity (Z : E ratio up to>99 : 1). The transformation has a broad functional group tolerance including amides, amines, alcohols and esters. The power of the methodology was demonstrated in the key step of the total synthesis of biologically active natural product, N‐cis‐feruloyl tyramine from readily available trans‐ferulic acid. A reaction mechanism involving activation of epoxide via coordination of the oxygen atom and the neighboring O‐ or N‐atoms to the nickel catalyst and formation of Ph3P‐carbon bond is proposed. This method is important for synthesis of highly desirable functionalized (Z)‐alkenes from readily available (E)‐alkenes.