Iron-Catalyzed Stereoconvergent Tertiary Alkylation of (E)- and (Z)-Mixed Internal Olefins with Functionalized Tertiary Alkyl Halides

Abstract

Herein, we report an efficient method for the stereoconvergent tertiary alkylations of (E)- and (Z)-mixed internal olefins (styrenes, enamides, and vinylic ethers) to produce trisubstituted olefins bearing a quaternary carbon center via an addition/elimination reaction in the presence of an iron catalyst. (E)- and (Z)-mixed internal olefins with various E/Z ratios reacted smoothly with α-bromocarbonyls as a tertiary alkyl source to exclusively produce (E)-trisubstituted olefins. Mechanistic studies revealed that each of the (E)- and (Z)-internal olefins exhibited the same reactivity, and the exclusive generation of (E)-trisubstituted olefin products could be attributed to the β-hydrogen elimination of an alkyl iron species. The developed method can be used to synthesize highly congested trisubstituted olefins containing a quaternary carbon atom that bears various alkyl chains.