Reductive coupling of benzyl oxalates with highly functionalized alkyl bromides by nickel catalysis.

ABSTRACT

Coupling reactions involving non-sulfonated C-O electrophiles provide a promising method for forming C-C bonds, but the incorporation of functionalized or secondary alkyl groups remains a challenge due to the requirement for well-defined alkylmetal species. In this study, we report a reductive nickel-catalyzed cross-coupling of benzyl oxalates with alkyl bromides, using oxalate as a new leaving group. A broad range of highly functionalized alkyl units (such as functional groups alkyl chloride, alcohol, aldehyde, amine, amide, boronate ester, ether, ester, heterocycle, phosphonate, strained ring) were efficiently incorporated at the benzylic position. The utility of this synthetic method was further demonstrated by late-stage modification of complex bioactive compounds. Preliminary mechanistic experiments revealed that a radical process might be involved in the reaction.