Formal γ−C−H Functionalization of Cyclobutyl Ketones: Synthesis of cis‐1,3‐Difunctionalized Cyclobutanes

Abstract

1,3‐Difunctionalized cyclobutanes are an emerging scaffold in medicinal chemistry that can confer beneficial pharmacological properties to small‐molecule drug candidates. However, the diastereocontrolled synthesis of these compounds typically requires complicated synthetic routes, indicating a need for novel methods. Here, we report a sequential C−H/C−C functionalization strategy for the stereospecific synthesis of cis‐γ‐functionalized cyclobutyl ketones from readily available cyclobutyl aryl ketones. Specifically, a bicyclo[1.1.1]pentan‐2‐ol intermediate is generated from the parent cyclobutyl ketone via an optimized Norrish‐Yang procedure. This intermediate then undergoes a ligand‐enabled, palladium‐catalyzed C−C cleavage/functionalization to produce valuable cis‐γ‐(hetero)arylated, alkenylated, and alkynylated cyclobutyl aryl ketones, the benzoyl moiety of which can subsequently be converted to a wide range of functional groups including amides and esters.