Electrooxidative C‐C Fragmentation of Aromatic Radical Cations for Cascade Benzylic Multifunctionalization

Abstract

ABSTRACT Oxygen, nitrogen, and halogen‐containing functional groups are ubiquitous in complex small molecules. The installation of multiple carbon‐heteroatom bonds by the simultaneous functionalization of contiguous C–H/C–C bonds in a selective fashion is highly desirable in polymers degradation, skeletal editing, and petroleum cracking. However, achieving simultaneous, multi‐site functionalization of relatively inert C–C/C–H bonds with precise control over site‐, regio‐, and oxidation‐state selectivity remains challenging, particularly due to competing overoxidation and decomposition. Here we report the electrooxidative selective C‐C fragmentation of aromatic radical cations for cascade benzylic di‐ and trifunctionalization in simple alkylarenes by iterative dehydrogenation and oxygenation. Central to our approach is the controlled formation of olefin intermediates in situ at a rate carefully balanced to prevent polymerization and overoxidation. This strategy provides efficient access to diverse, high‐value di‐ or trifunctionalized products, including di‐ and triacetates, 2‐oxazolines, 1,2‐dibromoethanes, 1,3‐dibromo‐2‐ols, and 2‐(bromomethyl)oxiranes via controlled 4‐electron, 6‐electron, or 10‐electron oxidation events. Notably, the selective synthesis of di‐ versus trifunctionalization products is readily controlled through judicious choice of acids and nucleophiles.