Among numerous examples of direct C-H functionalization of ethers, Wan's condition exhibited PEO functionalization with low backbone degradation and gelation. The method involves the formation of a C-O bond between ether and carboxylic acid using tert-butyl ammonium iodide (TBAI) and tert-butyl hydrogen peroxide (TBHP), and it demonstrates simple operation and a broad substrate scope, including acyclic ethers (Scheme 2). The proposed mechanism involves the formation of an oxocarbenium intermediate from radical generation and oxidation by the TBAI catalyst, followed by the attachment of a nucleophilic carboxylic acid to form the desired C-O bond. The method's fully organocatalytic feature makes it highly desirable for medicinal applications.