Solvent-Switched Benzylic Methylene Functionalization: Addition, Ring-Opening, Cyclization, and Unexpected Cleavage of C–O and C–C Bonds

Intermolecular benzylic methylene functionalization of exo-cyclic enol ethers has been achieved using imines as reagents and potassium tert-butoxide as the catalyst. Depending on the solvent used, the reaction proceeds by two pathways. In THF, an addition/elimination reaction of exo-cyclic enol ethers with imines provides dihydroisobenzofuran derivatives in good yield. In DMSO, an addition/ring-opening/cyclization cascade reaction occurs with unexpected cleavage of C–O and C–C bonds, affording isoquinolin-1(2H)-one products in high yield under ambient reaction conditions.本研究以亚胺为试剂、叔丁醇钾为催化剂，成功实现了环外烯醇醚的分子间苄基亚甲基官能化反应。根据所用溶剂的不同，该反应可通过两条路径进行：在四氢呋喃（THF）中，环外烯醇醚与亚胺经加成/消除反应，以良好收率得到二氢异苯并呋喃衍生物；在二甲基亚砜（DMSO）中，则发生加成/开环/环化级联反应，伴随碳氧键与碳碳键的意外断裂，在室温反应条件下以高收率生成异喹啉-1(2H)-酮类产物。