Elucidation of a Sequential Iminium Ion Cascade Reaction Triggered by a Silica Gel-Promoted Aza-Peterson Reaction

In a recent methodological study investigating the synthesis of N-alkoxyazomethine ylides, an unexpected aminal byproduct was generated during our attempt to isolate O-benzyl-N-((trimethylsilyl)­methyl)­hydroxylamine. After a strategic investigation, silica gel was discovered to be the cause of the byproduct formation. Through the mechanistic insight from control and trapping experiments, we propose the formation of a methaniminium ion via a novel aza-Peterson reaction, which ultimately triggers a sequential iminium ion cascade sequence. Herein, we discuss the elucidation of this cascade reaction mechanism and the constraints for the byproduct formation.