Acyclic Oxyiminium Ions. Mannich Reactions and Addition of Grignard Reagents

Acyclic oxyiminium ion generation from secondary hydroxylamines (4a,b and 6a,b) and formaldehyde in the presence of acetic acid is reported. Trapping these electrophiles with 2-methyl furan, pyrrole or indole affords a series of novel O-benzyl tertiary hydroxylamines in good to excellent yield. Benzotriazole mediated synthetic methodology has also been successfully developed to generate oxyiminium ions which react with Grignard reagents, to give novel O-benzyl tertiary hydroxylamines.