OXIDATIVE REARRANGEMENT OF BENZYLAMINES TO 4H-3,1-BENZOXAZINES VIA Cu/Mn-PROMOTED INTRAMOLECULAR C-H AMINATION/ELECTROCYCLIC REACTION CASCADE

摘要

We have developed a copper/manganese-mediated oxidative rearrangement of benzylamines to 4H-3,1-benzoxazines of potent interest in medicinal applications. The reaction proceeds uniquely through the initial copper/manganese-promoted intramolecular C-H amination giving benzazetidine intermediates and subsequent 4n electrocyclic ring opening/6 pi electrocyclic ring closing cascade. The key to success is the introduction of picolinamide-based N,N-bidentate directing group. The obtained benzoxazines can also be readily hydrolyzed to the corresponding 2-aminobenzyl alcohols, thus indicating that the overall transformations is regarded as the ortho-aminative rearrangement of benzylarnines to benzylic alcohols.