Brønsted acid-promoted [3 + 3] cycloaddition of azomethine ylides with quinone monoimine: a practical method towards dihydrobenzoxazine derivatives†
Abstract
The binaphthol-derived phosphoric acid-promoted [3 + 3] cycloaddition of azomethine ylides with quinone monoimine has been achieved in the presence of 3 Å MS at room temperature, providing dihydrobenzoxazine derivatives in moderate to excellent yields.