Efficient and Practical Synthesis of β-Naphthol-Substituted 2-Azetines via Vinylidene ortho-Quinone Methide (VQM) Intermediates.

We report an efficient and practical strategy for the synthesis of bromo-substituted 2-azetines bearing a β-naphthol moiety. The reaction proceeds via the formation of highly reactive vinylidene ortho-quinone methide (VQM) intermediates, followed by intramolecular bromocyclization to afford highly strained 2-azetines under mild conditions. Notably, the cyclization step is significantly facilitated by catalytic Schreiner's urea. This protocol is readily scalable, and the strategically incorporated bromo group in the product provides a convenient handle for further derivatization.