Nitrosoarenes Implement Cascade Cyclization of 1-Allenyl-2-alkynylbenzenes through Diradical Mechanism

This work reports cascade cyclization between 1-allenyl-2-alkynylbenzenes and nitrosoarenes. When these two components reacted alone under N2, N,O-functionalized indane-fused isoxazolidines 3 were obtained selectively. DFT calculations verify that this reaction sequence involves unprecedented nitrone/alkyne cycloadditions, followed by diradical rearrangement.