K₂S₂O₈-mediated metal-free direct P–H/C–H functionalization: a convenient route to benzo[b]phosphole oxides from unactivated alkynes

A metal-free and K₂S₂O₈-mediated radical addition/cyclization of internal alkynes leading to benzo[<italic>b</italic>]phosphole oxides was developed, which eliminates residual heavy metal contamination in the product.