A mild, efficient, and transition-metal-free three-component coupling reaction involving arynes, phosphites, and aldehydes was established to afford 3-mono-substituted benzoxaphosphole 1-oxides. A range of 3-mono-substituted benzoxaphosphole 1-oxides was obtained from both aryl- and aliphatic-substituted aldehydes in moderate to good yields. Moreover, the synthetic utility of the reaction was demonstrated by a Gram-scale reaction and the transformation of the products into various P-containing bicycles.