Brønsted Acid-Catalyzed Multicomponent Phosphonylation/Cyclization Strategy for the Synthesis of Phosphinylated 2H‑Isoindoles.

A Brønsted acid-catalyzed three-component modular phosphonylation/cyclization protocol has been established for the efficient synthesis of phosphinylated 2H-isoindoles, employing o-propargyl alcohol benzaldehydes, diarylphosphine oxides, and arylamines as starting materials. This metal-free cascade transformation is characterized by mild conditions, broad substrate compatibility, gram-scale synthesis, and one-pot construction of C-P, C-N, and CC bonds. Mechanistic studies revealed that this chemistry involves Kabachnik-Fields reaction, 5-exo-dig cyclization, and aromatization. Interestingly, these isoindole-substituted phosphine oxides emit bright fluorescence in the aggregated states under UV irradiation.