Synthesis of aryl alkynyl carboxylic acids and aryl alkynes from propiolic acid and aryl halides by site selective coupling and decarboxylation

The coupling of propiolic acid with aryl iodides afforded the aryl alkynyl carboxylic acids and aryl alkynes in generally good yields. Aryl alkynyl carboxylic acids were obtained when the reaction was performed in the presence of Pd(PPh3)2Cl2 (2.5 mol %), dppb (5.0 mol %) and DBU (5 equiv) at 50 °C. For the synthesis of the terminal aryl alkynes, the reaction was conducted in the presence of Pd(PPh3)2Cl2 (2.5 mol %), dppb (5.0 mol %), DBU (5.0 equiv), and Cu(acac)2 (10 mol %) at 25 °C for 5 h, and further reacted at 60 °C for 6 h.