Procedure for the synthesis of 1,3,5-triethynylbenzene: To a flame-dried flask under argon protection was added 1,3,5-tris((trimethylsilyl)ethynyl)benzene (2.39 mmol, 1 eq.), cesium carbonate (4.78 mmol, 2 eq.) and methanol (10 mL). The reaction mixture was stirred for 16 hours. Upon completion of the reaction, the solution changed from opaque to translucent. Methanol was removed by distillation under reduced pressure and the residual solid was partitioned between water and dichloromethane. The aqueous layer was extracted with dichloromethane (3 x 20 mL). The combined organic layers were washed sequentially with aqueous ammonium chloride (1.0 M, 2 × 20 mL), water (2 × 20 mL) and brine (2 × 20 mL). The organic layer was dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford the off-white soft crystal-like product 1,3,5-triethynylbenzene (2.09 mmol) in 87% yield with a melting point of 101-103 °C. The product was obtained by 1H NMR. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3) δ 7.57 (s, 3H), 3.12 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 135.6, 122.8, 81.6, 78.7; MS (CI+) m/z 151 [M]+.
