Synthesis of Azide-Functionalized Tetraphenylethene

Azide-functionalized tetraphenylethene (TPE-N₃) was synthesized in two steps with an 80% total yield. (1) Synthesis of 1-(4-methylphenyl)-1,2,2-triphenylethene. To a 250 mL two-necked round-bottom flask equipped with a stirring bar, 5.05 g (30 mmol) of diphenylmethane was added and dissolved in 100 mL of anhydrous THF. Then, the mixture was cooled down to 0 °C, and 15 mL (2.5 M in hexane, 37.5 mmol) of n-butyllithium was slowly added by a syringe. The mixture was stirred at 0 °C for 1 h. Next, 4.91 g (25 mmol) of 4-methylbenzophenone was added into the flask, and the mixture was warmed to room temperature and stirred overnight. The reaction mixture was then quenched with saturated NH₄Cl solution and subsequently extracted with DCM (three times). Organic layers were collected and concentrated on a rotary evaporator under reduced pressure. The crude product with 0.20 g of p-toluenesulfonic acid was dissolved in 100 mL of toluene. The mixture was heated and refluxed for 4 h. After cooling to room temperature, the mixture was extracted with DCM (three times). The organic layers were collected and concentrated. The crude product was analyzed with LC–MS (purity > 95%) and was used in the next step without purification (4.08 g, 95% yield). HR-MS (MALDI-TOF): m/z 346.1701 [(M)+, calc. 346.1722]. (2) Synthesis of 1-[(4-bromomethyl)phenyl]-1,2,2-triphenylethene. In a 250 mL round-bottom flask, a mixture of 3.04 g (8.77 mmol) of 1, 1.80 g (9.77 mmol) of freshly recrystallized N-bromosuccinimide, and 0.025 g of benzoyl peroxide in 60 mL of CCl₄ was refluxed for 12 h. After this time, the mixture was extracted with water and DMC (3×). The organic layers were combined and dried over magnesium sulfate, and the DCM was removed under reduced pressure. The crude product was purified by silica-gel chromatography using hexane as the eluent to yield 2 as a white solid (2.42 g, 65% yield).