Synthesis of 2-substituted tetraphenylenes via transition-metal-catalyzed derivatization of tetraphenylene

A new strategy for the synthesis of 2-substituted tetraphenylenes through a transition-metal-catalyzed derivatization has been developed. Three types of functionalities, including OAc, X (Cl, Br, I) and carbonyl, were introduced onto tetraphenylene, which allows the easy access to a variety of monosubstituted tetraphenylenes. These reactions could accelerate research on the properties and application of tetraphenylene derivatives.

I. General procedure for screening of reaction conditions 1. Pd(OAc) 2 -catalyzed acetoxylation of tetraphenylene with PhI(OAc) 2 1 A 25 mL pressure resistant vial equipped with a magnetic stirring bar was charged with Pd(OAc) 2 (4.48 mg, 0.02 mmol), followed by pyridine (1.45 µL, 0.018 mmol), PhI(OAc) 2 and solvent. The resulting suspension was stirred at room temperature for 1 min, and then tetraphenylene (1,30.4 mg, 0.1 mmol) was added. The vial was sealed with a Teflon-lined cap, and the reaction mixture was heated to the inidacted temperature using a preheated hotplate. After the reaction mixture was stirred for the indicated time, it was allowed to cool to ambient temperature. The reaction mixture was diluted with ethyl acetate and then filtered through a small pad of Celite. The filtrate was concentrated in vacuo. The yield was determined by 1 H NMR analysis of crude product using CH 2 Br 2 as the internal standard.

AuCl 3 -catalyzed chlorination of tetraphenylene with NCS 2
A 25 mL pressure resistant vial equipped with a magnetic stirring bar was charged with tetraphenylene (1, 30.4 mg, 0.10 mmol), followed by AuCl 3 (1.5 mg, 0.005 mmol), NCS and DCE (1 mL). The resulting suspension was stirred at room temperature for 1 min, and then the additive was added. After the resulting reaction mixture was allowed to stir for the indicated time at the indicated temperature, it was allowed to cool to ambient temperature. The reaction mixture was diluted with ethyl acetate and then filtered through a small pad of Celite. The filtrate was concentrated in vacuo. The yield was determined by 1 H NMR analysis of crude product using CH 2 Br 2 as the internal standard.

AuCl 3 -catalyzed bromination of tetraphenylene with NBS 2
A 25 mL pressure resistant vial equipped with a magnetic stirring bar was charged with tetraphenylene (1, 30.4 mg, 0.10 mmol), followed by AuCl 3 (1.5 mg, 0.005 mmol), NBS and DCE (1 mL). After the resulting reaction mixture was allowed to stir for the indicated time at the indicated temperature it was allowed to cool to ambient temperature. The reaction mixture was diluted with ethyl acetate and then filtered through a small pad of Celite. The filtrate was concentrated in vacuo. The yield was determined by 1 H NMR analysis of crude product using CH 2 Br 2 as the internal standard.

AuCl 3 -catalyzed iodination of tetraphenylene with NIS 2
A 25 mL pressure resistant vial equipped with a magnetic stirring bar was charged with tetraphenylene (1, 30.4 mg, 0.10 mmol), followed by AuCl 3 (1.5 mg, 0.005 mmol), NIS and DCE (1 mL). After the resulting reaction mixture was allowed to stir for the indicated time at the indicated temperature, it was allowed to cool to ambient temperature. The reaction mixture was diluted with ethyl acetate and then filtered through a small pad of Celite. The filtrate was concentrated in vacuo. The yield was determined by 1 H NMR analysis of crude product using CH 2 Br 2 as the internal standard.

Pd(OAc) 2 -catalyzed carbonylation of tetraphenylene with nitriles 3
A 25 mL pressure resistant vial equipped with a magnetic stirring bar was charged with tetraphenylene (1, 30.4 mg, 0.10 mmol), followed by Pd(OAc) 2 , PhCN, DMSO, additive and trifluoroacetic acid (1 mL). The vial was sealed with a Teflon-lined cap, and the resulting reaction mixture was allowed to stir for 12 h at 100 °C. After cooling to room temperature, water (5 mL) was added to the mixture and the resulting mixture was heated at 120 °C for 2 h. After cooling to room temperature, the reaction mixture was diluted with ethyl acetate (20 mL), and then filtered through a pad of Celite. The filtrate was washed with brine (10 mL), dried over Na 2 SO 4 , and concentrated in vacuo. The yield was determined by 1 H NMR analysis of crude product using CH 2 Br 2 as the internal standard.

Synthesis of 2-acetoxytetraphenylene
A solution of PhI(OAc) 2 (96.6 mg, 0.30 mmol), Pd(OAc) 2 (4.5 mg, 0.02 mmol), pyridine (1.4 µL, 0.018 mmol) and Ac 2 O (0.05 mL) in AcOH (0.45 mL) was stirred at for 1min at room temperature. Then tetraphenylene (1, 30.4 mg, 0.10 mmol) was added and the reaction mixture was stirred for 12 h at 100 °C. At the end of the reaction, the solution was diluted with ethyl acetate (10 mL) and then filtered through a pad of Celite. The filtrate was concentrated in vacuo and the crude product was purified by preparative silica gel chromatography (eluent: petroleum ether/EtOAc 10:1).

Synthesis of 2-chlorotetraphenylene
A solution of tetraphenylene (1, 30.4 mg, 0.10 mmol), NCS (26.7 mg, 0.20 mmol) and AuCl 3 (1.5 mg, 0.005 mmol) in DCE (1 mL) was stirred at room temperature for 1 min, and then BF 3 ·Et 2 O (4.9 µL, 0.04 mmol) was added. The resulting reaction mixture was allowed to stir at 80 °C for 24 h. At the end of the reaction, the solution was diluted with ethyl acetate (10 mL) and then filtered through a pad of Celite. The filtrate was concentrated in vacuo and the crude product was purified by preparative silica gel chromatography (eluent: petroleum ether).

Synthesis of 2-bromotetraphenylene
A solution of tetraphenylene (1, 30.4 mg, 0.10 mmol), NBS (26.7 mg, 0.15 mmol) and AuCl 3 (1.5 mg, 0.005 mmol) in DCE (1 mL) was stirred at 80 °C for 24 h. At the end of the reaction, the solution was diluted with ethyl acetate (10 mL) and then filtered through a pad of Celite. The filtrate was concentrated in vacuo and the crude product was purified by preparative silica gel chromatography (eluent: petroleum ether).

Synthesis of 2-iodotetraphenylene
A solution of compound 1 (30.4 mg, 0.10 mmol), NIS (45.0 mg, 0.20 mmol) and AuCl 3 (1.5 mg, 0.005 mmol) in DCE (1 mL) was stirred at 60 °C for 12 h. At the end of the reaction, the solution was diluted with ethyl acetate (10 mL) and then filtered through a pad of Celite. The filtrate was concentrated in vacuo and the crude product was purified by preparative silica gel chromatography (eluent: petroleum ether).

Synthesis of 2-carbonyltetraphenylenes
A 25 mL pressure resistant vial equipped with a magnetic stir bar was charged with tetraphenylene (1, 30.4 mg, 0.10 mmol), followed by Pd(OAc) 2 (4.5 mg, 0.02 mmol), DMSO (14.2 µL, 0.2 mmol), RCN (0.25 mmol), DCM (0.2 mL) and trifluoroacetic acid (1 mL). The vial was sealed with a Teflon-lined cap, and the resulting reaction mixture was allowed to stir for 12 h at 100 °C. After cooling to room temperature, water (5 mL) was added to the mixture and the resulting mixture was heated at 120 °C for 2 h. After cooling to room temperature, the reaction mixture was diluted with ethyl acetate (20 mL), and then filtered through a pad of Celite. The filtrate was washed with brine (10 mL), dried over Na 2 SO 4 , and concentrated in vacuo. The crude product was purified by preparative silica gel chromatography (eluent: petroleum ether/EtOAc 10:1).