Synthesis and Amination Reaction of 9,10-Dibromoanthracene

9,10-Dibromoanthracene is an aromatic brominated compound that appears as a yellow solid powder under ambient temperature and pressure, exhibiting notable fluorescent properties. It is insoluble in water but soluble in common organic solvents such as ethyl acetate and dichloromethane. 9,10-Dibromoanthracene can be prepared by bromination of anthracene using suitable brominating agents, for instance, liquid bromine. This compound is primarily employed as a synthetic precursor for organic light-emitting materials.

Synthesis

Researchers have disclosed a preparation method for 9,10-dibromoanthracene using bromodimethylsulfonium bromide (BDMS) as the brominating agent. This method employs dichloromethane, chloroform, or carbon tetrachloride as the solvent. After the reaction is completed, 9,10-dibromoanthracene is obtained via suction filtration with high yield and purity. The reported synthesis of 9,10-dibromoanthracene is characterized by its environmentally friendly brominating reagent, simple operational procedure, and short reaction time. The synthetic method is carried out in a reaction system containing an organic solvent, wherein bromination occurs at the 9- and 10- positions of anthracene using BDMS as the brominating agent to produce 9,10-dibromoanthracene. The organic solvent is selected from dichloroethane, chloroform, or carbon tetrachloride; the molar ratio of anthracene to BDMS is 1:1–2; the reaction temperature ranges from 0 to 50°C, and the reaction time is 30–60 minutes. [1]

Photochemical Properties

The photochemical behavior of 9,10-Dibromoanthracene was investigated using a two‑laser two‑color technique in benzene and cyclohexane. In benzene solution, excitation of the triplet state with a dye laser (467 nm) led to triplet‑state bleaching with a quantum yield of 0.041. The upper triplets decay via a combination of processes, including reverse intersystem crossing (Φ = 0.09), resulting in dye‑laser‑induced fluorescence from the S₁ state. Additionally, about 4 % of the re‑excited triplets underwent debromination. The lifetimes of the upper triplets of 9,10-Dibromoanthracene were estimated to be approximately 200 ps for T₂ and ~20 ps for Tₙ (n > 2). The quantum yield for reverse intersystem crossing was higher in cyclohexane (0.17) than in benzene (0.09); this difference likely reflects quenching of the upper triplets (Tₙ, n > 2) by the benzene solvent. [2]

Amination Reaction

图1 Amination Reaction of 9,10-Dibromoanthracene

In a 250 mL two-necked round-bottom flask, a mixture of 9,10-Dibromoanthracene (1.31 g, 3.9 mmol), diphenylamine (1.68 g, 9.77 mmol), and sodium tert‑butoxide (2.72 g, 19.5 mmol) is charged, followed by the addition of anhydrous toluene (60 mL). The reaction vessel is then subjected to three consecutive evacuation/argon backfill cycles to thoroughly remove atmospheric oxygen and establish an inert argon atmosphere. Tris(dibenzylideneacetone)dipalladium(0) (0.11 g, 0.12 mmol) and tri‑tert‑butylphosphine (0.15 mL, 0.35 mmol) are added, and the mixture is gradually warmed to 50°C and held at this temperature for 0.5 h. The temperature is then raised to 110°C, and the reaction is refluxed under argon for 48 h. After completion, the mixture is concentrated under reduced pressure, and the organic phase is extracted with water and methylene chloride several times. The crude product is obtained by rotary evaporation to remove the solvent. [3]

Application

Using bis(diphenylphosphino)ferrocene palladium(II) dichloride (PdCl₂(dppf)) as the catalyst, 9,10-dibromoanthracene and α-naphthaleneboronic acid as starting materials, the blue-light-emitting material 9,10-di(α-naphthyl)anthracene was synthesized via the Suzuki coupling reaction. The effects of reaction conditions—such as catalyst loading, solvent, base, reaction temperature, and the molar ratio of α-naphthaleneboronic acid to 9,10-dibromoanthracene—on the yield were investigated. The optimal conditions were determined as follows: a toluene/ethanol/water system (volume ratio 6/1/2); a molar ratio of α-naphthaleneboronic acid to 9,10-dibromoanthracene of 3:1; catalyst loading at 0.5 mol% relative to the halogenated arene; potassium carbonate as the base; and a reaction time of 7 hours, achieving a yield of 98%. This result is significantly superior to that obtained with the commonly used tetrakis(triphenylphosphine)palladium(0) (Pd(PPh₃)₄) catalyst. After purification by recrystallization, the product purity exceeded 99%, making it directly applicable in OLED devices. [4]

Reference

[1] J. Liu et al., A preparation method of 9,10-dibromoanthracene: CN 201310049884 [P]. (in Chinese)

[2] W. G. McGimpsey, J. C. Scaiano, Photochemistry and photophysics from upper triplet levels of 9,10?dibromoanthracene, J. Am. Chem. Soc., 1989, 111, 335–340.

[3] J. Luo et al., A novel anthracene?scaffolded triazine?based porous organic polymer for efficient capture of iodine in gaseous and liquid phases, Microporous Mesoporous Mater., 2026, 399, 113836.

[4] Y. Wang, X. Bai, H. Lü, Synthesis of blue?light?emitting material 9,10?di(α?naphthyl)anthracene, Chem. Adhes., 2010, (6), 30–32.

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