Background and overview of synthesis and application examples of 4-chloro-2-methyl ester phenylboronic acid
4-Chloro-2-methoxybenzeneboronic acid is a very important chemical intermediate and is widely used in medicine and other fields. Boric acid compounds can undergo Suzuki reactions with chlorine, bromine or iodinated aromatics and alkenes, thereby connecting a variety of groups, and the downstream products are very rich.
Synthesis and application examples of 4-chloro-2-methyl ester phenylboronic acid
Synthesis and application examples of 4-chloro-2-methyl ester phenylboronic acid step 1, 4-chloro-2-methyl ester phenyl boronic acid pinacol ester
Methyl 2-bromo-5-chlorobenzoate (3.15 g, 12.63 mmol, 1 equivalent), pinacol diboronate (5.35 g, 13.89 mmol, 1.1 equivalent), Pd (dppf) Cl2·DCM (413 mg, 0.51 mmol, 4 mol%) and KOAc (3.72 g, 37.89 mmol, 3 equiv) were dissolved in 1,4-dioxane (80 mL) and degassed with N2. The reaction was heated to 90°C for 24 hours. The mixture was cooled to room temperature, filtered through a plug of silica gel, washed with EtOAc (50 mL), and the filtrate was evaporated. Purification of the residue by column chromatography (silica gel, 0-10% EtOAc in petroleum ether) afforded 4-chloro-2-methoxyphenylboronic acid pinacol ester (2.76 g, formylphenylboronic acid 74%) as a clear oil.
Synthesis and Application Examples of 4-Chloro-2-methoxycarbonylphenylboronic acid Step 2. Synthesis of (4-chloro-2-(methoxycarbonyl)phenyl)potassium trifluoroborate
Dissolve 4-chloro-2-methoxyphenylboronic acid pinacol ester (2.7 g, 9.10 mmol, 1 equiv) in MeOH (25 mL). Potassium hydrogen fluoride (4.5 M aqueous solution, 10.0 mL, 45.0 mmol, 5 equiv) was added and the resulting thick white slurry was stirred at room temperature for 30 minutes. The reaction mixture was then concentrated in vacuo. The residue was suspended in hot acetone and filtered. The filtrate was evaporated, and the residue was azeotroped 3 times with 1:1 MeOH:H2O (30 mL) to give (4-chloro-2-(methoxycarbonyl)phenyl)trifluoro Potassium borate (1.28g, 51%), as a white solid.
Synthesis and application examples of 4-chloro-2-methyl ester phenylboronic acid Step 3. Synthesis of 4-chloro-2-methyl ester phenyl boronic acid
Dissolve potassium (4-chloro-2-(methoxycarbonyl)phenyl)trifluoroborate (1.25 g, 4.52 mmol, 1 equiv) in MeCN (45 mL). H2O (0.24 mL, 13.56 mmol, 3 equiv) and TMSCl (1.72 mL, 13.56 mmol, 3 equiv) were added, and the reaction was stirred at room temperature for 1 h, then added with saturated NaHCO3 Quenched with aqueous solution (7 mL). The mixture was diluted with EtOAc (40 mL), the organics were separated and washed with water (2 × 20 mL), and the aqueous extract was extracted again with EtOAc (2 × 10 mL). The combined organics were dried over Na2SO4, filtered and concentrated to give the crude title compound (967 mg, 100%).
Synthesis and application examples of 4-chloro-2-methyl ester phenylboronic acid
4-Chloro-2-carboxyl phenylboronic acid can be used to prepare an electron transport material with the following structure to improve the working efficiency and extend the service life of organic electroluminescent devices. This type of compound has the parent structure of an asymmetrically substituted dibenzoheterocycle, has high bond energy between atoms, has good thermal stability, is conducive to solid-state stacking between molecules, and has strong electron transition ability. When used as an electron transport material, it has a suitable energy level between adjacent levels, which is conducive to the injection and migration of electrons, can effectively reduce the driving mica voltage, and has a high electron migration rate, which can be used in organic electroluminescence. Achieve good luminous efficiency in the device.
References
[1] Molloy J J , Law R P , Fyfe J W B , et al. A modular synthesis of functionalized phenols enabled by controlled boron speciation[J]. Organic & Biomolecular Chemistry, 2015, 13.
[2] [Chinese invention] CN202010905494.3 A compound, electron transport material and organic electroluminescent device
