Carbonyl alpha-carbon free radicals with high stability and preparation method thereof

Abstract

The invention discloses a class of carbonyl alpha-carbon free radicals with high stability and a preparation method, and relates to the field of organic free radical preparation, the structural general formula is R-CO-C.Ar1Ar2], Ar1 and Ar2 are aromatic hydrocarbons and heteroaromatic hydrocarbons containing halogen groups, methyl groups, trifluoromethyl groups, cyano groups and methoxyl groups, the carbonyl alpha-carbon free radicals with high stability are prepared under a protective atmosphere, and the carbonyl alpha-carbon free radicals with high stability are prepared by a one-step method. The method comprises the following steps: reacting diaryl carboxylic acid with one of an alkyl Grignard reagent, amine, alcohol, mercaptan and thiophenol according to a molar ratio of 1: (1-3) to obtain a free radical precursor, reacting the free radical precursor with alkali, losing one proton, then reacting the free radical precursor with a single-electron oxidant to lose one electron, and reacting the free radical precursor with the single-electron oxidant to obtain the diaryl carboxylic acid. The molar ratio of the free radical precursor to the alkali to the single-electron oxidant is 1: (1-4): (1-4), the carbonyl alpha-carbon free radical with high stability is obtained, and the carbonyl alpha-carbon free radical has good air stability and is not easy to decompose and deteriorate under natural light.

Description

Technical Field

[0001] This invention relates to the field of organic free radical preparation, specifically to a class of highly stable carbonyl α-carbon free radicals and their preparation method. Background Technology

[0002] With the significant improvement in the stability of organic free radicals, they have shown broad application prospects as open-shell organic photoelectric and electromagnetic functional molecules in many fields such as organic light-emitting diodes (OLEDs), energy storage electrolytes, spin labeling, and magnetic resonance imaging. Examples include common nitroxide free radicals such as TEMPO (2,2,6,6-tetramethylpiperidinyloxy), aminooxy, iminonitrooxide, nitroacylnitrooxide, and chlorotriarylmethyl free radicals. A rich variety of stable organic carbon, nitrogen, oxygen, and sulfur free radicals collectively constitute an open-shell organic molecular library.

[0003] Given the urgent need for a rich variety of open-shell organic molecules in optoelectronic applications, developing novel structures of stable organic radicals is crucial, especially for discovering organic radicals with unique properties and high photoelectric and thermal stability. Among the many types of stable organic radicals, carbonyl α-carbon radicals are an important class. In 2000, Professor JC Scaiano's team reported a radical with high antioxidant activity, HP-136, in *Organic Letters* (Org. Lett. 2000, 2, 899–901). Furthermore, Professor Chi Chunyan's team also developed carbonyl α-carbon radicals in the indoleone system (Angew. Chem. Int. Ed., 2024, 63, e202414533). However, the variety of carbonyl α-carbon radicals remains relatively limited. On the one hand, their structure is limited to special cyclic systems such as lactones and lactams; on the other hand, these radicals lack stability and are prone to dimerization in practical applications.

[0004] Given the above, developing highly stable carbonyl α-carbon radicals and expanding their variety is particularly urgent and significant. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a class of highly stable carbonyl α-carbon free radicals and a method for their preparation. By utilizing the high reactivity of the carbonyl group, a wide variety of stable carbonyl α-carbon free radical molecules can be prepared.

[0006] This invention is achieved through the following technical solution: A class of highly stable carbonyl α-carbon free radicals, the general structural formula of which is shown below: Where R is an aromatic hydrocarbon, heteroaromatic hydrocarbon, alkoxy group, amino group, phenoxy group, or mercapto group, the structural formulas of Ar1 and Ar2 are shown below: X1 and X2 are Cl, F, Br, OMe, CN, CF3 or Me, and Y1, Y2 and Y3 are H, F, Br, Cl, OMe, CN, CF3 or Me.

[0007] Preferably, the structural formula of the carbonyl α-carbon free radical is as follows:

[0008] .

[0009] A method for preparing a class of highly stable carbonyl α-carbon free radicals includes the following steps: Step 1: Under a protective atmosphere, diarylic acid carboxylic acid is reacted with one of aromatic hydrocarbons, heteroaromatic hydrocarbons, amines, alcohols, arylphenols, thiols, and thiophenols in a molar ratio of 1:(1~3) to obtain a free radical precursor. Step 2: The free radical precursor first reacts with a base, losing one proton, and then reacts with a single-electron oxidant, losing one electron. The molar ratio of the free radical precursor, base, and single-electron oxidant is 1:(1~4):(1~4), resulting in a highly stable carbonyl α-carbon free radical.

[0010] Preferably, when the diarylcarboxylic acid reacts with an aromatic hydrocarbon or heteroaromatic hydrocarbon, step 1 involves reacting the diarylcarboxylic acid with the aromatic hydrocarbon or heteroaromatic hydrocarbon, as well as trifluoromethanesulfonic acid, 2,2′,2″-((oxo-λ) 5 -phosphoryl)tri(oxy))trimethyltribenzoate is soluble in organic solvents, aromatic or heteroaromatic hydrocarbons, and trifluoromethanesulfonic acid and 2,2′,2″-((oxo-λ) 5 The molar ratio of trimethyl phosphotrimethyl(tri(oxy))tribenzoate was 2:0.2:1, and then the reaction was carried out at 0~110°C for 4-48h to obtain the free radical precursor. When a diarylcarboxylic acid reacts with an amine, alcohol, arylphenol, thiol, or thiophenol, step 1 involves dissolving the diarylcarboxylic acid, condensing agent, catalyst, amine, alcohol, arylphenol, thiol, or thiophenol in an organic solvent, and then reacting at 0–110°C for 4–48 h to obtain a free radical precursor.

[0011] Preferably, the molar ratio of the condensing agent and catalyst to the diaryl carboxylic acid is (1~3):0.4:1.

[0012] Preferably, the condensing agent is dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride or 1,1'-carbonyldiimidazole, and the catalyst is 4-dimethylaminopyridine, 1-hydroxybenzotriazole or 4-pyrrolidinylpyridine.

[0013] Preferably, the aromatic hydrocarbon in step 1 is benzene, trichlorobenzene or trimethylbenzene, the heteroaromatic hydrocarbon is pyridine, the amine is diethylamine, carbazole, dimethoxyaniline or morpholine, the alcohol is benzyl alcohol, phenol, naphthol or isopropanol, the thiophenol is p-methylthiophenol, and the thiol is isopropanethiol.

[0014] Preferably, in step 2, the free radical precursor is reacted with a base in an organic solvent at 25-40°C for 2-24 hours, followed by the addition of a single-electron oxidant, and the reaction is continued at room temperature for 4-48 hours to obtain a carbonyl α-carbon free radical with high stability.

[0015] Preferably, the alkali is one or more of sodium tert-butoxide, potassium tert-butoxide, sodium hydride, sodium hydroxide, pyridine, and triethylamine, and the single-electron oxidant is one or more of 2,3-dichloro-5,6-dicyanobenzoquinone, tetrachlorobenzoquinone, iodine, and potassium permanganate.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention constructs a class of highly stable carbonyl α-carbon free radicals. Ar1 and Ar2, representing aromatic and heteroaromatic hydrocarbons containing halogen, methoxy, and methoxy groups, provide steric protection for the highly reactive carbon-centered free radical. This strong steric protection prevents the free radical center from reacting with other molecules. Simultaneously, the electron-withdrawing effect of the carbonyl group ensures the free radical's stability. Furthermore, the carbonyl group can connect to various molecular fragments, including aromatic hydrocarbons, heteroaromatic hydrocarbons, alkoxy groups, amino groups, phenoxy groups, and mercapto groups. The carbonyl α-carbon free radicals of this invention are not easily decomposed or deteriorated in air or under natural light, exhibiting excellent stability and pioneering a novel organic carbon free radical system.

[0017] This invention provides a method for preparing a class of highly stable carbonyl α-carbon free radicals. Using readily available and inexpensive diarylcarboxylic acids as starting materials, the electron-withdrawing effect of the carbonyl group makes the carboxyl group highly reactive. It can react with aromatics or heteroaromatics using trifluoromethanesulfonic acid or phosphate esters, or with amines, alcohols, arylphenols, thiols, or thiophenols using condensing agents or catalysts, thereby synthesizing various carbonyl α-carbon free radical precursors. Multiple free radical precursors can be obtained through a one-step condensation reaction of carboxylic acids in air. The free radical precursor first reacts with a base to lose a proton, forming a negative ion. This negative ion reacts with a single-electron oxidant to lose an electron, leaving a single electron on the α-carbon atom adjacent to the carbonyl group, thus forming the product carbonyl α-carbon free radical. This product exhibits good air stability and is not easily decomposed or deteriorated under natural light. The preparation method of this invention is simple to operate, has good product yield, and can achieve gram-scale preparation, showing broad application prospects in the field of optoelectronic functional materials. Attached Figure Description

[0018] Figure 1 The hydrogen nuclear magnetic resonance spectrum of M-B1 prepared in Example 1 of this invention at 400 MHz ( 1 H NMR, CDCl3).

[0019] Figure 2 The hydrogen nuclear magnetic resonance spectrum of M-B2 prepared in Example 2 of this invention at 400 MHz ( 1 H NMR, CDCl3).

[0020] Figure 3 The hydrogen nuclear magnetic resonance spectrum of M-B3 prepared in Example 2 of this invention at 400 MHz ( 1 H NMR, CDCl3).

[0021] Figure 4 The hydrogen nuclear magnetic resonance spectrum of M-B4 prepared in Example 3 of this invention at 400 MHz ( 1 H NMR, CDCl3).

[0022] Figure 5 The hydrogen nuclear magnetic resonance spectrum of M-C1 prepared in Example 4 of this invention at 400 MHz ( 1 H NMR, CDCl3).

[0023] Figure 6 The hydrogen nuclear magnetic resonance spectrum of M-C2 prepared in Example 5 of this invention at 400 MHz ( 1 H NMR, CDCl3).

[0024] Figure 7 The hydrogen nuclear magnetic resonance spectrum of M-C3 prepared in Example 5 of this invention at 400 MHz (1 H NMR, CDCl3).

[0025] Figure 8 EPR images of M-B1, M-B3, M-B4, M-C1 and M-C4 prepared for embodiments of the present invention.

[0026] Figure 9 This is a molecular structure diagram of M-B4 as described in this invention.

[0027] Figure 10 This is a free radical crystal diagram of M-B4 described in this invention.

[0028] Figure 11 This is a molecular structure diagram of M-B1 described in this invention.

[0029] Figure 12 This is a free radical crystal diagram of M-B1 described in this invention.

[0030] Figure 13 This is a molecular structure diagram of M-C3 described in this invention.

[0031] Figure 14 This is a free radical crystal diagram of M-C3 described in this invention.

[0032] Figure 15 This is a stability test diagram of M-A2 prepared in Example 2 of the present invention under natural light conditions.

[0033] Figure 16 This is a fitting graph showing the decrease in absorbance over time of M-A2 prepared in Example 2 of the present invention under natural light conditions.

[0034] Figure 17 This is a stability test diagram of M-B3 prepared in Example 4 of the present invention under natural light conditions.

[0035] Figure 18 This is a fitting graph showing the decrease in absorbance over time of M-B3 prepared in Example 4 of the present invention under natural light conditions.

[0036] Figure 19 This is a stability test diagram of M-C2 prepared in Example 7 of the present invention under natural light conditions.

[0037] Figure 20 The figure shows the fitting graph of the absorbance of M-C2 prepared in Example 7 of the present invention decreasing over time under natural light conditions.

[0038] Figure 21 The cyclic voltammetry test diagram of M-B2 prepared in Example 4 of this invention is shown.

[0039] Figure 22 The cyclic voltammetry test diagram of M-C2 prepared in Example 7 of this invention is shown.

[0040] Figure 23 UV-Vis absorption spectra of n-hexane solutions (0.1 nM) of M-A1, M-A3, M-B2, M-C1, M-C3 and M-D1 prepared for embodiments of the present invention. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific implementation examples. It should be understood that the present invention is not limited to the following embodiments, and the following embodiments are only illustrative implementations of the present invention.

[0042] The novel carbonyl α-carbon free radical compounds involved in this invention refer to a class of organic compounds in which the carbon free radical center is connected to a carbonyl group in the molecular structure, and is also connected to two aromatic or heteroaromatic hydrocarbons. The specific structural formula of these compounds can be represented as M [R-CO-C·Ar1Ar2], where R, Ar1, and Ar2 represent different substituents. The specific range of substituents can be further explained. For example, R can be aryl, heteroaromatic, alkoxy, amino, phenoxy, or mercapto, and Ar1 and Ar2 are aromatic hydrocarbons containing substituents or heteroaromatic hydrocarbons containing substituents.

[0043] This invention relates to a class of compounds with carbonyl α-carbon free radicals, characterized by a central carbon free radical linked to two aromatic hydrocarbons and a carbonyl group, with the following general chemical structural formula:

[0044] The MA structure can be further expressed as follows:

[0045] The MB structure can be further expressed as follows:

[0046] The MC structure can be further expressed as follows:

[0047] The MD structure can be further expressed as follows:

[0048] The present invention discloses a method for preparing a class of compounds containing carbonyl α-carbon free radicals, specifically comprising the following steps: Step 1: Under a nitrogen atmosphere, diarylcarboxylic acids are dissolved in organic solvent A1 with aromatic hydrocarbons, heteroaromatic hydrocarbons, amines, alcohols, arylphenols, thiols, or thiophenols of different structures to obtain a first mixture. Since aromatic hydrocarbons and heteroaromatic hydrocarbons have low reactivity, trifluoromethanesulfonic acid and 2,2′,2″-((oxo-λ) are added. 5-phosphoryl)tri(oxy))trimethyltribenzoate reacts with aromatic or heteroaromatic hydrocarbons with trifluoromethanesulfonic acid and 2,2′,2″-((oxo-λ) 5 The molar ratio of trimethyl phosphotrimethyl(tri(oxy))tribenzoate is 2:0.2:1. When amines, alcohols, arylphenols, thiols, or thiophenols are added, condensing agents and catalysts are required, and the reaction is carried out according to the following formula. Alternatively, the condensing agent and catalyst can be added together. The reaction temperature is 0°C to 110°C, and the reaction time is 4 to 48 hours. At the above temperatures, it can spontaneously react with diarylcarboxylic acids. The diarylcarboxylic acid and the condensing agent first form a highly active O-acylisourea intermediate. This intermediate further reacts with the catalyst to form an acylpyridinium salt. Finally, the acylpyridinium salt condenses with the substrate amine, alcohol, arylphenol, thiol, or thiophenol to form the final product. The reaction is monitored by thin-layer chromatography (TLC) or nuclear magnetic resonance (NMR). When the diarylcarboxylic acid is completely consumed, water or hydrochloric acid is added to terminate the reaction, and dichloromethane is added for extraction. The organic phases are combined, and the solvent is removed under reduced pressure. After separation and purification by column chromatography, different free radical precursors are obtained.

[0049]

[0050] 2,2′,2″-((Oxyto-λ) 5 The structural formula of trimethyl phosphotrimethyl(tri(oxy))tribenzoate is as follows:

[0051] The molar ratio of diarylcarboxylic acid, (aromatic hydrocarbons, heteroaromatic hydrocarbons, amines, alcohols, arylphenols, thiols or thiophenols), condensing agent and catalyst is 1:(1~3):(1~3):0.4. The concentration of diarylcarboxylic acid in the first mixture or mixed system is 0.1M (0.1mol / L).

[0052] Aromatic hydrocarbons are selected from benzene, trimethylbenzene, and trichlorobenzene; heteroaromatic hydrocarbons are selected from pyridine. Amines are selected from diethylamine, carbazole, dimethoxyaniline, or morpholine. Alcohols are selected from benzyl alcohol, phenol, naphthol, or isopropanol. Thiophenols are selected from p-methylthiophenol, and thiols are selected from isopropanethiol. Organic solvent A1 is selected from one or more of dichloromethane, cyclohexane, ethyl acetate, toluene, 1,2-dichloroethane, and tetrahydrofuran in any proportion.

[0053] The condensing agent is selected from DCC (dicyclohexylcarbodiimide), DIC (diisopropylcarbodiimide), EDCI (1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride), and CDI (1,1'-carbonyldiimidazole).

[0054] The catalysts were selected from DMAP (4-dimethylaminopyridine), HOBt (1-hydroxybenzotriazole), and 4-PPY (4-pyrrolidinylpyridine).

[0055] Step 2: Dissolve the free radical precursor obtained in Step 1 with an alkali in organic solvent A2 to obtain a second mixture. React at 25°C-40°C for 2-24 hours. Then add a single-electron oxidant and continue the reaction at room temperature for 4-48 hours. Monitor with TLC or NMR. Stop the reaction after the organic free radical precursor is completely consumed. After separation and purification, free radicals M-A1 to A4, M-B1 to B4, M-C1 to C4, and M-D1 to D2 are obtained.

[0056]

[0057] The molar ratio of the free radical precursor, base, and single-electron oxidant is 1:(1~4):(1~4). The concentration of the free radical precursor in the second mixture is 0.1M (0.1mol / L).

[0058] The base is selected from one or more of sodium tert-butoxide, potassium tert-butoxide, sodium hydride, sodium hydroxide, pyridine, and triethylamine in any proportion. The organic solvent A2 is selected from one or more of toluene, dichloromethane, tetrahydrofuran (THF), 1,4-dioxane, diethyl ether, and ethyl acetate in any proportion. The single-electron oxidant is selected from one or more of DDQ (2,3-dichloro-5,6-dicyanobenzoquinone), tetrachlorobenzoquinone, iodine, and potassium permanganate in any proportion.

[0059] Example 1 Synthesis of compound M-A1

[0060] Step 1: Under a nitrogen atmosphere, compound 1 (41.6 mg, 0.1 mmol, 1 eq), 1-1 (benzene 0.2 mmol, 2 eq), trifluoromethanesulfonic acid (0.02 mmol, 0.2 eq), 2,2′,2″-((oxo-λ) 5 Trimethyl phosphotrimethyl(phosphotrimethyl)tri(oxy)tribenzoate (abbreviated as PO(osalMe)3, 0.1 mmol, 1 eq) was dissolved in 2 mL of tetrahydrofuran and reacted at 0°C for 4 hours. After complete conversion by TLC, 10 mL of water was added, followed by extraction with dichloromethane. The organic phases were combined, and the solvent was removed under reduced pressure. The residue was then separated by column chromatography to give products 1-2, white solids, with a yield of 78%.

[0061] Step 2: Dissolve 1-2 (47.6 mg, 0.1 mmol, 1 eq) and NaH (6 mg, 0.2 mmol, 2 eq) in 2 mL of dry THF and react at 40°C for 4 hours. Then add DDQ (45.4 mg, 0.2 mmol, 2 eq) and continue the reaction at room temperature for 12 hours. After the organic free radical precursor is completely consumed, stop the reaction, remove the solvent under reduced pressure, and separate the residue by column chromatography to obtain compound M-A1, a dark red solid, with a yield of 74%.

[0062] Example 2 The synthetic methods used for compounds M-A2, M-A3, and M-A4 are the same as those used for M-B1, except that substrate 1-1 is replaced with trimethylbenzene, trichlorobenzene, and pyridine in sequence.

[0063]

[0064] Example 3 Synthesis of compound M-B1

[0065] Step 1: Under a nitrogen atmosphere, compound 1 (41.6 mg, 0.1 mmol, 1 eq), 2 (morpholine, 17.4 mg, 0.2 mmol, 2 eq), DCC (41.3 mg, 0.2 mmol, 2 eq), and DMAP (5 mg, 0.04 mmol, 0.4 eq) were dissolved in 2 mL of toluene. The reaction was carried out at room temperature for 24 hours. After complete conversion of compound 1 by TLC, 10 mL of 2M dilute hydrochloric acid was added, followed by extraction with dichloromethane. The organic phases were combined, and the solvent was removed under reduced pressure. The residue was then separated by column chromatography to obtain product 3, a white solid with a yield of 88%.

[0066] Step 2: Dissolve 3 (48.4 mg, 0.1 mmol, 1 eq) and NaH (6 mg, 0.2 mmol, 2 eq) in 2 mL of dry THF and react at 40°C for 4 hours. Then add DDQ (45.4 mg, 0.2 mmol, 2 eq) and continue the reaction at room temperature for 12 hours. After the organic free radical precursor is completely consumed, stop the reaction, remove the solvent under reduced pressure, and separate the residue by column chromatography to obtain compound M-B1, a dark red solid, with a yield of 92%.

[0067] Example 4 The synthetic methods used for compounds M-B2 and M-B3 are the same as those for M-B1, except that substrate 2 is replaced with diethylamine and diphenylamine. ;

[0068] M-B2M-B3.

[0069] Example 5 Synthesis of compound M-B4

[0070] Step 1: Under a nitrogen atmosphere, compound 1 (41.6 mg, 0.1 mmol, 1 eq), carbazole (33.4 mg, 0.2 mmol, 2 eq), DCC (41.3 mg, 0.2 mmol, 2 eq), and DMAP (5 mg, 0.04 mmol, 0.4 eq) were dissolved in 2 mL of tetrahydrofuran. The reaction was carried out at room temperature for 24 hours. When compound 1 was completely consumed by TLC, 10 mL of water was added, followed by extraction with dichloromethane. The organic phases were combined, and the solvent was removed under reduced pressure. The residue was then separated by column chromatography to obtain product 5, a white solid with a yield of 37%.

[0071] Step 2: Dissolve 5 (56.5 mg, 0.1 mmol, 1 eq) and NaH (6 mg, 0.2 mmol, 2 eq) in 2 mL of dry THF and react at 40°C for 4 hours. Then add DDQ (45.4 mg, 0.2 mmol, 2 eq) and continue the reaction at room temperature for 12 hours. After the organic free radical precursor is completely consumed, stop the reaction, remove the solvent under reduced pressure, and separate the residue by column chromatography to obtain compound M-B4, a pale purple solid, with a yield of 88%.

[0072] Example 6 Synthesis of compound M-C1

[0073] Step 1: Under a nitrogen atmosphere, compounds 1 (14.6 mg, 0.1 mmol, 1 eq), 6 (12.0 mg, 0.2 mmol, 2 eq), DCC (41.3 mg, 0.2 mmol, 2 eq), and DMAP (5 mg, 0.04 mmol, 0.4 eq) were dissolved in 2 mL of toluene. The reaction was carried out at room temperature for 24 hours. After complete conversion of compound 1 by TLC, 10 mL of water was added, followed by extraction with dichloromethane. The organic phases were combined, and the solvent was removed under reduced pressure. The residue was then separated by column chromatography to obtain product 7, a white solid with a yield of 67%.

[0074] Step 2: Compound 7 (45.8 mg, 0.1 mmol, 1 eq) and NaH (8 mg, 0.2 mmol, 2 eq) were dissolved in 2 mL of dry THF and reacted at 40°C for 4 hours. Then DDQ (45.4 mg, 0.2 mmol, 2 eq) was added, and the reaction was continued at room temperature for 12 hours. After the organic free radical precursor was completely consumed, the reaction was stopped. The solvent was removed under reduced pressure, and the residue was separated by column chromatography to give compound M-Cl, a dark red solid, with a yield of 84%.

[0075] Example 7 The synthetic methods used for compounds M-C2 and M-C3 are the same as those used for M-C1, except that substrate 6 is replaced with benzyl alcohol and phenol. ;

[0076] M-C2M-C3.

[0077] Example 8 Synthesis of compound M-D2

[0078] Step 1: Under a nitrogen atmosphere, compounds 1 (43.4 mg, 0.1 mmol, 1 eq), 8 (24.8 mg, 0.2 mmol, 2 eq), DCC (41.3 mg, 0.2 mmol, 2 eq), and DMAP (5 mg, 0.04 mmol, 0.4 eq) were dissolved in 2 mL of toluene. The reaction was carried out at room temperature for 24 hours. After complete conversion of compound 1 by TLC, 10 mL of water was added, followed by extraction with dichloromethane. The organic phases were combined, and the solvent was removed under reduced pressure. The residue was then separated by column chromatography to obtain product 9, a white solid with a yield of 86%.

[0079] Step 2: Compound 9 (45.8 mg, 0.1 mmol, 1 eq) and NaH (8 mg, 0.2 mmol, 2 eq) were dissolved in 2 mL of dry THF and reacted at 40°C for 4 hours. Then DDQ (45.4 mg, 0.2 mmol, 2 eq) was added, and the reaction was continued at room temperature for 12 hours. After the organic free radical precursor was completely consumed, the reaction was stopped. The solvent was removed under reduced pressure, and the residue was separated by column chromatography to give compound M-D2, a dark red solid, with a yield of 86%.

[0080] Example 9 The synthesis method used for compound M-D1 is the same as that used for M-D2, except that substrate 8 is replaced with isopropylthiophenol.

[0081] Although the invention has been described with reference to examples, it is not limited to the embodiments described above. It should be understood that, guided by the inventive concept, those skilled in the art can make various modifications and improvements, and apply the general principles described herein to other examples without inventive effort. Therefore, the invention is not limited to the embodiments described above, and any improvements and modifications made by those skilled in the art based on the description, without departing from the scope of the invention, should be within the protection scope of the invention.

[0082] from Figure 1 As can be seen from the 1H NMR spectrum, the number of hydrogen atoms and the splitting pattern are consistent with the structure of the target compound. Therefore, the target product M-B1 was obtained by this method.

[0083] from Figure 2 As can be seen from the 1H NMR spectrum, the number of hydrogen atoms and the splitting pattern are consistent with the structure of the target compound. Therefore, the target product M-B2 was obtained by this method.

[0084] from Figure 3 As can be seen from the 1H NMR spectrum, the number of hydrogen atoms and the splitting pattern are consistent with the structure of the target compound. Therefore, the target product M-B3 was obtained by this method.

[0085] from Figure 4 As can be seen from the 1H NMR spectrum, the number of hydrogen atoms and the splitting pattern are consistent with the structure of the target compound. Therefore, the target product M-B4 was obtained by this method.

[0086] from Figure 5 As can be seen from the hydrogen NMR spectrum, the number of hydrogen atoms and the splitting are consistent with the structure of the target compound. Therefore, the target product M-C1 was obtained by this method.

[0087] from Figure 6 As can be seen from the 1H NMR spectrum, the number of hydrogen atoms and the splitting pattern are consistent with the structure of the target compound. Therefore, the target product M-C3 was obtained by this method.

[0088] from Figure 7 As can be seen from the 1H NMR spectrum, the number of hydrogen atoms and the splitting pattern are consistent with the structure of the target compound. Therefore, the target product M-C4 was obtained by this method.

[0089] from Figure 8 As can be seen from the EPR test, compounds M-B1, M-B3, M-B4, M-C1, and M-C4 have obvious spectral signals, thus a carbon radical center was successfully generated by the above method.

[0090] Figure 9 This is the molecular structure diagram of M-B4. Figure 10The free radical crystal diagram of M-B4 matches its molecular structure diagram, thus confirming the discovery of the target free radical.

[0091] Figure 11 This is the molecular structure diagram of M-B1. Figure 12 The free radical crystal diagram of M-B1 matches its molecular structure diagram, thus confirming the discovery of the target free radical.

[0092] Figure 13 This is a free radical crystal diagram of M-C3. Figure 14 The free radical crystal diagram of M-C3 matches its molecular structure diagram, thus confirming the discovery of the target free radical.

[0093] The free radicals described in this invention exhibit excellent stability, as illustrated in the following figures, which demonstrate their stability under natural light: Figure 15 This is a graph showing the decrease in absorbance over time of a 0.1 nM hexane solution of M-A2 under natural light conditions. Figure 16 It is based on Figure 15 The obtained fitted graph shows the absorbance decay over time, where the coefficient of determination R of the fitted line is... 2 = 0.98429. It is generally believed that the decay of a compound is a first-order kinetic process, and its half-life calculation conforms to the first-order kinetic half-life formula:

[0094] Based on the fitted line and the formula, the stability of the M-A2 n-hexane solution (0.1 nM) under natural light conditions can reach approximately 342 h. This indicates that the free radical is not easily decomposed or deteriorated under natural light irradiation and can be stored for a long time under natural conditions.

[0095] Figure 17 This is a graph showing the decrease in absorbance over time of a hexane solution (0.1 nM) of compound M-B3 under natural light conditions.

[0096] Figure 18 It is based on Figure 17 The obtained fitted graph shows the absorbance decay over time, where the coefficient of determination R of the fitted line is... 2 = 0.97741. Based on the fitted line and the above formula, the stability of the hexane solution (0.1 nM) of M-B3 under natural light conditions can reach about 935 h, indicating that the free radical is not easily decomposed or deteriorated under natural light irradiation and can be stored for a long time under natural conditions. Figure 19 This is a graph showing the decrease in absorbance over time of a 0.1 nM hexane solution of compound C2 under natural light conditions.

[0097] Figure 20It is based on Figure 19 The obtained fitted graph shows the absorbance decay over time, where the coefficient of determination R of the fitted line is... 2 = 0.99077. Based on the fitted line and the above formula, the stability of the M-C2 n-hexane solution (0.1 nM) under natural light conditions can reach about 77 h, indicating that the free radical is not easily decomposed or deteriorated under natural light irradiation and can be stored for a long time under natural conditions.

[0098] Cyclic voltammetry test of M-B2, such as Figure 21 As shown, Figure 21 No significant decomposition was observed after 50 cycles of M-B2.

[0099] Cyclic voltammetry test of M-C2, such as Figure 22 As shown, Figure 22 No significant decomposition was observed after 50 cycles of the M-C2.

[0100] from Figure 23 It can be seen that the free radicals M-A1, M-A3, M-B2, M-C1, M-C3 and M-D1 have a characteristic absorption peak between 520nm and 550nm, indicating that this type of compound contains a characteristic free radical center.

Claims

1. A class of highly stable carbonyl α-carbon free radicals, characterized in that, The general structural formula of the carbonyl α-carbon free radical is shown below: Where R is an aromatic hydrocarbon, heteroaromatic hydrocarbon, alkoxy group, amino group, phenoxy group, or mercapto group, the structural formulas of Ar1 and Ar2 are shown below: X1 and X2 are Cl, F, Br, OMe, CN, CF3 or Me, and Y1, Y2 and Y3 are H, F, Br, Cl, OMe or Me, CN, CF3.

2. The carbonyl α-carbon free radical with high stability according to claim 1, characterized in that, The structural formula of the carbonyl α-carbon free radical is as follows: 。 3. The method for preparing a type of highly stable carbonyl α-carbon free radical as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1, under a protective atmosphere, diarylic acid carboxylic acid is reacted with one of aromatic hydrocarbons, heteroaromatic hydrocarbons, amines, alcohols, arylphenols, thiols and thiophenols in a molar ratio of 1:(1~3) to obtain a free radical precursor. S2, the free radical precursor first reacts with the base, losing one proton, and then reacts with the single-electron oxidant, losing one electron. The molar ratio of the free radical precursor, the base and the single-electron oxidant is 1:(1~4):(1~4), resulting in a highly stable carbonyl α-carbon free radical.

4. The method for preparing a type of highly stable carbonyl α-carbon free radical according to claim 3, characterized in that, When diarylcarboxylic acids react with aromatic or heteroaromatic hydrocarbons, S1 reacts the diarylcarboxylic acids with aromatic or heteroaromatic hydrocarbons, as well as trifluoromethanesulfonic acid, 2,2′,2″-((oxo-λ) 5 -phosphoryl)tri(oxy))trimethyltribenzoate is soluble in organic solvents, aromatic or heteroaromatic hydrocarbons, and trifluoromethanesulfonic acid and 2,2′,2″-((oxo-λ) 5 The molar ratio of trimethyl phosphotrimethyl(tri(oxy))tribenzoate was 2:0.2:1, and then the reaction was carried out at 0~110°C for 4-48h to obtain the free radical precursor. When a diarylcarboxylic acid reacts with an amine, alcohol, arylphenol, thiol, or thiophenol, S1 dissolves the diarylcarboxylic acid, condensing agent, catalyst, and amine, alcohol, arylphenol, thiol, or thiophenol in an organic solvent, and then reacts at 0-110°C for 4-48 hours to obtain a free radical precursor.

5. The method for preparing a type of highly stable carbonyl α-carbon free radical according to claim 4, characterized in that, The organic solvent is one or more selected from dichloromethane, cyclohexane, ethyl acetate, toluene, 1,2-dichloroethane, and tetrahydrofuran.

6. The method for preparing a type of highly stable carbonyl α-carbon free radical according to claim 4, characterized in that, The molar ratio of the condensing agent and catalyst to the diaryl carboxylic acid is (1~3): 0.4:

1.

7. The method for preparing a type of highly stable carbonyl α-carbon free radical according to claim 4, characterized in that, The condensing agent is dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride or 1,1'-carbonyldiimidazole, and the catalyst is 4-dimethylaminopyridine, 1-hydroxybenzotriazole or 4-pyrrolidinylpyridine.

8. The method for preparing a type of highly stable carbonyl α-carbon free radical according to claim 3, characterized in that, The aromatic hydrocarbons described in S1 are benzene, trichlorobenzene, or trimethylbenzene; the heteroaromatic hydrocarbons are pyridine; the amines are diethylamine, carbazole, dimethoxyaniline, or morpholine; the alcohols are benzyl alcohol, phenol, naphthol, or isopropanol; the thiophenols are p-methylthiophenol; and the thiols are isopropanethiol.

9. The method for preparing a type of highly stable carbonyl α-carbon free radical according to claim 3, characterized in that, S2 reacts the radical precursor with a base in an organic solvent at 25-40°C for 2-24 hours, then adds a single-electron oxidant and continues the reaction at room temperature for 4-48 hours to obtain a highly stable carbonyl α-carbon radical.

10. The method for preparing a type of highly stable carbonyl α-carbon free radical according to claim 9, characterized in that, The base is one or more of sodium tert-butoxide, potassium tert-butoxide, sodium hydride, sodium hydroxide, pyridine, and triethylamine, and the single-electron oxidant is one or more of 2,3-dichloro-5,6-dicyanobenzoquinone, tetrachlorobenzoquinone, iodine, and potassium permanganate.

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