Phenolic compound with caramel sweet fragrance, preparation method of phenolic compound and caramel sweet guaiaucklandia base

Abstract

The invention relates to the technical field of flavors and fragrances, in particular to a phenolic compound with caramel sweet fragrance, a preparation method of the phenolic compound and a caramel sweet guaiaki base. The phenolic compound with the caramel sweet fragrance has the following structural formula: # imgabs0 #. The phenolic compound prepared by the preparation method disclosed by the invention is named as 3-methyl-6-allyl-2-methoxy-4-bromophenol, and the phenolic compound has a sweet aroma, a special aromatic aroma and a guaiaeda charm; the phenolic compound is elegant in fragrance and long in fragrance holding time and has important application value and market prospects in the field of daily chemical flavor blending, and the preparation method is simple in process, convenient to control, high in production efficiency and beneficial to large-scale production. Compared with the caramel sweet guaiacol base without the phenolic compound, the caramel sweet guaiacol base prepared by the invention has more prominent caramel sweet fragrance, more prominent characteristic burnt fragrance and slight elegant guaiacol note by adding the phenolic compound with the caramel sweet fragrance, and the fragrance quality of the base is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flavors and fragrances, and specifically relates to a phenolic compound with a caramel-like sweet aroma, a preparation method thereof, and a caramel-like sweet guaiac wood base. Background Art

[0002] With the rapid development of the flavors and fragrances industry, the varieties of natural and synthetic flavors and fragrances are increasing day by day, and the flavoring techniques are becoming increasingly sophisticated. In the fields of daily chemical products, food, heated tobacco products, etc., flavors and fragrances are often used as fixatives, co-ordinators or flavoring agents, etc., to enhance the aroma and sensory experience of heated tobacco products. Therefore, developing new fragrance compounds with unique aromas and sensory experiences and suitable as flavors and fragrances, enriching the varieties of flavors and fragrances, and further enriching the aroma and sensory experience of products, and promoting the development of the flavors and fragrances industry have good social and economic values. Summary of the Invention

[0003] In order to overcome the disadvantages and deficiencies existing in the prior art, the purpose of the present invention is to provide a phenolic compound, which has a caramel-like sweet aroma, a special aromatic fragrance, and a guaiac wood note; the phenolic compound has an elegant aroma and a long-lasting fragrance, and has important application value and market prospects in the field of daily chemical flavoring.

[0004] Another purpose of the present invention is to provide a preparation method of a phenolic compound with a caramel-like sweet aroma. The preparation method uses a microwave-assisted Claisen rearrangement reaction to prepare a new phenolic compound with a caramel-like sweet aroma. The preparation method has a simple process, is easy to operate, has high production efficiency, and is conducive to large-scale production.

[0005] Another purpose of the present invention is to provide a caramel-like sweet guaiac wood base, which is added with the above-mentioned phenolic compound with a caramel-like sweet aroma. Compared with the caramel-like sweet guaiac wood base without adding this phenolic compound, it has a more prominent caramel-like sweet aroma, a more prominent characteristic burnt and aromatic fragrance, and a slightly elegant guaiac wood note, and the aroma quality of the base is significantly improved.

[0006] The purpose of the present invention is achieved by the following technical solutions: A phenolic compound with a caramel-like sweet aroma has the following structural formula: .

[0007] The phenolic compound with a caramel-like sweet aroma can be named as: 3-methyl-6-allyl-2-methoxy-4-bromophenol.

[0008] The phenolic compound with a caramel-like sweet aroma of the present invention has a special aromatic fragrance and a guaiac wood note, and has important uses in the field of daily chemical flavoring.

[0009] Another object of the present invention is achieved by the following technical solution: A preparation method of phenolic compounds with a caramel-like sweet aroma, comprising the following steps: Step 1: Using 2-methoxy-3-methylphenol as the preparation raw material, prepare 3-methyl-2-methoxy-4-bromophenol. The structural formula of 2-methoxy-3-methylphenol is shown as follows: ; The structural formula of 3-methyl-2-methoxy-4-bromophenol is shown as follows: ; Step 2: Using the 3-methyl-2-methoxy-4-bromophenol prepared in Step 1 as the preparation raw material, prepare 3-methyl-2-methoxy-4-bromophenyl allyl ether. The structural formula of 3-methyl-2-methoxy-4-bromophenyl allyl ether is shown as follows: ; Step 3: Using the 3-methyl-2-methoxy-4-bromophenyl allyl ether prepared in Step 2 as the preparation raw material, after separation and purification, obtain phenolic compounds with a caramel-like sweet aroma. The phenolic compounds with a caramel-like sweet aroma are 3-methyl-6-allyl-2-methoxy-4-bromophenol.

[0010] Further, in Step 1, the preparation method of 3-methyl-2-methoxy-4-bromophenol comprises the following steps: A1. Take 2-methoxy-3-methylphenol, add it to DCM, cool to 0 °C, add PyHBr3, and react in an ice bath; after detecting the disappearance of the raw materials 2-methoxy-3-methylphenol or PyHBr3, place it in the ice bath again, add an aqueous solution of Na2SO3 to quench the reaction, and extract the aqueous phase with DCM; A2. Combine the organic phases, wash with hydrochloric acid, concentrate by drying, and separate by column chromatography to obtain 3-methyl-2-methoxy-4-bromophenol.

[0011] Further, in Step A1, take 1.1 - 1.4 mmol of 2-methoxy-3-methylphenol, add it to 5 - 7 mL of DCM, cool to 0 °C, add 1.3 - 1.7 mmol of PyHBr3, and react in an ice bath for 100 - 150 min.

[0012] Further, in Step 2, the preparation method of 3-methyl-2-methoxy-4-bromophenyl allyl ether comprises the following steps: B1. Add 3-methyl-2-methoxy-4-bromophenol, CH3CN, K2CO3, and 3-bromopropene to a reaction vessel, heat up and stir to react; B2. After the reaction is completed, cool to room temperature. After removing most of the acetonitrile by rotary evaporation, add water to the system to dissolve the obtained white solid, then extract with EA, dry and concentrate the combined organic phase, and separate by column chromatography to obtain a colorless liquid, namely 3-methyl-2-methoxy-4-bromophenyl allyl ether.

[0013] Further, in the step B1, add 0.6 - 0.7 mmol of 3-methyl-2-methoxy-4-bromophenol, 4 - 6 mL of CH3CN, 1.2 - 1.4 mmol of K2CO3, and 0.8 - 1 mmol of 3-bromopropene to the reaction vessel, heat to 62 - 68 °C and stir for 11 - 13 h.

[0014] Further, in the third step, put the 3-methyl-2-methoxy-4-bromophenyl allyl ether prepared in the second step into a microwave reactor for microwave treatment and stir. The microwave reaction conditions are to heat to 180 - 190 °C, maintain this temperature range for 2.5 - 3.5 h, and the system pressure during the reaction is 3.5 - 4.5 bar; after the reaction is completed, separate by column chromatography to obtain 3-methyl-6-allyl-2-methoxy-4-bromophenol.

[0015] Further, in the third step, put the 3-methyl-2-methoxy-4-bromophenyl allyl ether into a microwave reactor for microwave treatment, and put a magnetic stirring bar into the microwave reactor.

[0016] Another object of the present invention is achieved by the following technical solution: A caramel guaiacwood base, comprising the following raw materials in parts by weight: 45 - 55 parts of guaiacol, 4 - 6 parts of ethyl acetate, 16 - 20 parts of nonanol, 13 - 17 parts of heptanal, 20 - 24 parts of geranyl acetate, 37 - 43 parts of anisaldehyde, 16 - 20 parts of ethyl butyrate, 36 - 40 parts of ethyl maltol, 4 - 6 parts of ethyl caproate, 23 - 27 parts of peony nitrile, 7 - 9 parts of allyl hexanoate, 65 - 75 parts of ethyl heptanoate, 1.5 - 2.5 parts of 3-cyclohexylpropyl acrylate, 7 - 9 parts of cyclogopone ester, 30 - 40 parts of 3-methyl-6-allyl-2-methoxy-4-bromophenol, and 620 - 700 parts of propylene glycol.

[0017] The beneficial effects of the present invention are as follows: (1) The present invention creatively prepares a phenolic compound, named 3-methyl-6-allyl-2-methoxy-4-bromophenol, which has a caramel-like fragrance, a special aromatic aroma, and a guaiacwood note; this phenolic compound has an elegant aroma and a long-lasting fragrance, and has important application value and market prospects in the field of daily chemical flavoring.

[0018] (2)The preparation method of the phenolic compound of the present invention uses a microwave-assisted Claisen rearrangement reaction to obtain a new phenolic compound with a caramel-like aroma. This preparation method has a simple process, is easy to operate, has high production efficiency, and is conducive to large-scale production.

[0019] (3)The caramel-like guaiacwood base prepared by the present invention has a more prominent caramel-like aroma compared with the caramel-like guaiacwood base without adding the above-mentioned phenolic compound with a caramel-like aroma. The characteristic burnt and aromatic aroma is more prominent, and it also has a slightly elegant guaiacwood aroma rhyme, and the aroma quality of the base is significantly improved. Description of the Drawings

[0020] Figure 1 It is the hydrogen spectrum of 3-methyl-6-allyl-2-methoxy-4-bromophenol prepared in Example 1.

[0021] Figure 2 It is the carbon spectrum of 3-methyl-6-allyl-2-methoxy-4-bromophenol prepared in Example 1.

[0022] Figure 3 It is the gas chromatogram of 3-methyl-6-allyl-2-methoxy-4-bromophenol prepared in Example 1. Detailed Embodiments

[0023] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with the embodiments and the attached Figure 1 drawings. The content mentioned in the embodiments is not a limitation to the present invention.

[0024] In the embodiments of the present invention, a phenolic compound with a caramel-like aroma has the following structural formula: .

[0025] The phenolic compound with a caramel-like aroma can be named: 3-methyl-6-allyl-2-methoxy-4-bromophenol.

[0026] In the embodiment of the present invention, a preparation method of a phenolic compound with a caramel-like aroma includes the following steps: Step 1: Using 2-methoxy-3-methylphenol as the preparation raw material to prepare 3-methyl-2-methoxy-4-bromophenol. The structural formula of 2-methoxy-3-methylphenol is shown as follows: ; The structural formula of 3-methyl-2-methoxy-4-bromophenol is shown as follows: ; Step 2: Using the 3-methyl-2-methoxy-4-bromophenol prepared in Step 1 as a starting material, prepare 3-methyl-2-methoxy-4-bromophenyl allyl ether. The structural formula of 3-methyl-2-methoxy-4-bromophenyl allyl ether is shown as follows: ; Step 3: Using the 3-methyl-2-methoxy-4-bromophenyl allyl ether prepared in Step 2 as a starting material, after separation and purification, a phenolic compound with a caramel-like aroma is obtained. The phenolic compound with a caramel-like aroma is 3-methyl-6-allyl-2-methoxy-4-bromophenol.

[0027] In some embodiments of the present invention, in Step 1, the preparation method of 3-methyl-2-methoxy-4-bromophenol includes the following steps: A1. Take 2-methoxy-3-methylphenol, add it to DCM, cool to 0 °C, add PyHBr3, and react in an ice bath; after the raw materials are completely disappeared, place it in the ice bath again, add an aqueous solution of Na2SO3 to quench the reaction, and extract the aqueous phase with DCM; A2. Combine the organic phases, wash with hydrochloric acid, concentrate by drying, and separate by column chromatography to obtain 3-methyl-2-methoxy-4-bromophenol.

[0028] In some embodiments of the present invention, in Step A1, take 1.1 - 1.4 mmol of 2-methoxy-3-methylphenol, add it to 5 - 7 mL of DCM, cool to 0 °C, add 1.3 - 1.7 mmol of PyHBr3, and react in an ice bath for 100 - 150 min.

[0029] In some embodiments of the present invention, in Step 2, the preparation method of 3-methyl-2-methoxy-4-bromophenyl allyl ether includes the following steps: B1. Add 3-methyl-2-methoxy-4-bromophenol, CH3CN, K2CO3, and 3-bromopropene to a reaction vessel, heat up and stir the reaction; B2. After the reaction is completed, cool to room temperature, remove most of the acetonitrile by rotary evaporation, add water to dissolve the obtained white solid to the system, then extract with EA (20 mL × 3), dry and concentrate the combined organic phases, and separate by column chromatography (silicagel, Hex / EA = 50 : 1) to obtain a colorless liquid, that is, 3-methyl-2-methoxy-4-bromophenyl allyl ether.

[0030] In some embodiments of the present invention, in step B1, 0.6 - 0.7 mmol of 3 - methyl - 2 - methoxy - 4 - bromophenol, 4 - 6 mL of CH3CN, 1.2 - 1.4 mmol of K2CO3, and 0.8 - 1 mmol of 3 - bromopropene are added to a reaction vessel, and the temperature is raised to 62 - 68 °C and stirred for 11 - 13 h.

[0031] In some embodiments of the present invention, in step three, the 3 - methyl - 2 - methoxy - 4 - bromophenyl allyl ether prepared in step two is placed in a microwave reactor for microwave treatment, and a magnetic stirring bar is added. The microwave reaction conditions are to raise the temperature to 180 - 190 °C and maintain this temperature range for 2.5 - 3.5 h, and the system pressure during the reaction is 3.5 - 4.5 bar; after the reaction, 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol is obtained by column chromatography separation.

[0032] In some embodiments of the present invention, a caramel - like guaiac wood base includes the following raw materials in parts by weight: 45 - 55 parts of guaiacol, 4 - 6 parts of ethyl acetate, 16 - 20 parts of nonanol, 13 - 17 parts of heptanal, 20 - 24 parts of geranyl acetate, 37 - 43 parts of anisaldehyde, 16 - 20 parts of ethyl butyrate, 36 - 40 parts of ethyl maltol, 4 - 6 parts of ethyl hexanoate, 23 - 27 parts of peony nitrile, 7 - 9 parts of allyl hexanoate, 65 - 75 parts of ethyl heptanoate, 1.5 - 2.5 parts of 3 - cyclohexylpropyl acrylate, 7 - 9 parts of cyclogopone ester, 30 - 40 parts of 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol, and 620 - 700 parts of propylene glycol.

[0033] In a typical embodiment of the present invention, a caramel - like guaiac wood base includes the following raw materials in parts by weight: 50 parts of guaiacol, 5 parts of ethyl acetate, 18 parts of nonanol, 15 parts of heptanal, 22 parts of geranyl acetate, 40 parts of anisaldehyde, 18 parts of ethyl butyrate, 38 parts of ethyl maltol, 5 parts of ethyl hexanoate, 25 parts of peony nitrile, 8 parts of allyl hexanoate, 70 parts of ethyl heptanoate, 2 parts of 3 - cyclohexylpropyl acrylate, 8 parts of cyclogopone ester, 35 parts of 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol, and 641 parts of propylene glycol.

[0034] Example 1 This example provides a phenolic compound with a caramel - like aroma, having the following structural formula: 。

[0035] The chemical name of the phenolic compound with a caramel - like aroma is: 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol.

[0036] The preparation method of the phenolic compound with a caramel - like aroma includes the following steps: Step 1: Prepare 3-methyl-2-methoxy-4-bromophenol. The chemical reaction formula for the preparation of 3-methyl-2-methoxy-4-bromophenol is as follows:

[0037] A1. Take 2-methoxy-3-methylphenol (177 mg, 1.28 mmol), add it to DCM (6 mL), cool to 0 °C, and slowly add PyHBr3 (520 mg, 1.54 mmol); react in an ice bath for 2 h. After the reaction of 2-methoxy-3-methylphenol is complete, place it in an ice bath again, add Na2SO3(aq.) to quench the reaction, and extract the aqueous phase with DCM (20 mL×3); the structural formula of 2-methoxy-3-methylphenol is as shown in Formula 1; A2. Combine the organic phases, wash three times with 10% HCl (aq.), dry and concentrate, and separate by column chromatography (silicagel, Hex / EA = 10 : 1) to obtain 221 mg of a light brown liquid, which is 3-methyl-2-methoxy-4-bromophenol, with a yield of 80%; the structural formula of 3-methyl-2-methoxy-4-bromophenol is as shown in Formula 2, and it has the following NMR spectral characteristics: 1 H NMR (500 MHz, CDCl3) δ 7.20 (d, J = 8.7 Hz, 1H), 6.72 (d, J = 8.7 Hz,1H), 5.74 (s, 1H), 3.77 (s, 3H), 2.34 (s, 3H); 13 C NMR (125 MHz, CDCl3) δ 148.3, 146.1, 131.3, 128.4, 115.3, 114.3,61.1, 16.4。

[0038] The mass spectrometry analysis data is as follows: HRMS (ESI / [M + Na] + );The theoretically calculated data of high-resolution electrospray ionization mass spectrometry for C8H9BrO2 is 238.9678, and the actually measured value is 238.967 (HRMS (ESI / [M + Na] + ) calculated for C8H9BrO2:238.9678 found238.9674).

[0039] Step 2: Prepare 3-methyl-2-methoxy-4-bromophenyl allyl ether. The chemical reaction formula for the preparation of 3-methyl-2-methoxy-4-bromophenyl allyl ether is as follows:

[0040] B1. Add 3-methyl-2-methoxy-4-bromophenol (139 mg, 0.64 mmol), CH3CN (5 mL), K2CO3 (177 mg, 1.28 mmol) and 3-bromopropene (0.1 mL, 1.0 mmol) into a flask, heat to 65 °C and stir for 12 h; B2. After the reaction is completed, cool to room temperature. After removing most of the acetonitrile by rotary evaporation, add water (20 mL) to the system to dissolve the white solid, then extract with EA (20 mL × 3). Dry and concentrate the combined organic phases, and separate by column chromatography (silicagel, Hex / EA = 50:1) to obtain 156 mg of a colorless liquid, which is 3-methyl-2-methoxy-4-bromophenyl allyl ether, with a yield and content of 95%. The structural formula of 3-methyl-2-methoxy-4-bromophenyl allyl ether is shown in Formula 3, and it has the following NMR spectral characteristics: 1 H NMR (500 MHz, CDCl3) δ 7.20 (d, J = 8.8 Hz, 1H), 6.64 (d, J = 8.8 Hz,1H), 6.06 (ddt, J = 17.2, 10.4, 5.1 Hz, 1H), 5.43 (dd, J = 17.3, 1.6 Hz, 1H),5.29 (dd, J = 10.6, 1.4 Hz, 1H), 4.54 (dt, J = 5.1, 1.5 Hz, 2H), 3.82 (s, 3H),2.35 (s, 3H); 13 C NMR (125 MHz, CDCl3) δ 151.1, 148.5, 133.1, 132.4, 127.2, 117.6,116.4, 112.7, 69.6, 60.4, 16.2.

[0041] The mass spectrometry analysis data are as follows: HRMS (ESI / [M + Na] + ) ; The theoretically calculated data of high-resolution electrospray ionization mass spectrometry is C 11 H13 BrO2: 278.9991, the actually measured value is 280.0003 (HRMS (ESI / [M + Na] + ) calculated for C 11 H 13 BrO2: 278.9991, found 280.0003).

[0042] Step 3: Prepare 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol. The chemical reaction formula for the preparation of 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol is as follows:

[0043] The preparation method of 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol is as follows: Place 3 - methyl - 2 - methoxy - 4 - bromophenyl allyl ether (12.3 g, 47.8 mmol) in a 30 mL thick - walled glass microwave reaction flask, and add a magnetic stirrer. Without adding a solvent, directly place it in a microwave reactor. Set the microwave reaction conditions to rapidly heat up to 185 °C and maintain this temperature for 3 h. The system pressure during the reaction is 4.0 bar; after the reaction, the system turns dark brown. Without further treatment, directly separate it by column chromatography (silica gel, Hex / EA = 20:1) to obtain 6.8 g of a light brown liquid, which is 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol. Its structural formula is as shown in Formula 4, and the yield is 48%.

[0044] The 3 - methyl - 6 - allyl - 2 - methoxy - 4 - bromophenol prepared in this example has the following NMR spectral characteristics: 1 H NMR (500 MHz, CDCl3) δ 7.11 (s, 1H), 6.02 – 5.93 (m, 1H), 5.75 (s,1H), 5.13 – 5.10 (m, 1H), 5.09 (t, J J = 1.4 Hz, 1H), 3.77 (s, 3H), 3.36 (d, J J = 6.6 Hz, 2H), 2.33 (s, 3H); 13 C NMR (125 MHz, CDCl3) δ 146.2, 145.8, 135.9, 128.7, 128.7, 125.9,116.2, 114.9, 61.1, 33.6, 16.2。

[0045] The mass spectrometry analysis data is as follows: HRMS (ESI / [M + Na] + ) The theoretically calculated data of high-resolution electrospray ionization mass spectrometry for C 11 H 13 BrO2: 278.9991, and the actually measured value is 280.0002 (HRMS (ESI / [M + Na] + ) calculated for C 11 H 13 BrO2: 278.9991, found 280.0002).

[0046] Example 2 The aroma rating, fragrance retention test, and base fragrance aroma test were carried out on 3-methyl-6-allyl-2-methoxy-4-bromophenol prepared in Example 1, and the test results are as follows: (1) Aroma evaluation: Fourteen perfumers with more than 5 years of work experience made the following evaluation of the aroma of this compound: Fourteen perfumers unanimously agreed that this compound presented a caramel-like sweet aroma in addition to having a special aromatic aroma with a guaiac woody note.

[0047] (2) Fragrance retention test: A propylene glycol solution with a mass fraction of 10% of 3-methyl-6-allyl-2-methoxy-4-bromophenol was prepared. One smelling strip was taken, dipped in a little, and the strip was placed on the smelling rack. Three perfumers smelled it every 2 hours. When more than or equal to 2 perfumers could not perceive the aroma of the smelling strip, the fragrance retention time was recorded..

[0048] The fragrance retention test showed that the fragrance retention time of the caramel-like sweet aroma of 3-methyl-6-allyl-2-methoxy-4-bromophenol was 48 hours, and the fragrance retention time of the special aromatic odor and guaiac woody note was 72 hours.

[0049] (3) Base fragrance aroma test: The base fragrance formula is shown in the following table:

[0050] Base fragrance A and base fragrance B were prepared according to the above formula. 35 parts of the target product 3-methyl-6-allyl-2-methoxy-4-bromophenol of the present invention were added to base fragrance B. Seven perfumers with more than 5 years of work experience made the following evaluation after smelling the above base fragrances: Seven perfumers unanimously agreed that base fragrance B had a more prominent caramel-like sweet aroma than base fragrance A, with a more prominent characteristic burnt and aromatic aroma, slightly with an elegant guaiac woody note, and the quality of the base fragrance aroma was significantly improved.

[0051] The above embodiments are preferred implementation solutions of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious substitution without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A phenolic compound with a caramel-like sweet aroma, characterized in that: It has the following structural formula:

2. A method for preparing a phenolic compound having a caramel-like sweet aroma as described in claim 1, characterized in that: It includes the following steps: Step 1: Using 2-methoxy-3-methylphenol as the preparation raw material, prepare 3-methyl-2-methoxy-4-bromophenol. The structural formula of 2-methoxy-3-methylphenol is shown as follows: The structural formula of 3-methyl-2-methoxy-4-bromophenol is shown as follows: Step 2: Using the 3-methyl-2-methoxy-4-bromophenol prepared in Step 1 as the preparation raw material, prepare 3-methyl-2-methoxy-4-bromophenyl allyl ether. The structural formula of 3-methyl-2-methoxy-4-bromophenyl allyl ether is shown as follows: Step 3: Using the 3-methyl-2-methoxy-4-bromophenyl allyl ether prepared in Step 2 as the preparation raw material, after separation and purification, obtain a phenolic compound with a caramel-like sweet fragrance. The phenolic compound with a caramel-like sweet fragrance is 3-methyl-6-allyl-2-methoxy-4-bromophenol.

3. The preparation method of the phenolic compound with a caramel-like sweet aroma according to claim 2, characterized in that: In the said Step 1, the preparation method of 3-methyl-2-methoxy-4-bromophenol includes the following steps: A1. Take 2-methoxy-3-methylphenol, add it to DCM, cool to 0 °C, add PyHBr3, and react in an ice bath; after the raw material 2-methoxy-3-methylphenol or PyHBr3 completely disappears, place it in the ice bath again, add an aqueous solution of Na2SO3 to quench the reaction, and extract the aqueous phase with DCM; A2. Combine the organic phases, wash with hydrochloric acid, concentrate by drying, and separate by column chromatography to obtain 3-methyl-2-methoxy-4-bromophenol.

4. The preparation method of the phenolic compound with caramel-like sweet aroma according to claim 3, characterized in that: In the said Step A1, take 1.1 - 1.4 mmol of 2-methoxy-3-methylphenol, add it to 5 - 7 mL of DCM, cool to 0 °C, add 1.3 - 1.7 mmol of PyHBr3, and react in an ice bath for 100 - 150 min.

5. The preparation method of the phenolic compound with a caramel-like sweet aroma according to claim 2, characterized in that: In the said Step 2, the preparation method of 3-methyl-2-methoxy-4-bromophenyl allyl ether includes the following steps: B1. Add 3-methyl-2-methoxy-4-bromophenol, CH3CN, K2CO3, and 3-bromopropene to a reaction vessel, heat up and stir the reaction; B2. After the reaction is completed, cool to room temperature, remove most of the acetonitrile by rotary evaporation, add water to dissolve the obtained white solid to the system, then extract with EA, dry and concentrate the combined organic phases, and separate by column chromatography to obtain a colorless liquid, that is, 3-methyl-2-methoxy-4-bromophenyl allyl ether.

6. The preparation method of the phenolic compound with caramel-like sweet aroma according to claim 5, characterized in that: In the said Step B1, add 0.6 - 0.7 mmol of 3-methyl-2-methoxy-4-bromophenol, 4 - 6 mL of CH3CN, 1.2 - 1.4 mmol of K2CO3, and 0.8 - 1 mmol of 3-bromopropene to a reaction vessel, heat up to 62 - 68 °C and stir for 11 - 13 h.

7. The preparation method of the phenolic compound with a caramel-like sweet aroma according to claim 2, characterized in that: In Step 3, the 3-methyl-2-methoxy-4-bromophenyl allyl ether prepared in Step 2 is placed in a microwave reactor for microwave treatment with stirring. The microwave reaction conditions are as follows: heating to 180 - 190 °C and maintaining this temperature range for 2.5 - 3.5 h, with the system pressure during the reaction being 3.5 - 4.5 bar; after the reaction, 3-methyl-6-allyl-2-methoxy-4-bromophenol is obtained by column chromatography separation.

8. The preparation method of the phenolic compound with a caramel-like sweet aroma according to claim 2, characterized in that: In Step 3, the 3-methyl-2-methoxy-4-bromophenyl allyl ether is placed in a microwave reactor for microwave treatment, and a magnetic stir bar is placed in the microwave reactor.

9. A caramelized guaiacwood base, characterized in that: It comprises the following raw materials in parts by weight: 45 - 55 parts of guaiacol, 4 - 6 parts of ethyl acetate, 16 - 20 parts of nonanol, 13 - 17 parts of heptaldehyde, 20 - 24 parts of geranyl acetate, 37 - 43 parts of anisaldehyde, 16 - 20 parts of ethyl butyrate, 36 - 40 parts of ethyl maltol, 4 - 6 parts of ethyl hexanoate, 23 - 27 parts of peony nitrile, 7 - 9 parts of allyl hexanoate, 65 - 75 parts of ethyl heptanoate, 1.5 - 2.5 parts of 3-cyclohexylpropyl acrylate, 7 - 9 parts of cyclogeranium ester, 30 - 40 parts of 3-methyl-6-allyl-2-methoxy-4-bromophenol, and 620 - 700 parts of propylene glycol.

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