Ester compound with grass sweet fragrance, preparation method thereof and grass sweet fragrance base

Abstract

The invention relates to the technical field of flavors and fragrances, in particular to an ester compound with grass sweet fragrance, a preparation method of the ester compound and a grass sweet fragrance base. The ester compound with the grass sweet fragrance has the following structural formula: the ester compound with the grass sweet fragrance prepared by the invention is 4-(5-bromo-1H-indene-3-yl) methyl butyrate, and the compound has special aromatic fragrance and violet fragrance, and is elegant in fragrance and long in fragrance retention time. The preparation method of the compound is simple in process, convenient to operate and control, high in production efficiency and suitable for industrial production. Compared with the flower and plant sweet fragrance base without the compound, the flower and plant sweet fragrance base prepared by the invention is added with the ester compound with the grass sweet fragrance, so that the flower and plant sweet fragrance base has more prominent grass sweet fragrance, special grass fragrance accompanied by fresh and sweet fragrance and stronger violet flower fragrance note, and the fragrance quality of the base is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of fragrance and flavor technology, specifically to an ester compound with a grassy sweet aroma, its preparation method, and a floral and grassy sweet aroma base. Background Technology

[0002] Traditional violet fragrances rely on ionone compounds, but these molecules tend to have similar aroma characteristics. For example, the rose fragrance formula disclosed in patent CN110229717A, while simulating rose aroma through components such as phenylethyl alcohol and citronellol, does not involve the innovative construction of violet aroma. Similarly, although the tobacco flavoring industry has attempted to combine violet with tobacco aroma (such as the preparation method of a tobacco violet flower extract in patent CN201610896435.8), this is limited to aroma modification and has not broken through the chemical structure bottleneck of violet fragrance itself. In addition, the longevity of ionones is limited by their chemical structural stability, making them susceptible to factors such as light and oxidation in daily chemical products, resulting in insufficient aroma persistence. In view of this, the present invention has developed an ester compound with a grassy sweet aroma, giving the compound a special aromatic fragrance with a violet scent. This chemical has an elegant aroma and a long-lasting fragrance, making it important for use in the daily chemical fragrance industry. Currently, no domestic or international fragrance and flavor companies have launched this compound. Therefore, this compound has significant applications and broad market prospects in the fragrance field. Summary of the Invention

[0003] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide an ester compound with a grassy sweet aroma. The compound has a special aromatic fragrance with a violet fragrance, an elegant aroma, and a long-lasting fragrance. It has important application value and market prospects in the field of perfumery.

[0004] Another objective of this invention is to provide a method for preparing an ester compound with a grassy sweet aroma. The preparation method is simple, easy to operate and control, has high production efficiency, and is suitable for industrial production.

[0005] Another object of the present invention is to provide a grassy sweet fragrance base, wherein the grassy sweet fragrance base is added with the above-mentioned ester compound having a grassy sweet fragrance, and compared with the floral grassy sweet fragrance base without the addition of the compound, it has a more prominent grassy sweet fragrance, a distinctive grassy fragrance accompanied by a sweet fragrance, and a stronger violet fragrance, and the fragrance base fragrance quality is significantly improved.

[0006] The objective of this invention is achieved through the following technical solution: an ester compound with a sweet, grassy aroma, having the following structural formula:

[0007]

[0008] The ester compound with a grassy sweet aroma can be named: methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

[0009] The ester compounds of the present invention, which have a grassy sweet aroma, are prepared by the key Wittig reaction and olefin transfer catalyzed by trifluoroacetic acid. They have a special aromatic fragrance with a violet scent and are of great use in the field of daily chemical fragrance.

[0010] Another objective of this invention is achieved through the following technical solution: a method for preparing an ester compound with a grassy sweet aroma, comprising the following steps:

[0011] Step 1: Using brominated compound 1 and triphenylphosphine as raw materials, (4-methoxy-4-oxobutyl)triphenylphosphine bromide was prepared. The structural formula of brominated compound 1 is shown below:

[0012]

[0013] The structural formula of (4-methoxy-4-oxobutyl)triphenylphosphine bromide is shown below:

[0014]

[0015] Step 2: Using brominated compound 2 and (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in Step 1 as raw materials, an intermediate is prepared. The structural formula of brominated compound 2 is shown below:

[0016]

[0017] The structural formula of the intermediate is shown below:

[0018]

[0019] Step 3: Using the intermediate obtained in Step 3 as the raw material, and after separation and purification, an ester compound with a sweet grassy aroma is obtained, wherein the ester compound with a sweet grassy aroma is methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

[0020] Furthermore, the (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in step two is a known compound, which is mentioned in Franke, I.; Binder, M. Helv. Chim. Acta. 1980, 63, 2508-2514.

[0021] Furthermore, in step one, the preparation method of (4-methoxy-4-oxobutyl)triphenylphosphine bromide includes the following steps:

[0022] A1. Place the bromine compound I in a reaction vessel, add a toluene solution of triphenylphosphine, heat to 100-120℃ under light and reflux, and maintain the reaction for 22-26 hours.

[0023] A2. After the raw materials in the reaction flask have completely disappeared, cool to room temperature. A white solid will precipitate out. Filter through a Buchner funnel to obtain a white solid, which is (4-methoxy-4-oxobutyl)triphenylphosphine bromide.

[0024] Furthermore, in step A1, 5-6 mol of the brominated compound is placed in a reaction vessel, and 1200-1800 mL of a toluene solution of triphenylphosphine is added, wherein the triphenylphosphine content is 6-7 mol. The mixture is heated to 100-120°C under light and refluxed, and the reaction is maintained for 22-26 hours.

[0025] Furthermore, in step two, the preparation method of the intermediate includes the following steps:

[0026] B1. Under argon protection, dissolve the (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in step one in THF and place it in a reaction flask. After cooling to -1 to -1°C in an ice bath, slowly add KHMDS solution. After reacting for 0.8 to 1.2 h, dissolve the brominated compound II in THF solution and slowly add it to the reaction system. Heat to room temperature and react for 12 to 18 h.

[0027] B2. After the reaction is complete, water and saturated saline solution are added to the reaction flask to quench the reaction. The organic phase is then separated, and the organic phase in the aqueous phase is extracted using EA. The two organic phases are dried, concentrated, and combined. The yellow liquid is obtained by column chromatography, which is the intermediate.

[0028] Furthermore, in step B1, under argon protection, 130-140g of (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in step one is dissolved in 550-650mL of THF and placed in a reaction flask. After cooling to -1 to 1℃ in an ice bath, 200-300mL of 0.8-1.2mol / L KHMDS solution is slowly added. After reacting for 0.8-1.2h, 40-50g of brominated compound II is dissolved in 250-300mL of THF solution and slowly added to the reaction system. The temperature is raised to room temperature and the reaction is carried out for 12-18h.

[0029] Furthermore, in step three, the preparation method of methyl 4-(5-bromo-1H-inden-3-yl)butyrate includes the following steps:

[0030] C1. Add the intermediate obtained in step 2, chloroform and trifluoroacetic acid to the reaction flask in sequence, and stir vigorously for 2-4 hours.

[0031] C2. After the reaction is complete, the reactants obtained in step C1 are diluted with dichloromethane, and then saturated sodium bicarbonate solution is added to quench the reaction. The organic phase is separated, and the organic phase in the aqueous phase is extracted with dichloromethane. The two organic phases are dried, concentrated and combined, and separated by column chromatography to obtain a yellow oily liquid, which is the methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

[0032] Furthermore, in step C1, 40-50g of the intermediate obtained in step two, 450-550mL of chloroform and 45-55mL of trifluoroacetic acid are added sequentially to the reaction flask, and the mixture is stirred vigorously for 2-4 hours.

[0033] Another objective of this invention is achieved through the following technical solution: a floral sweet fragrance base, comprising the following raw materials in parts by weight: 45-55 parts of methyl 4-(5-bromo-1H-indene-3-yl)butyrate, 8-12 parts of cyclohexane, 2-8 parts of vanillin, 25-35 parts of isoamyl acetate, 2-8 parts of galbanum alcohol, 2-8 parts of geraniol acetate, 12-16 parts of ethyl acrylate, 15-25 parts of ethyl butyrate, 2-6 parts of isoamyl butyrate, 75-85 parts of γ-caprolactone, 20-30 parts of linalool acetate, 75-85 parts of isomethyl ionone, 6-10 parts of allyl hexanoate, 15-25 parts of ethyl heptaate, 8-12 parts of allyl 3-cyclohexylpropionate, 6-10 parts of ethyl dihydroionone, and 600-700 parts of propylene glycol.

[0034] The beneficial effects of this invention are as follows: The ester compound with a grassy sweet aroma obtained by this invention is methyl 4-(5-bromo-1H-inden-3-yl)butyrate. This compound is prepared through a key Wittig reaction and olefin transfer catalyzed by trifluoroacetic acid. It possesses a unique aromatic fragrance with a violet scent, exhibiting an elegant aroma and long-lasting fragrance, making it significant in the perfumery field and possessing promising market prospects. The preparation method of this compound is simple, easy to operate and control, and has high production efficiency, making it suitable for industrial production. The grassy sweet aroma base obtained by this invention, with the addition of the aforementioned ester compound with a grassy sweet aroma, exhibits a more prominent grassy sweet aroma compared to grassy sweet aroma bases without this compound. It possesses a distinctive fresh grassy scent accompanied by a sweet aroma, with a stronger violet scent, significantly improving the quality of the aroma base. Attached Figure Description

[0035] Figure 1 The photon spectrum of methyl 4-(5-bromo-1H-indene-3-yl)butyrate prepared in Example 1 is shown.

[0036] Figure 2 The carbon spectrum of methyl 4-(5-bromo-1H-indene-3-yl)butyrate prepared in Example 1. Detailed Implementation

[0037] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0038] In an embodiment of the present invention, an ester compound having a grassy sweet aroma has the following structural formula:

[0039]

[0040] The ester compound with a grassy sweet aroma can be named: methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

[0041] In an embodiment of the present invention, a method for preparing an ester compound having a grassy sweet aroma includes the following steps:

[0042] Step 1: Using brominated compound 1 and triphenylphosphine as raw materials, (4-methoxy-4-oxobutyl)triphenylphosphine bromide was prepared. The structural formula of brominated compound 1 is shown below:

[0043]

[0044] The structural formula of (4-methoxy-4-oxobutyl)triphenylphosphine bromide is shown below:

[0045]

[0046] Step 2: Using brominated compound 2 and (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in Step 1 as raw materials, an intermediate is prepared. The structural formula of brominated compound 2 is shown below:

[0047]

[0048] The structural formula of the intermediate is shown below:

[0049]

[0050] Step 3: Using the intermediate obtained in Step 3 as the raw material, and after separation and purification, an ester compound with a sweet grassy aroma is obtained, wherein the ester compound with a sweet grassy aroma is methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

[0051] Furthermore, the (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in step two is a known compound, which is mentioned in Franke, I.; Binder, M. Helv. Chim. Acta. 1980, 63, 2508-2514.

[0052] Furthermore, in step one, the preparation method of (4-methoxy-4-oxobutyl)triphenylphosphine bromide includes the following steps:

[0053] A1. Place the bromine compound I in a reaction vessel, add a toluene solution of triphenylphosphine, heat to 100-120℃ under light and reflux, and maintain the reaction for 22-26 hours.

[0054] A2. After the raw materials in the reaction flask have completely disappeared, cool to room temperature. A white solid will precipitate out. Filter through a Buchner funnel to obtain a white solid, which is (4-methoxy-4-oxobutyl)triphenylphosphine bromide.

[0055] Furthermore, in step A1, 5-6 mol of the brominated compound is placed in a reaction vessel, and 1200-1800 mL of a toluene solution of triphenylphosphine is added, wherein the triphenylphosphine content is 6-7 mol. The mixture is heated to 100-120°C under light and refluxed, and the reaction is maintained for 22-26 hours.

[0056] Furthermore, in step two, the preparation method of the intermediate includes the following steps:

[0057] B1. Under argon protection, dissolve the (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in step one in THF and place it in a reaction flask. After cooling to -1 to -1°C in an ice bath, slowly add KHMDS solution. After reacting for 0.8 to 1.2 h, dissolve the brominated compound II in THF solution and slowly add it to the reaction system. Heat to room temperature and react for 12 to 18 h.

[0058] B2. After the reaction is complete, water and saturated saline solution are added to the reaction flask to quench the reaction. The organic phase is then separated, and the organic phase in the aqueous phase is extracted using EA. The two organic phases are dried, concentrated, and combined. The yellow liquid is obtained by column chromatography, which is the intermediate.

[0059] Furthermore, in step B1, under argon protection, 130-140g of (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in step one is dissolved in 550-650mL of THF and placed in a reaction flask. After cooling to -1 to 1℃ in an ice bath, 200-300mL of 0.8-1.2mol / L KHMDS solution is slowly added. After reacting for 0.8-1.2h, 40-50g of brominated compound II is dissolved in 250-300mL of THF solution and slowly added to the reaction system. The temperature is raised to room temperature and the reaction is carried out for 12-18h.

[0060] Furthermore, in step three, the preparation method of methyl 4-(5-bromo-1H-inden-3-yl)butyrate includes the following steps:

[0061] C1. Add the intermediate obtained in step 2, chloroform and trifluoroacetic acid to the reaction flask in sequence, and stir vigorously for 2-4 hours.

[0062] C2. After the reaction is complete, the reactants obtained in step C1 are diluted with dichloromethane, and then saturated sodium bicarbonate solution is added to quench the reaction. The organic phase is separated, and the organic phase in the aqueous phase is extracted with dichloromethane. The two organic phases are dried, concentrated and combined, and separated by column chromatography to obtain a yellow oily liquid, which is the methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

[0063] Furthermore, in step C1, 40-50g of the intermediate obtained in step two, 450-550mL of chloroform and 45-55mL of trifluoroacetic acid are added sequentially to the reaction flask, and the mixture is stirred vigorously for 2-4 hours.

[0064] In some embodiments of the present invention, a floral sweet fragrance base comprises the following raw materials in parts by weight: 45-55 parts of methyl 4-(5-bromo-1H-indene-3-yl)butyrate, 8-12 parts of cyclohexane, 2-8 parts of vanillin, 25-35 parts of isoamyl acetate, 2-8 parts of leucine alcohol, 2-8 parts of geraniol acetate, 12-16 parts of ethyl acrylate, 15-25 parts of ethyl butyrate, 2-6 parts of isoamyl butyrate, 75-85 parts of γ-caprolactone, 20-30 parts of linalool acetate, 75-85 parts of isomethyl ionone, 6-10 parts of allyl hexanoate, 15-25 parts of ethyl heptaate, 8-12 parts of allyl 3-cyclohexylpropionate, 6-10 parts of ethyl dihydroionone, and 600-700 parts of propylene glycol.

[0065] In a typical embodiment of the present invention, a floral sweet fragrance base comprises the following raw materials in parts by weight: 50 parts of methyl 4-(5-bromo-1H-indene-3-yl)butyrate, 10 parts of cyclohexane, 5 parts of vanillin, 30 parts of isoamyl acetate, 5 parts of leucine alcohol, 5 parts of geraniol acetate, 14 parts of ethyl acrylate, 20 parts of ethyl butyrate, 4 parts of isoamyl butyrate, 80 parts of γ-caprolactone, 25 parts of linaloyl acetate, 80 parts of isomethyl ionone, 8 parts of allyl hexanoate, 20 parts of ethyl heptaate, 10 parts of allyl 3-cyclohexylpropionate, 8 parts of ethyl dihydroionone, and 626 parts of propylene glycol.

[0066] Example 1

[0067] This embodiment provides an ester compound with a sweet, grassy aroma, having the following structural formula:

[0068]

[0069] The chemical name of the ester compound with a grassy sweet aroma is methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

[0070] The method for preparing the ester compound with a grassy sweet aroma includes the following steps:

[0071] Step 1: Preparation of (4-methoxy-4-oxobutyl)triphenylphosphine bromide. The chemical reaction formula for the preparation of (4-methoxy-4-oxobutyl)triphenylphosphine bromide is as follows:

[0072]

[0073] A1. Place 1000 g, 5.6 mol of brominated compound one in a reaction vessel, add a 1500 mL solution of triphenylphosphine (1600 g, 6.1 mol) in toluene, heat to 110 °C under light and reflux for 24 h; the structural formula of brominated compound one is shown in Formula 2.

[0074] A2. After the reactants in the reaction flask have completely disappeared, the mixture is cooled to room temperature. A white solid precipitates out and is filtered through a Buchner funnel to obtain 1700 g of white solid, which is (4-methoxy-4-oxobutyl)triphenylphosphine bromide, with a yield of 70%. The structural formula of (4-methoxy-4-oxobutyl)triphenylphosphine bromide is shown in Formula 3. (4-methoxy-4-oxobutyl)triphenylphosphine bromide is a known compound, mentioned in Franke, I.; Binder, M. Helv. Chim. Acta. 1980, 63, 2508-2514. It has the following NMR spectral characteristics:

[0075] 1 H NMR (600MHz, CDCl3) δ7.83 (ddd, J=12.7, 8.4, 1.3Hz, 6H), 7.78-7.71 (m, 3H), 7.66 (td, J=7.9, 3.5Hz, 6H) ,3.96(dddd,J=13.3,9.1,4.9,2.7Hz,2H),3.60(s,3H),2.85(td,J=6.6,1.4Hz,2H),1.95-1.82(m,2H).

[0076] 13 C NMR (150MHz, CDCl3) δ173.6,135.1,135.1,133.7,130.5,51.8,33.0,21.6,18.1.

[0077] Step 2: Preparation of intermediates. The chemical reaction formula for the preparation of intermediates is as follows:

[0078]

[0079] B1. Under argon protection, (4-methoxy-4-oxobutyl)triphenylphosphine bromide (136.8 g, 260 mmol) obtained in step one was dissolved in THF (600 mL) and placed in a reaction flask. After cooling to 0°C in an ice bath, KHMDS solution (260 mL, 1 M in THF, i.e., 1 mol KHMDS per liter of THF solution) was slowly added. After reacting for 1 h, brominated compound II (42 g, 200 mmol) was dissolved in THF (300 mL) and slowly added to the reaction system. The temperature was raised to room temperature and reacted for 15 h. The structural formula of brominated compound II is shown in Formula 4.

[0080] B2. After the reaction is complete, add water (100 mL) and saturated saline (400 mL) to the reaction flask to quench the reaction. Then separate the organic phase and extract the organic phase from the aqueous phase using EA (200 mL × 3). Dry, concentrate and combine the two organic phases. Separate them by column chromatography (silica gel, Hex / EA = 10:1) to obtain 47 g of yellow liquid, which is the intermediate prepared with a yield of 80%. The structural formula of the intermediate is shown in Formula 5. The yellow liquid product is a mixture of isomers and cannot be separated by simple silica gel column chromatography. It can be directly carried out in the next step (step 3).

[0081] Step 3: Prepare an ester compound with a sweet, grassy aroma, wherein the ester compound with a sweet, grassy aroma is methyl 4-(5-bromo-1H-inden-3-yl)butyrate; the chemical reaction formula for the preparation of methyl 4-(5-bromo-1H-inden-3-yl)butyrate is as follows:

[0082]

[0083] C1. Add the intermediate (47g, 160mmol) obtained in step 2, chloroform (500mL) and trifluoroacetic acid (50mL) to the reaction flask in sequence, and stir vigorously for 3h.

[0084] C2. After the reaction is complete, the reactants obtained in step C1 are diluted with dichloromethane (300 mL), and then quenched with saturated sodium bicarbonate solution (1000 mL). The organic phase is separated, and the organic phase in the aqueous phase is extracted with dichloromethane (200 mL × 3). The two organic phases are dried, concentrated, and combined. 44 g of yellow oily liquid is obtained by column chromatography (silica gel, Hex / EA = 10:1), which is the preparation of methyl 4-(5-bromo-1H-inden-3-yl)butyrate with a yield of 90%. The structural formula of methyl 4-(5-bromo-1H-inden-3-yl)butyrate is shown in Formula 1.

[0085] The methyl 4-(5-bromo-1H-inden-3-yl)butyrate prepared in this example has the following NMR spectral characteristics:

[0086] 1 H NMR (500MHz, CDCl3) δ7.57(dt,J=1.8,0.8Hz,1H),7.41(dd,J=8.1,1.8Hz,1H),7.21(d,J=8.1Hz,1H),6.25-6.18( m,1H),3.68(s,3H),3.35-3.27(m,2H),2.56(tq,J=8.2,1.8Hz,2H),2.41(t,J=7.4Hz,2H),2.00(p,J=7.5Hz,2H).

[0087] 13 C NMR (125MHz, CDCl3) δ173.9,146.6,144.2,143.1,129.2,128.8,127.1,120.3,118.9,51.6,37.7,33.7,27.1,23.2.

[0088] The mass spectrometry analysis data are as follows:

[0089] HRMS (ESI / [M+Na]) + The theoretical calculation data for high-resolution electrospray ionization mass spectrometry is C. 14 H 16 BrO2: 295.0328, actual measured value was 295.0330 (HRMS(ESI / [M+Na])). + ) calculated for C 14 H 16 BrO2:295.0328,found 295.0330.).

[0090] The FTIR (Fourier Transform Infrared Spectroscopy) data are as follows:

[0091] FTIR(Neat)2950(s),1736(s),1460(m),1142(m),1200(m),1167(m),860(m),819(m)cm -1 .

[0092] In thin-layer chromatography (TLC), the TLC result was: Rf = 0.35 (EA / Hex = 1:10).

[0093] Example 2

[0094] The methyl 4-(5-bromo-1H-inden-3-yl)butyrate prepared in Example 1 was subjected to aroma rating, longevity test, and aroma base test. The test results are as follows:

[0095] (1) Aroma evaluation: Eleven perfumers with more than five years of experience made the following evaluation of the aroma of the compound: The eleven perfumers unanimously agreed that in addition to presenting a grassy and sweet aroma, the compound also has a special aromatic aroma with the fragrance of violets.

[0096] (2) Scent retention test: Methyl 4-(5-bromo-1H-indene-3-yl)butyrate was prepared into a 10% propylene glycol solution. One scent test strip was taken, a small amount was dipped, and the test strip was placed on the scent rack. Three perfumers smelled it every 2 hours. When more than two perfumers could not perceive the scent of the scent test strip, the scent retention time was recorded.

[0097] Scent retention tests showed that methyl 4-(5-bromo-1H-indene-3-yl)butyrate had a scent retention time of 36 hours for its grassy sweetness and 50 hours for its special aromatic scent and violet fragrance.

[0098] (3) Aroma test of the base fragrance: The formula of the grassy sweet aroma base is shown in the table below:

[0099]

[0100] Prepare fragrance base A and fragrance base B according to the formula in the table above. The parts of each raw material in the table are by weight. Unlike fragrance base A, fragrance base B contains 50 parts of methyl 4-(5-bromo-1H-indene-3-yl)butyrate, the target product of this invention. After evaluating the fragrance base, nine perfumers with more than five years of experience made the following evaluation: The nine perfumers unanimously agreed that fragrance base B has a more prominent grassy and sweet aroma than fragrance base A. The characteristic grassy aroma is accompanied by a sweet aroma and has a stronger violet fragrance. The quality of the fragrance base is significantly improved.

[0101] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. An ester compound having a grassy, ​​sweet aroma, characterized in that: It has the following structural formula:

2. A method for preparing an ester compound with a sweet, grassy aroma as described in claim 1, characterized in that: Includes the following steps: Step 1: Using brominated compound 1 and triphenylphosphine as raw materials, (4-methoxy-4-oxobutyl)triphenylphosphine bromide was prepared. The structural formula of brominated compound 1 is shown below: The structural formula of (4-methoxy-4-oxobutyl)triphenylphosphine bromide is shown below: Step 2: Using brominated compound 2 and (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in Step 1 as raw materials, an intermediate is prepared. The structural formula of brominated compound 2 is shown below: The structural formula of the intermediate is shown below: Step 3: Using the intermediate obtained in Step 3 as the raw material, and after separation and purification, an ester compound with a sweet grassy aroma is obtained, wherein the ester compound with a sweet grassy aroma is methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

3. The method for preparing the ester compound with a grassy sweet aroma according to claim 2, characterized in that: In step one, the preparation method of (4-methoxy-4-oxobutyl)triphenylphosphine bromide includes the following steps: A1. Place the bromine compound I in a reaction vessel, add a toluene solution of triphenylphosphine, heat to 100-120℃ under light and reflux, and maintain the reaction for 22-26 hours. A2. After the raw materials in the reaction flask have completely disappeared, cool to room temperature. A white solid will precipitate out. Filter through a Buchner funnel to obtain a white solid, which is (4-methoxy-4-oxobutyl)triphenylphosphine bromide.

4. The method for preparing the ester compound with a grassy sweet aroma according to claim 3, characterized in that: In step A1, 5-6 mol of the brominated compound is placed in a reaction vessel, and 1200-1800 mL of a toluene solution of triphenylphosphine is added, wherein the triphenylphosphine content is 6-7 mol. The mixture is heated to 100-120°C under light protection and refluxed, and the reaction is maintained for 22-26 hours.

5. The method for preparing the ester compound with a grassy sweet aroma according to claim 2, characterized in that: In step two, the preparation method of the intermediate includes the following steps: B1. Under argon protection, dissolve the (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in step one in THF and place it in a reaction flask. After cooling to -1 to -1°C in an ice bath, slowly add KHMDS solution. After reacting for 0.8 to 1.2 h, dissolve the brominated compound II in THF solution and slowly add it to the reaction system. Heat to room temperature and react for 12 to 18 h. B2. After the reaction is complete, water and saturated saline solution are added to the reaction flask to quench the reaction. The organic phase is then separated, and the organic phase in the aqueous phase is extracted using EA. The two organic phases are dried, concentrated, and combined. The yellow liquid is obtained by column chromatography, which is the intermediate.

6. The method for preparing the ester compound with a grassy sweet aroma according to claim 5, characterized in that: In step B1, under argon protection, 130-140g of (4-methoxy-4-oxobutyl)triphenylphosphine bromide obtained in step one is dissolved in 550-650mL of THF and placed in a reaction flask. After cooling to -1 to 1℃ in an ice bath, 200-300mL of 0.8-1.2mol / L KHMDS solution is slowly added. After reacting for 0.8-1.2h, 40-50g of brominated compound II is dissolved in 250-300mL of THF solution and slowly added to the reaction system. The temperature is raised to room temperature and the reaction is carried out for 12-18h.

7. The method for preparing the ester compound with a grassy sweet aroma according to claim 2, characterized in that: In step three, the preparation method of methyl 4-(5-bromo-1H-inden-3-yl)butyrate includes the following steps: C1. Add the intermediate obtained in step 2, chloroform and trifluoroacetic acid to the reaction flask in sequence, and stir vigorously for 2-4 hours. C2. After the reaction is complete, the reactants obtained in step C1 are diluted with dichloromethane, and then saturated sodium bicarbonate solution is added to quench the reaction. The organic phase is separated, and the organic phase in the aqueous phase is extracted with dichloromethane. The two organic phases are dried, concentrated and combined, and separated by column chromatography to obtain a yellow oily liquid, which is the methyl 4-(5-bromo-1H-inden-3-yl)butyrate.

8. The method for preparing the ester compound with a grassy sweet aroma according to claim 7, characterized in that: In step C1, 40-50g of the intermediate obtained in step two, 450-550mL of chloroform and 45-55mL of trifluoroacetic acid are added sequentially to the reaction flask, and the mixture is stirred vigorously for 2-4 hours.

9. A floral sweet fragrance base, characterized in that: The raw materials include the following parts by weight: 45-55 parts of methyl 4-(5-bromo-1H-indene-3-yl)butyrate, 8-12 parts of cyclohexane, 2-8 parts of vanillin, 25-35 parts of isoamyl acetate, 2-8 parts of leucine alcohol, 2-8 parts of geraniol acetate, 12-16 parts of ethyl acrylate, 15-25 parts of ethyl butyrate, 2-6 parts of isoamyl butyrate, 75-85 parts of γ-caprolactone, 20-30 parts of linalool acetate, 75-85 parts of isomethyl ionone, 6-10 parts of allyl hexanoate, 15-25 parts of ethyl heptaate, 8-12 parts of allyl 3-cyclohexylpropionate, 6-10 parts of ethyl dihydroionone, and 600-700 parts of propylene glycol.

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