Preparation method and application of monatomic catalyst for synthesizing spiro compound from diol and naphthenic ketone

Abstract

The invention relates to the technical field of catalysts, in particular to a preparation method and application of a monatomic catalyst for synthesizing a spiro compound from diol and naphthenic ketone. A reaction formula for synthesizing a spiro compound from diol and naphthenic ketone is as follows: # imgabs0 #. The preparation method of the monatomic catalyst comprises the following steps: pretreating a carbon substrate; preparing a solution containing nickel salt; loading nickel atoms on the pretreated carbon substrate; and respectively roasting in inert gas and hydrogen-argon mixed gas.

Description

Technical Field

[0001] The present disclosure relates to the field of catalyst technology, and in particular to a preparation method and application of a single-atom catalyst for synthesizing spiro compounds from diols and cycloalkyl ketones. Background Art

[0002] Spiroalkane molecules are composed of two rings sharing one carbon. Spiro compounds have a rigid structure, stable structure, and special properties that are not possessed by general organic compounds, such as end group isomerism effect, spiro conjugation, and spiro hyperconjugation. Compared with monocyclic structures or planar aromatic structures, spiro structures have a larger three-dimensional structure; heterocyclic spiro compounds, especially oxygen heterocyclic spiro structures, can serve as bioisosteres of certain groups, which can change the water solubility, lipophilicity, dominant conformation and ADMET properties of drug molecules to a certain extent, making the optimized lead molecules easier to drug; however, there are currently few literatures that disclose the direct synthesis of oxygen heterospiro compounds using alcohols and cycloalkyl ketones. Summary of the invention

[0003] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a method for preparing a single-atom catalyst for synthesizing spirocyclic compounds from diols and cycloalkyl ketones to solve the deficiencies in the related art.

[0004] According to a first aspect of an embodiment of the present disclosure, a method for preparing a single-atom catalyst for synthesizing a spiro compound from a diol and a cycloalkyl ketone is provided. The reaction formula for synthesizing a spiro compound from a diol and a cycloalkyl ketone is as follows: wherein n1 and n2 are each independently selected from 0, 1 or 2; R1 is selected from C3-C5 alkyl, R2 and R3 are each independently selected from hydrogen, nitro, cyano, carboxyl, C1-C5 alkyl, C2-C5 alkenyl, C1-C10 alkoxy, or R2 and R3 are bonded to each other to form a C3-C8 cycloalkyl, C5-C12 aryl, 3-12 membered heterocyclyl or 5-12 membered heteroaryl; R4 is selected from hydrogen, nitro, cyano, carboxyl, C1-C5 alkyl, C2-C5 alkenyl or C1-C10 alkoxy; The preparation method of the single atom catalyst comprises the following steps: Step 1: providing a carbon substrate, and pretreating the carbon substrate to obtain a carbon substrate having oxygen-containing groups on the surface; Step 2: dissolving nickel salt in water, adding citric acid thereto to adjust the pH value, to obtain a first mixed solution; Step 3: adding the carbon substrate having oxygen-containing groups on the surface to the first mixed solution, stirring for 3-5 hours, and then filtering and drying to obtain a first solid; Step 4: calcine the first solid in an inert gas atmosphere for 5-8 hours, and then calcine in a hydrogen-argon mixed atmosphere for 2-4 hours. After filtering, washing and drying, the single atom catalyst is obtained.

[0005] In one aspect of the embodiments of the present disclosure, the carbon substrate is selected from graphene, carbon nanotubes or activated carbon. Specifically, the carbon substrate is selected from carbon nanotubes.

[0006] In one aspect of the embodiments of the present disclosure, in step 2, citric acid is added to adjust the pH value to 3.0-3.8; preferably, in step 2, citric acid is added to adjust the pH value to 3.2-3.5.

[0007] In one aspect of the embodiments of the present disclosure, in step 2, while the nickel salt is dissolved in water, a cobalt salt is also added.

[0008] In one aspect of the embodiments of the present disclosure, the ratio of the molar amount of the nickel element in the nickel salt to the molar amount of the cobalt element in the cobalt salt is selected from 1:(0.15-0.25).

[0009] In one aspect of the embodiments of the present disclosure, in step 1, the pretreatment includes placing the carbon substrate in an acidic solution for heating.

[0010] In one aspect of the embodiments of the present disclosure, the mass ratio of the nickel salt to the carbon substrate having oxygen-containing groups on the surface is selected from (1.5-3.5):100.

[0011] In one aspect of the embodiments of the present disclosure, in step 4, the calcination temperature under an inert gas atmosphere is selected from 550° C. to 650° C.

[0012] In one aspect of the embodiments of the present disclosure, in step 4, the calcination temperature in the hydrogen-argon mixed gas atmosphere is selected from 250° C. to 350° C.

[0013] In one aspect of the embodiments of the present disclosure, the ratio of the molar amount of the nickel element in the nickel salt to the molar amount of the cobalt element in the cobalt salt is selected from 1:(0.18-0.22).

[0014] In one aspect of the disclosed embodiment, step 4 comprises: placing the first solid in a tubular furnace, heating to 600°C at a heating rate of 5°C / min under a nitrogen atmosphere and calcining for 6 hours, then naturally cooling to 300°C, switching nitrogen to a hydrogen-argon mixture, calcining for 2.5 hours, and then naturally cooling to room temperature; then filtering, washing and drying to obtain the single atom catalyst.

[0015] In one aspect of the embodiments of the present disclosure, in step 4, the inert gas is nitrogen.

[0016] According to a second aspect of an embodiment of the present disclosure, a single atom catalyst is provided, wherein the single atom catalyst is prepared by the aforementioned method for preparing the single atom catalyst.

[0017] According to a third aspect of the embodiments of the present disclosure, a method for synthesizing a spiro compound is provided, wherein the method uses a diol and a cycloalkyl ketone as raw materials; wherein the diol has a structural formula of the following formula I, the cycloalkyl ketone has a structural formula of the following formula II, and the spiro compound has a structural formula of the following formula III: wherein n1 and n2 are each independently selected from 0, 1 or 2; R1 is selected from C3-C5 alkyl, R2 and R3 are each independently selected from hydrogen, nitro, cyano, carboxyl, C1-C5 alkyl, C2-C5 alkenyl, C1-C10 alkoxy, or R2 and R3 are bonded to each other to form a C3-C8 cycloalkyl, C5-C12 aryl, 3-12 membered heterocyclyl or 5-12 membered heteroaryl; R4 is selected from hydrogen, nitro, cyano, carboxyl, C1-C5 alkyl, C2-C5 alkenyl or C1-C10 alkoxy; The synthesis method comprises the following steps: Add diol and cycloalkyl ketone into an organic solvent, keep stirring, then add trifluoroacetic acid and a single atom catalyst; then heat and reflux for 2-5 hours to obtain the spiro compound.

[0018] In one aspect of the embodiments of the present disclosure, in the method for synthesizing a spirocyclic compound, the diol is selected from 1,4-butanediol, 1,3-propylene glycol or 1,5-pentanediol; the cycloalkyl ketone is selected from cyclohexanone, cycloheptanone, cyclopentanone, 1-benzocycloheptanone or 1-benzocyclohexanone.

[0019] In one aspect of the disclosed embodiments, in the synthesis method of the spirocyclic compound, the diol is selected from 1,4-butanediol, and the cycloalkyl ketone is selected from cyclohexanone. The synthesis method is as follows: In one aspect of the disclosed embodiments, in the synthesis method of the spirocyclic compound, the diol is selected from 1,4-butanediol, and the cycloalkyl ketone is selected from 1-benzocycloheptanone. The synthesis method is as follows: The technical solution provided by the embodiments of the present disclosure may have the following beneficial effects: It can be seen from the above embodiments that the present disclosure prepares a single-atom catalyst, which is a carbon-based material loaded with highly dispersed nickel single atoms, and can efficiently catalyze diols and cycloalkyl ketones to generate dioxaspiro compounds; and the carbon-based material loaded with highly dispersed nickel single atoms can further load cobalt atoms, thereby further increasing the yield of generating dioxaspiro compounds; the dioxaspiro compounds obtained by using the single-atom catalyst provided by the present disclosure can be applied to pharmaceutical small molecule intermediates. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0021] Figure 1 This is a spherical aberration electron microscope image of the single-atom catalyst prepared according to Example 1 of the present disclosure. DETAILED DESCRIPTION

[0022] The exemplary embodiments will be described in detail herein. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0023] In order to make the purpose, technical solution and advantages of the present disclosure clearer, the technical solution of the present disclosure will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. The relevant embodiments described herein are illustrative and are used to provide a basic understanding of the present disclosure. The embodiments of the present disclosure should not be interpreted as limiting the present disclosure.

[0024] For simplicity, the present disclosure only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, and any upper limit can be combined with any other upper limit to form an undefined range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an undefined range.

[0025] In the present disclosure, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further limitations, an element defined by the sentence "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0026] In the description of the present disclosure, unless otherwise specified, “above” and “below” include the present number.

[0027] Unless otherwise specified, the terms used in this disclosure have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this disclosure can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this disclosure).

[0028] The term "about" is used to describe and illustrate small changes. When used in conjunction with an event or situation, the term may refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very approximately. For example, when used in conjunction with a numerical value, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. In addition, amounts, ratios, and other numerical values ​​are sometimes presented in the present disclosure in a range format. It should be understood that such a range format is for convenience and simplicity, and should be flexibly understood to include not only numerical values ​​explicitly designated as range limits, but also all individual numerical values ​​or subranges encompassed within the range, as if each numerical value and subrange were explicitly designated.

[0029] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0030] In the present disclosure, the term "alkyl" refers to an aliphatic hydrocarbon group, which can be straight or branched. Branched refers to one or more lower alkyl groups connected to a linear alkyl chain, such as methyl, ethyl or propyl. For example, the term "C3-C12 alkyl" includes, but is not limited to: n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, etc.

[0031] In the present disclosure, the term "alkenyl" refers to an aliphatic hydrocarbon group, which contains at least one carbon-carbon double bond, which can be straight or branched, containing about 2 to about 15 carbon atoms in the chain, preferably alkenyl containing about 2 to about 12 carbon atoms in the chain, more preferably containing about 2 to about 6 carbon atoms in the chain. Branched refers to one or more lower alkyl groups connected to a linear alkenyl chain, such as methyl, ethyl or propyl. "Lower alkenyl" refers to a group containing about 2 to about 6 carbon atoms in the chain, which can be straight or branched. The term "substituted alkenyl" refers to an alkenyl group that can be substituted by one or more substituents, which can be the same or different, and each substituent is independently selected from halo, alkyl, aryl, cycloalkyl, cyano and alkoxy. Non-limiting examples of suitable alkenyls include vinyl, propenyl, n-butenyl, 3-methylbut-2-enyl, n-pentenyl, octenyl and decenyl.

[0032] In the present disclosure, the term "cycloalkyl" refers to a non-aromatic mono- or polycyclic ring system containing about 3 to about 8 carbon atoms, with preferred cycloalkyl rings containing about 5 to about 7 ring atoms. Non-limiting examples of suitable monocyclic cycloalkyls include cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like. Non-limiting examples of suitable polycyclic cycloalkyls include 1-decalinyl, norbornyl, adamantyl, and the like.

[0033] In the present disclosure, the term "aryl" refers to an aromatic monocyclic or polycyclic ring system. The aryl group may be optionally substituted with one or more "ring system substituents", which may be the same or different, and are as defined in the present disclosure. Non-limiting examples of suitable aryl groups include phenyl and naphthyl.

[0034] In the present disclosure, the term "heterocyclyl" refers to a non-aromatic saturated monocyclic or polycyclic ring system containing about 3 to about 10 ring atoms, preferably about 5 to about 10 ring atoms, wherein one or more of the ring atoms in the ring system is an element other than carbon, such as nitrogen, oxygen or sulfur, either alone or in combination. There are no adjacent oxygen and / or sulfur atoms in the ring system, and preferred heterocycles contain about 5 to about 6 ring atoms. The prefix aza, oxa or thia before the heterocyclyl root name indicates that at least one nitrogen, oxygen or sulfur atom, respectively, is present as a ring atom. Non-limiting examples of suitable monocyclic heterocyclyl rings include piperidinyl, pyrrolidinyl, piperazinyl, morpholinyl, thiomorpholinyl, thiazolidinyl, 1,3-dioxolanyl, 1,4-dioxacyclohexyl, tetrahydrofuranyl, tetrahydrophenylthio, tetrahydrothiopyranyl, and the like.

[0035] In this disclosure, the term "heteroaryl" refers to an aromatic monocyclic or polycyclic ring system containing about 5 to about 14 ring atoms, preferably about 5 to about 10 ring atoms, wherein one or more of the ring atoms is an element other than carbon, such as nitrogen, oxygen or sulfur, alone or in combination, with preferred heteroaryls containing about 5 to about 6 ring atoms. The prefix aza, oxa or thia before the heteroaryl root name means that at least one nitrogen, oxygen or sulfur atom, respectively, is present as a ring atom. The nitrogen atom of the heteroaryl group may be optionally oxidized to the corresponding N-oxide. Non-limiting examples of suitable heteroaryl groups include pyridinyl, pyrazinyl, furanyl, thiophenyl, pyrimidinyl, isoxazolyl, isothiazolyl, oxazolyl, thiazolyl, pyrazolyl, furazanyl, pyrrolyl, pyrazolyl, triazolyl, 1,2,4-thiadiazolyl, pyrazinyl, pyridazinyl, quinoxalinyl, 2,3-naphthyridinyl, imidazo[1,2-a]pyridinyl, imidazo[2,1-b]thiazolyl, benzofurazanyl, indolyl, azaindolyl, benzimidazolyl, benzothiophenyl, quinolinyl, imidazolyl, thienopyridinyl, quinazolinyl, thienopyrimidinyl, pyrrolopyridinyl, imidazopyridinyl, isoquinolinyl, benzazaindolyl, 1,2,4-triazinyl, benzothiazolyl, and the like.

[0036] In the present disclosure, the term "alkoxy" refers to -O-alkyl. Alkoxy can refer to a straight, branched or cyclic, saturated or unsaturated oxy-hydrocarbon chain, including, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy and pentoxy. Alkoxy can be optionally substituted with one or more alkoxy substituents. For example, the term "C1-C8 alkyl" includes, but is not limited to: methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy or n-hexoxy etc.

[0037] The present disclosure is further described below in conjunction with the examples. It should be understood that these examples are only used to illustrate the present disclosure and are not used to limit the scope of the present disclosure.

[0038] Embodiment 1 1. Preparation of single-atom nickel catalyst: 5 g of high-density carbon nanotubes (commercially available) were added to 100 mL of concentrated nitric acid, heated under reflux at 100 °C for 2 h, separated, washed, filtered, washed, and dried to obtain surface-oxidized carbon nanotubes; 0.1 g of nickel chloride was dissolved in water, and citric acid was added thereto to adjust the pH value to 3.3 to obtain a first mixed solution; then, carbon nanotubes with surface oxidation treatment were added thereto; the mixture was stirred for 4.5 hours, filtered and dried to obtain a solid; the obtained solid was placed in a tube furnace, heated to 600°C at a heating rate of 5°C / min in a nitrogen atmosphere, and baked for 6 hours, then naturally cooled to 300°C, the nitrogen was switched to a hydrogen-argon mixed gas, baked for 2.5 hours, and then naturally cooled to room temperature; then filtered, washed and dried to obtain a single-atom nickel catalyst, the spherical aberration electron microscope image of which is shown in FIG. Figure 1 shown.

[0039] 2. Preparation of 7,12-dioxaspiro[5.6]dodecane: 10 mmol of 1,4-butadiene and 10 mmol of cyclohexanone were added to 25 mL of acetone solution, and stirring was continued. Then, 1.5 mL of trifluoroacetic acid and 0.1 g of the single-atom nickel catalyst prepared above were added, nitrogen was introduced, and refluxed at 40° C. for 4 h. Then, the product 7,12-dioxaspiro[5.6]dodecane was obtained by extraction, column chromatography separation and purification, spin drying and freeze drying. The calculated yield was 72.5%. 1 H NMR: δ 1.37-1.86 (14H, 1.45 (dtt, J = 12.6, 6.6, 2.8Hz), 1.54 (dtdd, J = 13.0, 6.6, 2.8, 2.7 Hz), 1.68 (ddddd, J = 7.2, 6.7, 6.1,2.8, 1.5 Hz), 1.79 (ddd, J = 14.3, 6.6, 2.7 Hz)), 3.91 (4H, ddd, J = 14.4, 7.2,1.5 Hz).

[0040] Embodiment 2 1. Preparation of single-atom nickel catalyst: 5 g of high-density carbon nanotubes (commercially available) were added to 100 mL of concentrated nitric acid, heated under reflux at 100 °C for 2 h, separated, washed, filtered, washed, and dried to obtain surface-oxidized carbon nanotubes; 0.1 g of nickel chloride was dissolved in water, and citric acid was added thereto to adjust the pH value to 3.3 to obtain a first mixed solution; then, carbon nanotubes with surface oxidation treatment were added thereto; the mixture was stirred for 4.5 hours, filtered and dried to obtain a solid; the obtained solid was placed in a tubular furnace, and in a nitrogen atmosphere, the temperature was increased to 600°C at a heating rate of 5°C / min and calcined for 6 hours, then naturally cooled to 300°C, the nitrogen was switched to a hydrogen-argon mixed gas, calcined for 2.5 hours, and then naturally cooled to room temperature; then filtered, washed and dried to obtain a single-atom nickel catalyst.

[0041] 2. Preparation of 6,7,8,9-tetrahydrospiro[benzo[7]annulene-5,2'-[1,3]dioxepane]: 10 mmol of 1,4-butadiene and 10 mmol of 1-benzocycloheptanone were added to 25 mL of acetone solution, and stirring was continued. Then, 1.5 mL of trifluoroacetic acid and 0.1 g of the single-atom nickel catalyst prepared above were added, nitrogen was introduced, and refluxed at 40° C. for 4 h. Then, the product 6,7,8,9-tetrahydrospiro[benzo[7]annulene-5,2'-[1,3]dioxepane] was obtained by extraction, column chromatography separation and purification, spin drying and freeze drying. The calculated yield was 67.5%. 1 H NMR: δ 1.66 (4H, ddddd, J = 10.7, 7.3, 7.2, 2.3, 1.4 Hz), 1.77-2.01 (4H, 1.86 (ddddd, J = 13.3,6.9, 6.5, 3.1, 2.6 Hz), 1.92 (ddddd, J = 13.9, 7.3, 6.8, 2.9, 1.4 Hz)), 2.22(2H, ddd, J = 14.5, 6.9, 2.6 Hz), 2.75 (2H, ddd, J = 14.0, 7.3, 1.4 Hz), 3.84(4H, ddd, J = 9.7, 7.0, 2.5 Hz), 7.08-7.25 (3H, 7.14 (td, J = 7.8, 1.3 Hz), 7.18(ddd, J = 7.8, 1.3, 0.5 Hz), 7.19 (ddd, J = 7.9, 1.2, 0.5 Hz)), 7.32 (1H, td, J=7.8, 1.2 Hz).

[0042] Embodiment 3 1. Preparation of single-atom nickel / cobalt catalysts: 5 g of high-density carbon nanotubes (commercially available) were added to 100 mL of concentrated nitric acid, heated under reflux at 100 °C for 2 h, separated, washed, filtered, washed, and dried to obtain surface-oxidized carbon nanotubes; 0.1 g of nickel chloride and 0.1 g of cobalt chloride were dissolved in water, and citric acid was added thereto to adjust the pH value to 3.3 to obtain a first mixed solution; then, surface-oxidized carbon nanotubes were added thereto; the mixture was stirred for 4.5 h, filtered and dried to obtain a solid; the obtained solid was placed in a tubular furnace, and in a nitrogen atmosphere, the temperature was increased to 600 ° C at a heating rate of 5 ° C / min and calcined for 6 h, and then naturally cooled to 300 ° C, the nitrogen was switched to a hydrogen-argon mixed gas, calcined for 2.5 h, and then naturally cooled to room temperature; and then filtered, washed and dried to obtain a single-atom nickel / cobalt catalyst.

[0043] 2. Preparation of 7,12-dioxaspiro[5.6]dodecane: The steps of Example 3 are basically the same as those of Example 1, except that the yield of Example 3 is 79.8%.

[0044] Embodiment 4 1. Preparation of single-atom nickel / cobalt catalysts: The steps here in the fourth embodiment are the same as those in the third embodiment.

[0045] 2. Preparation of 6,7,8,9-tetrahydrospiro[benzo[7]annulene-5,2'-[1,3]dioxepane]: The steps of Example 4 are basically the same as those of Example 2, except that the yield of Example 4 is 75.2%.

[0046] Embodiment 5 1. Preparation of single-atom nickel / cobalt catalysts: The steps of Example 5 are basically the same as those of Example 3, except that the mass of cobalt chloride added in Example 5 is 0.2 g.

[0047] 2. Preparation of 7,12-dioxaspiro[5.6]dodecane: The steps of Example 5 are basically the same as those of Example 1, except that the yield of Example 5 is 76.3%.

[0048] Embodiment 6 1. Preparation of single-atom nickel / cobalt catalysts: The steps here in the sixth embodiment are the same as those in the fifth embodiment.

[0049] 2. Preparation of 6,7,8,9-tetrahydrospiro[benzo[7]annulene-5,2'-[1,3]dioxepane]: The steps of Example 6 are basically the same as those of Example 2, except that the yield of Example 6 is 72.1%.

[0050] Embodiment 7 1. Preparation of single-atom nickel / cobalt catalysts: The steps of Example 7 are basically the same as those of Example 3, except that the mass of cobalt chloride added in Example 7 is 0.01 g.

[0051] 2. Preparation of 7,12-dioxaspiro[5.6]dodecane: The steps of Example 7 are basically the same as those of Example 1, except that the yield of Example 7 is 85.6%.

[0052] Embodiment 8 1. Preparation of single-atom nickel / cobalt catalysts: The steps here in the eighth embodiment are the same as those in the seventh embodiment.

[0053] 2. Preparation of 6,7,8,9-tetrahydrospiro[benzo[7]annulene-5,2'-[1,3]dioxepane]: The steps of Example 8 are basically the same as those of Example 2, except that the yield of Example 8 is 80.5%.

[0054] Embodiment 9 1. Preparation of single-atom nickel / cobalt catalysts: The steps of Example 9 are basically the same as those of Example 3, except that the mass of cobalt chloride added in Example 9 is 0.02 g.

[0055] 2. Preparation of 7,12-dioxaspiro[5.6]dodecane: The steps of Example 9 are basically the same as those of Example 1, except that the yield of Example 7 is 91.4%.

[0056] Embodiment 10 1. Preparation of single-atom nickel / cobalt catalysts: The steps here of the tenth embodiment are the same as those of the ninth embodiment.

[0057] 2. Preparation of 6,7,8,9-tetrahydrospiro[benzo[7]annulene-5,2'-[1,3]dioxepane]: The steps of Example 10 are basically the same as those of Example 2, except that the yield of Example 10 is 86.2%.

[0058] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the disclosure disclosed herein. The present disclosure is intended to cover any variations, uses or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary technical means in the art that are not disclosed in the present disclosure.

Claims

1. A method for preparing a single-atom catalyst for synthesizing a spirocyclic compound from a diol and a cycloalkyl ketone, characterized in that: The reaction formula for synthesizing the spirocyclic compound from the diol and the cycloalkyl ketone is as follows: wherein n1 and n2 are each independently selected from 0, 1 or 2; R1 is selected from C3-C5 alkyl, R2 and R3 are each independently selected from hydrogen, nitro, cyano, carboxyl, C1-C5 alkyl, C2-C5 alkenyl, C1-C10 alkoxy, or R2 and R3 are bonded to each other to form a C3-C8 cycloalkyl, C5-C12 aryl, 3-12 membered heterocyclyl or 5-12 membered heteroaryl; R4 is selected from hydrogen, nitro, cyano, carboxyl, C1-C5 alkyl, C2-C5 alkenyl or C1-C10 alkoxy; The preparation method of the single atom catalyst comprises the following steps: Step 1: providing a carbon substrate, and pretreating the carbon substrate to obtain a carbon substrate having oxygen-containing groups on the surface; Step 2: dissolving nickel salt in water, adding citric acid thereto to adjust the pH value, to obtain a first mixed solution; Step 3: adding the carbon substrate having oxygen-containing groups on the surface to the first mixed solution, stirring for 3-5 hours, and then filtering and drying to obtain a first solid; Step 4: calcine the first solid in an inert gas atmosphere for 5-8 hours, and then calcine in a hydrogen-argon mixed atmosphere for 2-4 hours. After filtering, washing and drying, the single atom catalyst is obtained.

2. The method for preparing a single atom catalyst according to claim 1, characterized in that: The carbon substrate is selected from graphene, carbon nanotubes or activated carbon.

3. The method for preparing a single atom catalyst according to claim 1, characterized in that: In step 2, citric acid was added to adjust the pH to 3.0-3.

8.

4. The method for preparing a single atom catalyst according to claim 1, characterized in that: In step 2, while the nickel salt is dissolved in water, the cobalt salt is also added.

5. The method for preparing a single atom catalyst according to claim 4, characterized in that: In step 2, citric acid was added to adjust the pH to 3.2-3.

5.

6. The method for preparing a single atom catalyst according to claim 4, characterized in that: The ratio of the molar amount of the nickel element in the nickel salt to the molar amount of the cobalt element in the cobalt salt is selected from 1:(0.15-0.25).

7. The method for preparing a single atom catalyst according to any one of claims 1 to 6, characterized in that: The preparation method satisfies at least one of the following conditions: (1) In step 1, the pretreatment includes placing the carbon substrate in an acidic solution and heating it; (2) The mass ratio of the nickel salt to the carbon substrate having oxygen-containing groups on the surface is selected from (1.5-3.5): 100; (3) In step 4, the calcination temperature under an inert gas atmosphere is selected from 550° C. to 650° C.; (4) In step 4, the calcination temperature in the hydrogen-argon mixed gas atmosphere is selected from 250° C. to 350° C.; (5) The ratio of the molar amount of nickel in the nickel salt to the molar amount of cobalt in the cobalt salt is selected from 1:(0.18-0.22).

8. A single atom catalyst, characterized in that The single atom catalyst is prepared by the method for preparing the single atom catalyst according to any one of claims 1 to 7.

9. A method for synthesizing a spiro compound, characterized in that: The synthesis method uses diol and cycloalkyl ketone as raw materials; wherein the diol has the following structural formula I, the cycloalkyl ketone has the following structural formula II, and the spiro compound has the following structural formula III: wherein n1 and n2 are each independently selected from 0, 1 or 2; R1 is selected from C3-C5 alkyl, R2 and R3 are each independently selected from hydrogen, nitro, cyano, carboxyl, C1-C5 alkyl, C2-C5 alkenyl, C1-C10 alkoxy, or R2 and R3 are bonded to each other to form a C3-C8 cycloalkyl, C5-C12 aryl, 3-12 membered heterocyclyl or 5-12 membered heteroaryl; R4 is selected from hydrogen, nitro, cyano, carboxyl, C1-C5 alkyl, C2-C5 alkenyl or C1-C10 alkoxy; The synthesis method comprises the following steps: Add diol and cycloalkyl ketone to an organic solvent, keep stirring, then add trifluoroacetic acid, and the single-atom catalyst according to claim 8 or the single-atom catalyst prepared by the preparation method of the single-atom catalyst according to any one of claims 1 to 7; then heat and reflux for 2 to 5 hours to obtain the spiro compound.

10. The synthesis method according to claim 9, characterized in that The diol is selected from 1,4-butanediol, 1,3-propylene glycol or 1,5-pentanediol; the cycloalkyl ketone is selected from cyclohexanone, cycloheptanone, cyclopentanone, 1-benzocycloheptanone or 1-benzocyclohexanone.

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