A method for synthesizing a class of compounds with 1,4-dihydronaphthalene structure

Abstract

The present disclosure relates to a method for synthesizing a class of 1,4-dihydronaphthalene structure compounds represented by the following reaction formula (1). The method uses blue light to irradiate 2-naphthalene derivatives and N-heterocyclic carbene boranes in the presence of Ir(dF(CF3)ppy)2(dtbbpy)PF6, ethyl thioglycolate, and cesium carbonate to generate a photocatalytic reaction to obtain 1,4-dihydronaphthalene structure compounds. The synthetic method disclosed in the present disclosure is safe and simple to operate, has low cost, mild reaction conditions, and has a wide substrate range, providing a green, efficient, and safe approach for the synthesis of 1,4-dihydronaphthalene structure compounds.

Description

Technical Field

[0001] The present application belongs to the field of organic synthesis, and specifically relates to a method for synthesizing a class of compounds with a 1,4-dihydronaphthalene structure. Background Art

[0002] The 1,4-dihydronaphthalene skeleton is present in many natural products and is particularly common in the lignin family. They have high medicinal and economic value, but because the amount present in nature is very limited, effective methods for preparing such compounds are highly desired. However, the current synthesis methods for compounds with 1,4-dihydronaphthalene structures are very limited.

[0003] Mark D. Winemiller et al. (J. Am. Chem. Soc. 1998, 120, 7835-7840, DOI: 10.1021 / ja980624t) disclosed the following synthetic route of 1,4-dihydronaphthalene compounds:

[0004]

[0005] At room temperature, the naphthalene complex of pentaamineosmium(II) reacts with four different types of electrophiles to form a 1-naphthalene structure. The η3-allyl complex then reacts stereospecifically with a variety of nucleophiles to form a cis-1,4-dihydronaphthalene structure complex. After the nucleophilic addition, an oxidative decomposition complex is immediately carried out to directly separate the organic product. The total yield of the 1,4-dihydronaphthalene structure product obtained after chromatographic separation is usually in the range of 40-75%. However, the reaction conditions are harsh, the scope of application is narrow, and the cost is high.

[0006] Juntae Mo et al. (Organic Letters. 2010, 12, 2570-2573, DOI: 10.1021 / ol1007857) disclosed the following synthetic route of 1,4-dihydronaphthalene compounds:

[0007]

[0008] In the presence of 2.5 mol% PtCl2, ethyl 2-benzyl-2,3-butadienoate was synthesized using silver cocatalyst AgOT f , 1,4-dihydronaphthalene products were selectively synthesized in a 6-endo manner in a dichloromethane solvent at 80°C with a yield of 93%. However, this method has harsh reaction conditions, a narrow scope of application, and high cost.

[0009] Therefore, there is still a need to develop a novel synthesis method for compounds with 1,4-dihydronaphthalene structure. Summary of the invention

[0010] In view of the shortcomings of the above-mentioned prior art, one object of the present application is to provide a method for synthesizing a class of compounds with a 1,4-dihydronaphthalene structure, wherein the method adopts a photocatalytic hydrogen atom transfer strategy to react N-heterocyclic carbene borane with a naphthalene ring, and finally obtains a compound with a 1,4-dihydronaphthalene structure. The synthesis method has mild conditions, does not require dangerous reagents such as strong acids and strong bases, and has a high yield.

[0011] In order to achieve the above object, the present disclosure provides a method for synthesizing a class of compounds having a 1,4-dihydronaphthalene structure represented by the following reaction formula (1), wherein the synthesis method is carried out as follows:

[0012]

[0013] In the presence of Ir(dF(CF3)ppy)2(dtbbpy)PF6, ethyl thioglycolate, and cesium carbonate, 2-naphthalene derivatives were irradiated with blue light. and N-heterocyclic carbene boranes A photocatalytic reaction occurs to obtain a compound with a 1,4-dihydronaphthalene structure.

[0014] The substituent R1 is selected from amide, cyano, -C(=O)O-C1-C6 alkyl, -C(=O)-C1-C6 alkyl.

[0015] R2 is selected from C1-C4 alkyl, C6-C10 aryl.

[0016] R3 is selected from C1-C3 alkyl.

[0017] Preferably, the substituent R1 is selected from amide, cyano, -C(=O)O-C1-C3 alkyl, -C(=O)-C1-C3 alkyl.

[0018] More preferably, the substituent R1 is selected from -C(=O)OCH3, -C(=O)OC2H5, -C(=O)OC3H7, -C(=O)Otert-butyl, -C(=O)methyl, C(=O)NH2, -CN.

[0019] Preferably, the substituent R2 is selected from methyl, ethyl, propyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, benzyl.

[0020] Preferably, the substituent R3 is selected from methyl, ethyl, propyl, n-propyl, isopropyl.

[0021] In a feasible embodiment, in the method for synthesizing the compound with 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of N-heterocyclic carbene borane is 1.45 to 1.55, preferably 1.49 to 1.51.

[0022] In a feasible embodiment, in the synthesis method of the compound with 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of Ir(dF(CF3)ppy)2(dtbbpy)PF6 is 0.0090 to 0.0110, preferably 0.0099 to 0.0111.

[0023] In a feasible embodiment, in the synthesis method of the compound with 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of ethyl mercaptoacetate is 0.15 to 0.25, preferably 0.19 to 0.21, and the yield will be reduced if it is out of this range.

[0024] In a feasible embodiment, in the method for synthesizing the compound with 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of cesium carbonate is 0.4 to 0.6, preferably 0.49 to 0.51.

[0025] In a feasible implementation, the time of the photocatalytic reaction in the synthesis method of the compound with 1,4-dihydronaphthalene structure is 18 to 30 hours, preferably 24 hours.

[0026] In a feasible embodiment, the temperature of the photocatalytic reaction in the synthesis method of the compound with 1,4-dihydronaphthalene structure is 25°C to 45°C, preferably 40°C.

[0027] In a feasible implementation, the photocatalytic reaction in the method for synthesizing the compound having a 1,4-dihydronaphthalene structure is carried out under the condition of isolating oxygen and moisture.

[0028] In a feasible implementation manner, in the method for synthesizing the compound with 1,4-dihydronaphthalene structure, the wavelength of the blue light is 420nm to 480nm.

[0029] In a feasible implementation, in the method for synthesizing the compound with 1,4-dihydronaphthalene structure, the light intensity of the blue light is 0.8 cd to 1.0 cd.

[0030] In a feasible embodiment, the photocatalytic reaction can be carried out in the presence of a solvent, and the solvent is selected from one of acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide and N,N-dimethylacetamide.

[0031] The technical solution provided by the present disclosure has at least the following beneficial effects compared with the prior art:

[0032] The synthesis method of 1,4-dihydronaphthalene disclosed in the present invention adopts a visible light catalytic strategy, directly uses 2-naphthalene derivatives and N-heterocyclic carbene boranes as raw materials, is safe and simple to operate, has low cost, mild reaction conditions, and has a wide substrate range, providing a green, efficient and safe way for the synthesis of 1,4-dihydronaphthalene structural compounds. DETAILED DESCRIPTION

[0033] Hereinafter, the present invention will be described in detail. Before describing, it should be understood that the terms used in this specification and the appended claims should not be interpreted as being limited to the general meaning and dictionary meaning, but should be interpreted according to the meaning and concept corresponding to the technical aspects of the present invention on the basis of the principle that the inventor is allowed to appropriately define the terms for the best interpretation. Therefore, the descriptions presented here are only preferred examples for illustrative purposes and are not intended to limit the scope of the present invention, so that it should be understood that other equivalents or improvements can be obtained therefrom without departing from the spirit and scope of the present invention.

[0034] As used herein, the terms "include", "comprising", "having", "containing" or any other similar terms are open-ended transitional phrases, which are intended to cover non-exclusive inclusions. For example, a composition or article containing multiple elements is not limited to the elements listed herein, but may also include other elements that are not explicitly listed but are generally inherent to the composition or article. In addition, unless otherwise expressly stated, the term "or" refers to an inclusive "or" rather than an exclusive "or". For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). In addition, as used herein, the terms "include", "comprising", "having", and "containing" should be interpreted as having been specifically disclosed and simultaneously covering closed or semi-closed transitional phrases such as "consisting of" and "consisting essentially of".

[0035] In the prior art, the synthesis of 1,4-dihydronaphthalene compounds usually uses highly active reagents, highly dangerous reagents, transition metals, and harsh reaction conditions, which leads to poor process safety, narrow scope of application, and high cost. In response to these problems, the present disclosure provides a method for synthesizing a class of compounds with 1,4-dihydronaphthalene structures, which adopts a strategy of photocatalytic hydrogen atom transfer to react N-heterocyclic carbene borane with a naphthalene derivative to finally obtain 1,4-dihydronaphthalene. The synthesis method has mild conditions, does not require dangerous reagents such as strong acids and strong bases, and has a high yield.

[0036] In order to achieve the above objectives, in a first aspect, the present application provides a method for synthesizing 1,4-dihydronaphthalene, and the synthesis method is carried out as follows:

[0037]

[0038] In the presence of Ir(dF(CF3)ppy)2(dtbbpy)PF6, ethyl thioglycolate, and cesium carbonate, 2-naphthalene derivatives were irradiated with blue light. and N-heterocyclic carbene boranes A photocatalytic reaction occurs to obtain a compound with a 1,4-dihydronaphthalene structure.

[0039] The chemical name of the Ir(dF(CF3)ppy)2(dtbbpy)PF6 is [4,4'-bis(1,1-dimethylethyl)-2,2'-bipyridine N1,N1']bis[3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridyl N]phenyl-C] iridium (III) hexafluorophosphate, CAS No.: 870987-63-6, which is an excellent photocatalyst. The CAS No. of the thiol: ethyl mercaptoacetate: 623-51-8, is a hydrogen atom transfer catalyst. The cesium carbonate is an additive that can provide an alkaline reaction environment. By combining the above-mentioned compounds, the photocatalytic reaction can be fully promoted to obtain 1,4-dihydronaphthalene products.

[0040] In addition, the 2-naphthalene derivative refers to a naphthalene formed by 2 benzene rings sharing 2 adjacent carbon atoms, and has a substituent R1 at the carbon 2 position, and the substituent R1 can be selected from amide, cyano, -C(=O)O-C1-C6 alkyl, -C(=O)-C1-C6 alkyl. Preferably, the substituent R1 is selected from amide, cyano, -C(=O)O-C1-C3 alkyl, -C(=O)-C1-C3 alkyl. More preferably, the substituent R1 is selected from -C(=O)OCH3, -C(=O)OC2H5, -C(=O)OC3H7, -C(=O)O tert-butyl, -C(=O)methyl, C(=O)NH2, -CN.

[0041] In a feasible embodiment, in the synthesis method of the compound of 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of N-heterocyclic carbene borane is 1.45-1.55, preferably 1.49-1.51. For example, the molar amount of N-heterocyclic carbene borane can be 1.46, 1.47, 1.48, 1.49, 1.50, 1.51, 1.52, 1.53, 1.54, 1.55. If it is less than this range, the yield of the product will be reduced, and if it is greater than this range, the N-heterocyclic carbene borane will be wasted.

[0042] In a feasible embodiment, in the synthesis method of the compound with 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of Ir(dF(CF3)ppy)2(dtbbpy)PF6 is 0.0090~0.0110, preferably 0.0099 to 0.0111. A molar amount below this range will reduce the yield, and a molar amount above this range will result in waste of Ir(dF(CF3)ppy)2(dtbbpy)PF6.

[0043] In a feasible embodiment, in the synthesis method of the compound of 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of ethyl mercaptoacetate is 0.15 to 0.25, preferably 0.19 to 0.21, for example, the molar amount of ethyl mercaptoacetate can be 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, and the yield will be reduced if it is not within this range.

[0044] In a feasible embodiment, in the synthesis method of the compound of 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of cesium carbonate is 0.4 to 0.6, preferably 0.49 to 0.51, for example, the molar amount of cesium carbonate can be 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, and the yield will be reduced if it is not within this range.

[0045] The halogen is selected from F, Cl, Br and I.

[0046] In a feasible embodiment, the photocatalytic reaction time is 18 to 30 hours (for example, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours or 30 hours, or any other specific value in the range), preferably 24 hours. In the present disclosure, if the reaction time of the photocatalytic reaction is too long, side reactions may occur, and if the reaction time is too short, the yield will be reduced.

[0047] In a feasible embodiment, the temperature of the photocatalytic reaction is 25°C to 45°C, that is, within the room temperature range (for example, it can be 25°C, 27°C, 29°C, 31°C, 33°C, 35°C, 37°C, 41°C, 33°C or 45°C, or any other specific value in the range), preferably 40°C. In the present disclosure, too high a temperature of the photocatalytic reaction will lead to the occurrence of side reactions, and too low a temperature will reduce the reaction rate, resulting in a decrease in yield. In addition, the temperature conditions of the photocatalytic reaction are very mild, around room temperature, and no strong regulation is required, which is green and energy-saving.

[0048] In a feasible embodiment, the photocatalytic reaction is carried out under the condition of isolating oxygen and moisture. In the synthesis method disclosed in the present invention, active substances such as oxygen or moisture will inactivate the catalytic components and affect the reaction, so they should be isolated. Therefore, the photocatalytic reaction disclosed in the present invention can be carried out under the protection of an inert gas (such as nitrogen). In addition, the container of the photocatalytic reaction is not particularly limited, as long as it can meet the reaction requirements and isolate oxygen and moisture. For example, a laboratory can use a Schlenk bottle to carry out the reaction, but the present disclosure is not limited to this.

[0049] In a feasible implementation, the wavelength of the blue light is 420 nm to 480 nm. Within the wavelength range, the electron transition and transfer of Ir(dF(CF3)ppy)2(dtbbpy)PF6 can be promoted to achieve the photocatalysis.

[0050] In a feasible implementation, the light intensity of the blue light is 0.8 cd to 1.0 cd. Within the light intensity range, sufficient light energy can be continuously provided to the reaction system to promote the reaction to proceed fully.

[0051] In addition, the light source of the blue light is not particularly limited, as long as it can provide light radiation of the required wavelength and intensity. However, from the perspective of energy saving and environmental protection, the light source is preferably an LED light source.

[0052] The following examples are only listed as examples of embodiments of the present invention and do not constitute any limitation to the present invention. It can be understood by those skilled in the art that modifications within the scope of the essence and concept of the present invention fall within the scope of protection of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

[0053] Example

[0054] Material Source

[0055] Ir(dF(CF3)ppy)2(dtbbpy)PF6, according to the literature Jeffrey W.Johannes et al., "PracticalSyntheses of[2,2′-bipyridine]bis[3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridinyl]phenyl]iridium(III)hexafluorophosphate,[Ir{dF(CF3)ppy}2(bpy)]PF6 and[4,4′-bis(tert-butyl)-2,2′-bipyridine]bis[3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridinyl]phenyl]iridium(III )hexafluorophosphate,[Ir{dF(CF3)ppy}2(dtbbpy)]PF6”, Org.Synth.2017,94,77-92(DOI:10.15227 / orgsyn.094.0077) synthesized this compound;

[0056] Methyl 2-naphthoate, purity 98%, purchased from Anhui Zesheng Technology Co., Ltd.;

[0057] 2-acetonapthone, purity 98%, purchased from Anhui Zesheng Technology Co., Ltd.;

[0058] Naphthalene-2-carbonitrile, purity 97%, purchased from Anhui Zesheng Technology Co., Ltd.;

[0059] Naphthalene-2-carboxamide, purity 97%, purchased from Anhui Zesheng Technology Co., Ltd.;

[0060] Ethyl mercaptoacetate, purity 99%, purchased from Shanghai Titan Technology Co., Ltd.;

[0061] Cesium carbonate, purity 99.9%, purchased from Anhui Zesheng Technology Co., Ltd.;

[0062] Embodiment 1:

[0063]

[0064] Ir(dF(CF3)ppy)2(dtbbpy)PF6 (1.2 mg, 0.001 mmol), methyl 2-naphthoate (18.6 mg, 0.1 mmol, 1.0 equiv), N,N-dimethylimidazol-2-ylideneborane (16.5 mg, 0.15 mmol, 1.5 equiv) and cesium carbonate (16.3 mg, 0.05 mmol) were added to a Schlenk bottle. Under nitrogen protection, ethyl thioglycolate (2.2 μL, 0.02 mmol, 20 mol%) and CH3CN (2 mL) were added. The solution was degassed to remove oxygen from the solvent. After completion, the solution was light yellow. The Schlenk bottle was placed under a 420-480 nm blue LED light source (18 W, 0.8-1.0 cd) and stirred in an oil bath (40°C) for 24 h. After the reaction, the solution was orange. The product was separated by silica gel column chromatography (mobile phase: petroleum ether:ethyl acetate=6:1-2:1) to obtain a colorless oily product with a yield of 76%. 1 H NMR (400MHz, CDCl3): δ7.01–6.92(m,3H),6.77–6.71(m,3H),6.62(dd,J=5.4,3.5Hz ,1H),3.72(s,3H),3.44–3.39(m,7H),3.32(d,J=6.1Hz,1H),3.16(d,J=20.4Hz,1H); 11 B NMR (128MHz, CDCl3) δ-25.60 (t, J=91.9Hz); 13 C NMR (100 MHz, CDCl3) δ 168.22, 146.92, 139.94, 131.60, 129.42, 127.08, 125.92, 125.44, 123.12, 120.21, 51.34, 35.60, 31.20; HRMS (EI): calculated value C 17 H 21 BN2O2Na[M+Na] + 319.1668, measured value 319.1672.

[0065] Embodiment 2:

[0066]

[0067] Ir(dF(CF3)ppy)2(dtbbpy)PF6 (1.2 mg, 0.001 mmol), naphthalene-2-carbonitrile (15.3 mg, 0.1 mmol, 1.0 equiv), N,N-diisopropylimidazol-2-ylideneborane (16.5 mg, 0.15 mmol, 1.5 equiv) and cesium carbonate (16.3 mg, 0.05 mmol) were added to a Schlenk bottle. Under nitrogen protection, ethyl thioglycolate (2.2 μL, 0.02 mmol, 20 mol%) and CH3CN (2 mL) were added. The solution was degassed to remove oxygen from the solvent. After completion, the solution was light yellow. The Schlenk bottle was placed under a 420-480 nm blue LED light source (18 W, 0.8-1.0 cd) and stirred in an oil bath (40°C) for 24 h. After the reaction was completed, the solution was orange in color. The product was separated by silica gel column chromatography (mobile phase: petroleum ether:ethyl acetate=6:1-2;1) to obtain a colorless oily product with a yield of 65%. 1 H NMR (400MHz, CDCl3): δ7.02–6.93(m,5H),6.68–6.64(m,1H),6.43–6.38(m,1H),4.90–4.79(m,2H),3.36–

[0068] 3.29(m,2H),3.00(s,1H),1.31(d,J=6.7Hz,6H),1.24(d,J=6.8Hz,6H). 11 B NMR (128MHz, CDCl3): δ-25.56 (t, J=91.2Hz); 13 C NMR (100 MHz, CDCl3): δ 144.44, 134.20, 129.84, 127.48, 125.76 (d, J = 8.0 Hz), 123.87, 122.49, 120.64, 115.65, 49.36, 30.99, 23.07, 22.75; HRMS (EI): calculated value C 20 H 26 BN3Na[M+Na] + 342.2117, measured value 342.2119.

[0069] Embodiment 3:

[0070]

[0071] Ir(dF(CF3)ppy)2(dtbbpy)PF6 (1.2 mg, 0.001 mmol), naphthalene-2-carboxamide (17.1 mg, 0.1 mmol, 1.0 equiv), N-propylimidazol-2-ylideneborane (16.5 mg, 0.15 mmol, 1.5 equiv) and cesium carbonate (16.3 mg, 0.05 mmol) were added to a Schlenk bottle. Under nitrogen protection, ethyl thioglycolate (2.2 μL, 0.02 mmol, 20 mol%) and CH3CN (2 mL) were added. The solution was degassed to remove oxygen from the solvent. After completion, the solution was light yellow. The Schlenk bottle was placed under a 420-480 nm blue LED light source (18 W, 0.8-1.0 cd) and stirred in an oil bath (40°C) for 24 h. After the reaction was completed, the solution was orange in color. The product was separated by silica gel column chromatography (mobile phase: petroleum ether:ethyl acetate=6:1-2;1) to obtain a colorless oily product with a yield of 60%. 1 H NMR (400MHz, CDCl3): δ7.00–6.85(m,4H),6.76(s,1H),6.72(s,1H),6.58–6.52(m,1H),5.73(s,1H),3.56–3.44(m,2 H),3.26–3.19(m,2H),3.16(s,3H),3.10–2.83(m,1H),2.45(d,J=20.6Hz,1H),1.62–1.48(m,2H),0.83–0.75(m,3H); 11 BNMR (128MHz, CDCl3): δ-24.83 (t, J=89.5Hz); 13 C NMR (100 MHz, CDCl3): δ 170.90, 146.07, 141.00, 131.59, 127.01, 126.95, 126.89, 125.65, 123.35, 120.71, 118.80, 49.67, 35.39, 30.52, 23.37, 10.85; HRMS (EI): calculated

[0072] C 18 H 24 BN3ONa[M+Na] + 332.2098, measured value 332.2032.

[0073] Embodiment 4:

[0074]

[0075] Ir(dF(CF3)ppy)2(dtbbpy)PF6 (1.2 mg, 0.001 mmol), 2,6-naphthalene dimethyl ester (24.4 mg, 0.1 mmol, 1.0 equiv), N,N-diisopropylimidazol-2-ylidene borane (16.5 mg, 0.15 mmol, 1.5 equiv) and cesium carbonate (16.3 mg, 0.05 mmol) were added to a Schlenk bottle. Under nitrogen protection, ethyl thioglycolate (2.2 μL, 0.02 mmol, 20 mol%) and CH3CN (2 mL) were added. The solution was degassed to remove oxygen from the solvent. After completion, the solution was light yellow. The Schlenk bottle was placed under a 420-480 nm blue LED light source (18 W, 0.8-1.0 cd) and stirred in an oil bath (40°C) for 24 h. After the reaction was completed, the solution was orange in color. The product was separated by silica gel column chromatography (mobile phase: petroleum ether:ethyl acetate=6:1-2:1) to obtain a colorless oily product with a yield of 77%. 1 H NMR (400MHz, CDCl3): δ7.70(s,1H),7.62(dd,J=8.1,1.8Hz,1H),6.77(s,2H),6.76–6.72(m,1H),6.65(d, J=8.0Hz,1H),3.86(s,3H),3.71(s,3H),3.50–3.45(m,1H),3.41(s,6H),3.41–3.35(m,1H),3.22(s,1H); 11 B NMR (128MHz, CDCl3): δ-25.58 (t, J=91.0Hz); 13 C NMR (100 MHz, CDCl3): δ 167.81, 167.71, 153.65, 139.17, 131.78, 129.02, 128.53, 126.90, 125.71, 124.90, 120.35, 51.70, 51.38, 35.66, 31.06; HRMS (EI): calculated value C 19 H 23 BN2O4Na[M+Na] + 377.1649, measured value 377.1653.

[0076] Comparative Examples 1-8:

[0077]

[0078] Except for the conditions shown in Table 1 below, the photocatalytic experiment was carried out in the same manner as in Example 1, and the yields are also shown in Table 1.

[0079] [Table 1]

[0080]

[0081] In Table 1, the yields are as follows: 1,3,5-trimethoxybenzene is used as the internal standard. 1 The yield was determined by H-NMR.

[0082] From the results in Table 1 above, it can be seen that in the absence of light, photocatalyst, and ethyl thioglycolate, the target product is not obtained, and in the absence of a base, the yield is reduced to 50%. When the photocatalyst is other Ir-type photocatalysts, such as Ir(ppy)3 and Ir(ppy)2(dtbbpy)PF6, no product is generated. When the mercaptan is other mercaptan, such as methyl thioglycolate, the product yield is reduced. When the base is other bases, such as potassium carbonate, the product yield is reduced and the chemical selectivity is deteriorated.

[0083] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for synthesizing a type of 1,4-dihydronaphthalene structure compound represented by the following reaction formula (1), the synthesis method being carried out as follows: In the presence of Ir(dF(CF3)ppy)2(dtbbpy)PF6, ethyl thioglycolate, and cesium carbonate, 2-naphthalene derivatives were irradiated with blue light. and N-heterocyclic carbene boranes A photocatalytic reaction occurs to obtain a compound with a 1,4-dihydronaphthalene structure; wherein the substituent R1 is selected from amide, cyano, -C(=O)O-C1-C6 alkyl, -C(=O)-C1-C6 alkyl; R2 is selected from C1-C4 alkyl, C6-C10 aryl, benzyl; R3 is selected from C1-C3 alkyl; The photocatalytic reaction is carried out in the presence of a solvent, and the solvent is selected from one of acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide and N,N-dimethylacetamide.

2. The synthesis method according to claim 1, characterized in that The substituent R1 is selected from amide, cyano, -C(=O)O-C1-C3 alkyl, -C(=O)-C1-C3 alkyl; The substituent R2 is selected from methyl, ethyl, propyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, benzyl; The substituent R3 is selected from methyl, ethyl, propyl, n-propyl and isopropyl.

3. The synthesis method according to claim 1, characterized in that The substituent R1 is selected from -C(=O)OCH3, -C(=O)OC2H5, -C(=O)OC3H7, -C(=O)Otert-butyl, -C(=O)methyl, C(=O)NH2, -CN.

4. The synthesis method according to claim 1, characterized in that In the synthesis method, based on 1 mole of the 2-naphthalene derivative, the molar amount of the N-heterocyclic carbene borane is 1.45 to 1.

55.

5. The synthesis method according to claim 1, characterized in that In the synthesis method, based on 1 mole of the 2-naphthalene derivative, the molar amount of the N-heterocyclic carbene borane is 1.49 to 1.

51.

6. The synthesis method according to claim 1, characterized in that In the synthesis method of the compound with 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of Ir(dF(CF3)ppy)2(dtbbpy)PF6 is 0.0090 to 0.0110.

7. The synthesis method according to claim 1, characterized in that In the synthesis method of the compound with 1,4-dihydronaphthalene structure, based on 1 mole of 2-naphthalene derivative, the molar amount of Ir(dF(CF3)ppy)2(dtbbpy)PF6 is 0.0099 to 0.0110.

8. The synthesis method according to claim 1, characterized in that In the synthesis method, the molar amount of ethyl thioglycolate is 0.15 to 0.25 based on 1 mole of the 2-naphthalene derivative.

9. The synthesis method according to claim 1, characterized in that In the synthesis method, the molar amount of ethyl thioglycolate is 0.19 to 0.21 based on 1 mole of the 2-naphthalene derivative.

10. The synthesis method according to claim 1, characterized in that In the synthesis method, the molar amount of cesium carbonate is 0.4 to 0.6 based on 1 mole of the 2-naphthalene derivative.

11. The synthesis method according to claim 1, characterized in that: In the synthesis method, the molar amount of cesium carbonate is 0.49 to 0.51 based on 1 mole of the 2-naphthalene derivative.

12. The synthesis method according to claim 1, characterized in that: In the synthesis method, the photocatalytic reaction time is 18 to 30 hours; the photocatalytic reaction temperature is 25° C. to 45° C.

13. The synthesis method according to claim 1, characterized in that: In the synthesis method, the photocatalytic reaction time is 24 hours; the photocatalytic reaction temperature is 40°C.

14. The synthesis method according to claim 1, characterized in that In the synthesis method, the photocatalytic reaction is carried out under the condition of isolating oxygen and moisture.

15. The synthesis method according to claim 1, characterized in that: In the synthesis method, the wavelength of the blue light is 420nm to 480nm, and the light intensity is 0.8cd to 1.0cd.

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