A preparation method of N,O-boron difluoride complex

Abstract

The present invention discloses a method for preparing an N,O-boron difluoride complex. The method uses a pyridine acetylene compound represented by formula (1) as a raw material and tetrafluoroboric acid or boron trifluoride etherate as a boron source, and reacts in a solvent to produce the N,O-boron difluoride complex represented by formula (2). The preparation method of the present invention features a simple and mature raw material synthesis process, mild reaction conditions, no need for the addition of a catalyst, simple operation, and excellent yield, providing a new, efficient, and low-cost approach for preparing N,O-boron difluoride complexes. #imgabs0#

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and more particularly to a method for preparing an N,O-boron difluoride complex. Background Art

[0002] N,O-boron difluoride complexes are a type of tetracoordinate boron compound. When the boron atom with an empty P orbital is coordinated with an electron-rich chelating ligand and a fluorine atom, the boron center assumes a typical tetrahedral configuration. This increases electron delocalization, forming a rigid π-conjugated skeleton that inhibits energy loss caused by molecular vibrations, thereby improving the compound's luminescence efficiency. Furthermore, the chelated complex alters the compound's electronic structure, lowering the LUMO energy level and enhancing its electron affinity.

[0003]

[0004] Currently, there is little research on the preparation methods of N,O-boron difluoride complexes in the existing technology. The main methods are: (1) reaction of N,O bidentate ligands with boron trifluoride ether complex or silver tetrafluoroborate (Journal of Organometallic Chemistry, 2013, vol. 743, p. 1-9). The disadvantage is that raw materials containing N and O atoms need to be prepared in advance as ligands.

[0005]

[0006] (2) The pyridine compound is activated by metal-catalyzed carbon-hydrogenation to obtain an intermediate metal-coordinated N,O bidentate ligand, which is then reacted with silver tetrafluoroborate (Angewandte Chemie-International Edition, 2020, vol. 59, #48, p. 21541-21545). The disadvantage is that a metal is required as a catalyst, and silver tetrafluoroborate is relatively expensive as a boron source.

[0007] Summary of the Invention

[0008] The present invention overcomes the defects of the prior art such as difficulty in raw material synthesis, complex reaction conditions and low yield, and provides a method for preparing an N,O-boron difluoride complex. The method has a simple and mature raw material synthesis process, does not require a catalyst, is simple to operate, has an excellent yield, and has prospects for industrial production.

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] The pyridine acetylene compound represented by formula (1) is used as a raw material, tetrafluoroboric acid or boron trifluoride ether is used as a boron source, and a reaction is carried out in a solvent to prepare the N,O-boron difluoride complex represented by formula (2). The reaction formula is as follows:

[0011]

[0012] Among them, R 1 is C1-C6 alkyl, C1-C6 alkoxy, halogen, cyano, nitro, hydroxyl or C1-C4 ester; R 2 It is a substituted or unsubstituted C6-C14 aryl group; or a C4-C10 heteroaryl group, wherein the substitution is by one or more of C1-C4 alkyl, C1-C4 alkoxy, halogen or N,N-diphenylamino. When the substitution is at multiple sites, the substituents in the substitution are the same or different.

[0013] Preferably, R 1 is a C1-C6 alkyl group, a C1-C4 alkoxy group, a halogen group, a cyano group, a nitro group, a hydroxyl group or a C1-C4 ester group.

[0014] Preferably, R 2 It is a substituted or unsubstituted C6-C12 aryl group or C4-C8 heteroaryl group.

[0015] More preferably, R 2 is phenyl, naphthyl or thienyl.

[0016] Substituent Definitions and General Terms

[0017] The term "alkyl" used in the present invention refers to a saturated, linear, branched or cyclic monovalent hydrocarbon group containing 1 to 6 carbon atoms.

[0018] As used herein, the term "aryl" refers to monocyclic, bicyclic, and tricyclic carbon ring systems containing 6-14 ring atoms, 6-12 ring atoms, or 6-10 ring atoms, wherein at least one ring system is aromatic, wherein each ring system comprises a ring of 3-7 atoms and has one or more points of attachment to the rest of the molecule. The term "aryl" can be used interchangeably with the term "aromatic ring." Examples of aryl groups include phenyl, indenyl, naphthyl, phenanthrene, and anthracene, among others.

[0019] The term "heteroaryl" refers to monocyclic, bicyclic, and tricyclic ring systems containing 5-10 ring atoms, or 5-6 ring atoms, wherein at least one ring system is aromatic and at least one ring system contains one or more heteroatoms, wherein each ring system contains 5-7 ring atoms and has one or more points of attachment to the rest of the molecule. The term "heteroaryl" can be used interchangeably with the terms "heteroaromatic ring" or "heteroaromatic compound." Examples of heteroaryl groups include, but are not limited to, 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, N-imidazolyl, 2-imidazolyl, 4-imidazolyl, 5-imidazolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 2-oxazolyl, 4-oxazolyl, 5-oxazolyl, N-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-pyrimidinyl, 4-pyrimidinyl, 5-pyrimidinyl, and the like.

[0020] The term "alkoxy" means an alkyl group attached to the rest of the molecule via an oxygen atom, wherein the alkyl group has the meaning as defined herein.

[0021] The term "halogen" as used herein refers to fluorine, chlorine, bromine, and iodine.

[0022] Preferably, the molar ratio of the pyridine acetylene compound represented by formula (1) to the boron source is 1:1-10.

[0023] More preferably, the molar ratio of the pyridine acetylene compound represented by formula (1) to the boron source is 1:2-5.

[0024] Preferably, the solvent is one or more of toluene, fluorobenzene, nitrobenzene, trifluorotoluene or water.

[0025] Preferably, the reaction temperature is 80-150°C.

[0026] More preferably, the reaction temperature is 110-120°C.

[0027] Preferably, the reaction time is 24 to 48 hours.

[0028] More preferably, the reaction time is 30 to 40 hours.

[0029] The pyridine acetylene compound of formula (1) of the present invention can be purchased directly or prepared by referring to known literature methods. As an embodiment, it can be prepared according to the following two methods: ① reacting a halogenated pyridine compound of formula S1 with an alkynyl compound of formula S2 to obtain the pyridine acetylene compound of formula (1) (Applied Organometallic Chemistry, 2015, vol. 29, #12, p. 846-849); ② reacting a 2-ethynyl pyridine compound of formula S3 with a compound of formula S4 to obtain the pyridine acetylene compound of formula (1) (Beilstein Journal of Organic Chemistry, 2016, vol. 12, p. 2005-2011). Wherein X represents a halogen.

[0030]

[0031] Furthermore, a series of N,O-boron difluoride complexes can be prepared by the above preparation method, some of which are listed below:

[0032]

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The preparation method of the invention has simple and mature raw material synthesis process, mild reaction conditions, no need to add catalyst, simple process operation, and excellent yield, providing a new, efficient and low-cost way to prepare N,O-boron difluoride complex. DETAILED DESCRIPTION

[0035] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art and can be directly purchased or synthesized by known literature methods.

[0036] Example 1

[0037] This example provides a method for preparing 1-phenyl-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2a), the steps of which are as follows:

[0038]

[0039] 2-(Phenylacetyl)pyridine (42 mg, 0.2 mmol, 1.0 eq.), toluene (2 mL), and HBF4 (48 wt% aqueous solution, 8 mmol, 4.0 eq.) were added to the reaction flask in sequence. The mixture was stirred at 110°C for 48 hours. After completion of the reaction, the mixture was filtered, the solvent was removed using a rotary evaporator, and the mixture was purified by column chromatography using petroleum ether and ethyl acetate (PE / EA = 3 / 1) as eluents to obtain 1-phenyl-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2a, 32 mg, 65%).

[0040] 1 H NMR (500MHz, CDCl3) δ8.36(d,J=5.5Hz,1H),7.89–7.85(m,2H),7.85–7.80(m,1H),7.37(d,J=7.1Hz,3H),7.22(dd,J=16.5,7.6Hz,2H),6.31(s,1H). 13 C NMR (126MHz, CDCl3) δ163.0,151.8,141.2,139.9,134.2,131.0,128.5,126.5,122.4,120.2,93.1. 19 FNMR(471MHz,CDCl3)δ-140.81,-140.84,-140.88,-140.91.IR(KBr,cm -1 ):3448,3172,2359,1634,1492,1400,1295,1088,992,853,765,526.

[0041] Examples 2 to 11

[0042] This example provides a series of preparation methods for N,O-boron difluoride complexes. The preparation methods and raw materials are the same as those in Example 1. Different boron sources and solvents are used to prepare 1-phenyl-2-(pyridin-2-yl)ethane-1-one boron difluoride complexes (2a). The specific results are shown in Table 1:

[0043] Table 1 Examples 2 to 11

[0044]

[0045] Examples 12 to 18

[0046] This example provides a series of preparation methods for N,O-boron difluoride complexes. The preparation method and raw materials are the same as those in Example 1. 1-phenyl-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2a) is prepared using different equivalents of boron source, temperature, and time. The specific results are shown in Table 2:

[0047] Table 2 Examples 12 to 18

[0048]

[0049] Example 19

[0050] This example provides a method for preparing 1-phenyl-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2b).

[0051]

[0052] 2-((4-Fluorophenyl)ethynyl)pyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 1-(4-fluorophenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2b, 27 mg, 51%).

[0053] 1 H NMR (500MHz, CDCl3) δ8.32(d,J=5.5Hz,1H),7.86–7.77(m,3H),7.23–7.16(m,2H),7.01(t,J=8.6Hz,2H),6.21(s,1H). 13 C NMR (126MHz, CDCl3) δ 163.54 (m, J = 250Hz), 151.6, 141.4, 139.8, 130.4, 128.65 (d, J = 8.8Hz), 122.4, 120.3, 115.61 (d, J = 22.0Hz), 92.9. 19 F NMR(471MHz, CDCl3)δ-109.0,-140.70,-140.73,-140.76,-140.79.IR(KBr,cm -1 ):3460,3172,3131,2360,1636,1400,1291,1088,990,853,761,535.

[0054] Example 20

[0055] This example provides a method for preparing 2-(4-nitropyridin-2-yl)-1-phenylethane-1-one boron difluoride complex (2c).

[0056]

[0057] 4-nitro-2-(phenylethynyl)pyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 2-(4-nitropyridin-2-yl)-1-phenylethane-1-one boron difluoride complex (2c, 43 mg, 74%).

[0058] 1 H NMR(500MHz,Chloroform-d)δ9.29(s,1H),8.55(dd,J=9.2,2.4Hz,1H),7.99(d,J=7.5H z,2H),7.56(t,J=7.3Hz,1H),7.49(t,J=7.6Hz,2H),7.39(d,J=9.2Hz,1H),6.56(s,1H). 13 C NMR (126MHz, CDCl3) δ168.8,155.3,140.6,138.5,134.6,133.0,132.7,128.9,127.4,122.5,93.5. 19 F NMR(471MHz,CDCl3)δ-138.95,-138.98,-139.01,-139.04.IR(KBr,cm -1 ):3547,3478,3318,3211,3092,2360,1638,1400,1088,990,553.

[0059] Example 21

[0060] This example provides a method for preparing 1-(4-bromophenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2d).

[0061]

[0062] By replacing 2-(phenylethynyl)pyridine in the example with 2-((4-bromophenyl)ethynyl)pyridine and remaining unchanged, 1-(4-bromophenyl)-2-(pyridin-2-yl)ethan-1-one boron difluoride complex (2d, 41 mg, 60%) was obtained.

[0063] 1 H NMR (500MHz, CDCl3) δ8.40(d,J=5.8Hz,1H),8.00(d,J=3.9Hz,1H),7.87(t,J=8.5Hz,1 H),7.43(d,J=6.1Hz,1H),7.33(dd,J=5.1,3.1Hz,1H),7.30–7.22(m,2H),6.19(s,1H). 13 C NMR (126MHz, CDCl3) δ158.9,151.9,141.2,139.9,137.3,132.1,128.7,127.4,126.5,125.2,122.3,120.0,93.3. 19F NMR (471MHz, CDCl3) δ-140.78,-140.81,-140.84,-140.87.

[0064] Example 22

[0065] This example provides a method for preparing 1-(4-methoxyphenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2e).

[0066]

[0067] 2-((4-methoxyphenyl)ethynyl)pyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 1-(4-methoxyphenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2e, 43 mg, 79%).

[0068] 1 H NMR (500MHz, CDCl3) δ8.39(d,J=6.1Hz,1H),7.90(d,J=8.8Hz,2H),7.86(t,J=7.8Hz,1H ),7.27(d,J=5.2Hz,3H),7.23(t,J=6.7Hz,1H),6.95(s,1H),6.28(s,1H),3.86(s,3H). 13 C NMR (126MHz, CDCl3) δ163.0,162.0,152.0,141.0,139.7,128.3,122.2,119.5,113.9,91.7,55.4. 19 F NMR(471MHz, CDCl3)δ-140.92,-141.95,-141.98,-141.02.IR(KBr,cm -1 ):IR(KBr,cm -1 ):3535,3446,3229,2360,1637,1401,1292,1088,990,542.

[0069] Example 23

[0070] This example provides a method for preparing 2-(2-oxo-2-phenylethyl)isonicotinate boron difluoride complex (2f).

[0071]

[0072] By replacing 2-(phenylethynyl) pyridine in the example with 2-(phenylethynyl) isonicotinoic acid methyl ester and maintaining the other operations unchanged, 2-(2-oxo-2-phenylethyl) isonicotinoic acid methyl ester boron difluoride complex (2f, 54 mg, 89%) was obtained.

[0073] 1 H NMR (500MHz, CDCl3) δ9.04 (s, 1H), 8.38 (d, J = 8.6Hz, 1H), 7.95 (d, J = 7.3Hz, 2H) ,7.46(dt,J=14.6,7.0Hz,3H),7.33(d,J=8.6Hz,1H),6.45(s,1H),3.98(s,3H). 13 CNMR (126MHz, CDCl3) δ165.9,163.4,154.1,142.7,140.8,133.6,131.8,128.7,126.9,122.8,122.0,93.3,52.9. 19 F NMR(471MHz, CDCl3)δ-139.65,-139.68,-139.71,-139.74.IR(KBr,cm -1 ):IR(KBr,cm -1 ):3450,3216,2359,1634,1400,1292,1087,989,853,528.

[0074] Example 24

[0075] This example provides a method for preparing 1-(4-chlorophenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2e).

[0076]

[0077] 2-((4-chloro)ethynyl)pyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 1-(4-chlorophenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2 g, 42 mg, 76%).

[0078] 1 H NMR (500MHz, CDCl3) δ8.39(d,J=5.4Hz,1H),7.86(t,J=7.8Hz,1H),7.81(d,J=8.6Hz,2H),7.36(dd,J=18.6,8.6Hz,3H),7.19(s,1H),6.28(s,1H). 13C NMR (126MHz, CDCl3) δ158.9,158.8,151.9,141.2,139.9,137.3,132.0,128.7,127.4,126.5,125.2,122.3,120.0,93.3. 19 F NMR(471MHz, CDCl3)δ-140.84,-140.87,-140.90,-140.93.IR(KBr,cm -1 ):3603,3544,3341,3119,2360,1637,1399,1089,990,541.

[0079] Example 25

[0080] This example provides a method for preparing 2-(pyridin-2-yl)-1-(thiophen-2-yl)ethane-1-one boron difluoride complex (2h).

[0081]

[0082] 2-(Phenylacetyl)pyridine was used to replace the 2-(thiophen-2-yl-ethynyl)pyridine in the example, and the other operations remained unchanged to obtain 2-(pyridin-2-yl)-1-(thiophen-2-yl)ethane-1-one boron difluoride complex (2h, 34 mg, 67%).

[0083] 1 H NMR (500MHz, CDCl3) δ8.42(d,J=4.8Hz,1H),8.01(d,J=2.6Hz,1H),7.88(t,J=7.7Hz,1 H),7.44(d,J=5.0Hz,1H),7.35(dd,J=4.9,3.1Hz,1H),7.30–7.23(m,2H),6.20(s,1H). 13 C NMR (126MHz, CDCl3) δ151.9,141.2,140.0,132.1,128.6,127.5,126.5,125.2,122.2,119.9,93.3. 19 F NMR(471MHz, CDCl3)δ-140.96,-140.99,-141.03,-141.06.IR(KBr,cm -1 ):3441,3182,2359,1637,1400,1292,1088,990,535.

[0084] Example 26

[0085] This example provides a method for preparing 1-(naphthalen-2-yl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2i).

[0086]

[0087] 2-(Phenylacetyl)pyridine was substituted with 2-(naphthalene-2-ynyl)pyridine, and the other operations remained unchanged to obtain 1-(naphthalene-2-yl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2i, 21 mg, 36%).

[0088] 1 H NMR(500MHz, CDCl3)8.56(s,1H),8.47(d,J=5.6Hz,1H),7.98–7.90(m,3H),7.89–7.83 (m,2H),7.57–7.49(m,2H),7.35(d,J=8.3Hz,1H),7.30(t,J=6.7Hz,1H),6.52(s,1H). 13 C NMR (126MHz, CDCl3) δ163.0,151.8,141.2,139.9,134.2,131.0,128.5,126.5,122.4,120.2,93.1. 19 F NMR (471MHz, CDCl3) δ-140.83,-140.86,-140.90,-140.93.

[0089] Example 27

[0090] This example provides a method for preparing 2-(2-(4-methoxyphenyl)-2-oxoethyl)isonicotinonitrile boron difluoride complex (2j).

[0091]

[0092] 2-((4-methoxyphenyl)ethynyl)isonicotinonitrile was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 2-(2-(4-methoxyphenyl)-2-oxoethyl)isonicotinonitrile boron difluoride complex (2j, 54 mg, 90%).

[0093] 1 H NMR(500MHz,DMSO-d6)δ8.61(d,J=6.3Hz,1H),8.12(s,1H),7.91(d,J=8.9Hz ,2H),7.79(d,J=7.8Hz,1H),7.10(d,J=8.9Hz,2H),6.85(s,1H),3.85(s,3H). 13CNMR(126MHz,DMSO)δ163.4,162.7,152.2,141.3,128.8,128.6,127.7,125.8,124.8,121.9,116.2,114.9,92.6,56.0. 19 F NMR (471MHz, CDCl3) δ-139.82,-139.85,-139.88,-139.90.

[0094] Example 28

[0095] This example provides a method for preparing 2-(4-methoxypyridin-2-yl)-1-phenylethane-1-one boron difluoride complex (2k).

[0096]

[0097] 4-methoxy-2-(phenylethynyl)pyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 2-(4-methoxypyridin-2-yl)-1-phenylethane-1-one boron difluoride complex (2k, 25 mg, 41%).

[0098] 1 H NMR (500MHz, CDCl3) δ8.04(s,1H),7.92(d,J=3.7Hz,2H),7.55(d,J=11.6Hz,1H),7.42(d,J=5.6Hz,3H),7.25(s,1H),6.33(s,1H),3.92(s,3H). 13 C NMR (126MHz, CDCl3) δ146.0,131.9,131.0,130.5,128.5,126.2,123.5,92.8,56.5. 19 F NMR(471MHz, CDCl3)δ-141.62,-141.65,-141.69,-141.72.IR(KBr,cm -1 ):3447,3114,2359,1638,1401,1292,1088,990,667,531.

[0099] Example 29

[0100] This example provides a method for preparing 1-(4-methoxyphenyl)-2-(4-methylpyridin-2-yl)ethane-1-one boron difluoride complex (21).

[0101]

[0102] 2-((4-methoxyphenyl)ethynyl)-4-methylpyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 1-(4-methoxyphenyl)-2-(4-methylpyridin-2-yl)ethane-1-one boron difluoride complex (2l, 48 mg, 82%).

[0103] 1 H NMR (500MHz, CDCl3) δ8.59 (s, 1H), 8.02 (d, J = 8.8Hz, 2H), 7.73 (s, 1H), 7.66 (d ,J=6.0Hz,1H),6.99(d,J=8.8Hz,2H),4.79(s,2H),3.90(s,3H),2.69(s,3H). 13 C NMR (126MHz, DMSO) δ193.2,164.4,150.3,131.2,129.6,128.8,128.1,126.3,114.7,56.2,49.1,22.1. 19 F NMR(471MHz,CDCl3)δ-150.19,-150.25.IR(KBr,cm -1 ):3484,3163,2360,1633,1400,1293,1087,989,855,764,531.

[0104] Example 30

[0105] This example provides a method for preparing 2-(2-(4-isopropylphenyl)-2-oxoethyl)isonicotinonitrile boron difluoride complex (2m).

[0106]

[0107] By replacing 2-(phenylethynyl)pyridine in the example with 2-((4-isopropylphenyl)ethynyl)isonicotinonitrile and remaining operations unchanged, 2-(2-(4-isopropylphenyl)-2-oxoethyl)isonicotinonitrile boron difluoride complex (2m, 45 mg, 72%) was obtained.

[0108] 1 H NMR(500MHz,Chloroform-d)δ8.63(d,J=4.2Hz,1H),8.46(d,J=6.1Hz,1H),7.88(d,J=8.2Hz,2H),7.68(t,J=7.2Hz ,1H),7.63–7.58(m,2H),7.54(s,2H),7.38–7.35(m,3H),7.32(d,J=7.8Hz,3H),6.41(s,1H),1.28(d,J=6.9Hz,6H).13 C NMR (126MHz, CDCl3) δ166.7,153.7,152.8,150.1,143.5,141.0,136.2,132.1,130.8,129 .0,128.4,126.9,126.0,124.8,122.8,122.3,119.6,114.9,92.2,89.3,88.6,34.2,23.7. 19 F NMR(471MHz,CDCl3)δ-139.51,-139.53,-139.57,-139.59.IR(KBr,cm -1 ):3574,3459,3254,3083,2359,1637,1400,1088,990,537.

[0109] Example 31

[0110] This example provides a method for preparing 2-(2-(4-(diphenylamino)phenyl)-2-oxoethyl)isonicotinonitrile boron difluoride complex (2n).

[0111]

[0112] By replacing 2-(phenylethynyl)pyridine in the example with 2-((4-(diphenylamino)phenyl)ethynyl)isonicotinonitrile and maintaining the remaining operations unchanged, 2-(2-(4-(diphenylamino)phenyl)-2-oxoethyl)isonicotinonitrile boron difluoride complex (2n, 27 mg, 51%) was obtained.

[0113] 1 H NMR (500MHz, DMSO-d6) δ8.41(d,J=5.7Hz,2H),8.13(t,J=7.3Hz,2H),7.82(d,J=8.9Hz ,4H),7.57(d,J=8.3Hz,2H),7.43(t,J=6.6Hz,2H),6.82(d,J=9.0Hz,4H),6.68(s,2H). 13 C NMR (126MHz, DMSO-d6) δ162.2,152.5,151.8,142.5,139.6,128.0,122.8,120.7,120.4,111.9,90.7. 19 F NMR(471MHz,DMSO-d6)δ-141.94,-141.98,-141.04.IR(KBr,cm -1 ):3530,3353,3174,3090,2360,1638,1401,1088,990,523.

[0114] Example 33

[0115] This example provides a method for preparing 1-phenyl-2-(3-hydroxypyridin-2-yl)ethane-1-one boron difluoride complex (2o

[0116]

[0117] 2-(Phenylethynyl)-3-hydroxypyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 1-phenyl-2-(3-hydroxypyridin-2-yl)ethane-1-one boron difluoride complex (2o, 25 mg, 41%).

[0118] 1 H NMR (500MHz, DMSO) δ8.68 (s, 1H), 8.58 (d, J = 7.0Hz, 1H), 8.02 (s, 2H), 7.74 (s, 2H), 7.52 (s, 3H). 13 C NMR (126MHz, DMSO) δ163.6,142.9,132.0,129.8,127.8,126.6,125.7,120.7. 19 F NMR(471MHz,DMSO)δ-148.10,-148.16,.

[0119] Example 34

[0120] This example provides a method for preparing 1-phenyl-2-(5-nitropyridin-2-yl)ethane-1-one boron difluoride complex (2p

[0121]

[0122] 5-nitro-2-(phenylethynyl)pyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 1-phenyl-2-(5-nitropyridin-2-yl)ethane-1-one boron difluoride complex (2p, 41 mg, 71%).

[0123] 1 H NMR (500MHz, CDCl3) δ9.29 (s, 1H), 8.55 (dd, J = 9.2, 2.3Hz, 1H), 7.99 (d, J = 7.6Hz, 2H ),7.56(t,J=7.3Hz,1H),7.49(t,J=7.6Hz,2H),7.39(d,J=9.2Hz,1H),6.56(s,1H). 13C NMR (126MHz, CDCl3) δ168.78,155.36,138.50,134.63,132.73,128.88,127.35,122.51,93.53. 19 F NMR(471MHz, CDCl3)δ-138.96,-138.98,139.01,139.04.

[0124] Example 35

[0125] This example provides a method for preparing 1-(2-chlorophenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2q).

[0126]

[0127] 2-((2-chloro)ethynyl)pyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 1-(2-chlorophenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2q, 22 mg, 40%).

[0128] 1 H NMR (500MHz, CDCl3) δ8.47(d,J=5.5Hz,1H),7.96(t,J=7.8Hz,1H),7.81(dd,J =5.9,3.6Hz,1H),7.44(dd,J=5.8,3.5Hz,1H),7.38-7.33(m,4H),6.42(s,1H). 13 C NMR (126MHz, CDCl3) δ159.0,151.9,141.2,140.0,137.2,127.5,126.5,125.2,122.2,119.9,93,3. 19 F NMR (471MHz, CDCl3) δ-140.91,-140.95,-140.98,-141.01.

[0129] Example 36

[0130] This example provides a method for preparing 1-(3-chlorophenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2r).

[0131]

[0132] 2-((3-chloro)ethynyl)pyridine was used to replace 2-(phenylethynyl)pyridine in the example, and the other operations remained unchanged to obtain 1-(3-chlorophenyl)-2-(pyridin-2-yl)ethane-1-one boron difluoride complex (2r, 22 mg, 40%).

[0133] 1 H NMR (500MHz, CDCl3) δ8.47(d,J=5.3Hz,1H),8.00-7.94(m,1H),7.93(s,1H),7.82(d,J=7.7Hz,1H),7.45-7.35(m,3H),7.33(s,1H),6.37(s,1H). 13 C NMR (126MHz, CDCl3) δ161.3,151.4,141.5,140.2,134.7,130.8,129.8,126.6,124.6,122.6,120.7,93.8. 19 F NMR (471MHz, CDCl3) δ-140.78,-140.81,-140.84,-140.87.

[0134] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a N,O-boron difluoride complex, characterized in that: The pyridine acetylene compound represented by formula (1) is used as a raw material, tetrafluoroboric acid or boron trifluoride ether is used as a boron source, and a reaction is carried out in a solvent to prepare the N,O-boron difluoride complex represented by formula (2). The reaction formula is as follows: Among them, R 1 is C1-C6 alkyl, C1-C6 alkoxy, halogen, cyano, nitro, hydroxyl or C1-C4 ester; R 2 It is a substituted or unsubstituted C6-C14 aryl group; or a C4-C10 heteroaryl group, wherein the substitution is by one or more of C1-C4 alkyl, C1-C4 alkoxy, halogen or N,N-diphenylamino. When the substitution is at multiple sites, the substituents in the substitution are the same or different.

2. The preparation method according to claim 1, characterized in that R 1 is a C1-C6 alkyl group, a C1-C4 alkoxy group, a halogen group, a cyano group, a nitro group, a hydroxyl group or a C1-C4 ester group.

3. The preparation method according to claim 1, characterized in that R 2 It is a substituted or unsubstituted C6-C12 aryl group or a C4-C8 heteroaryl group.

4. The preparation method according to claim 1, characterized in that The molar ratio of the pyridine acetylene compound represented by formula (1) to the boron source is 1:1-10.

5. The preparation method according to claim 4, characterized in that The molar ratio of the pyridine acetylene compound represented by formula (1) to the boron source is 1:2-5.

6. The preparation method according to claim 1, characterized in that The solvent is one or more of toluene, fluorobenzene, nitrobenzene, trifluorotoluene or water.

7. The preparation method according to claim 1, characterized in that The reaction temperature is 80-150°C.

8. The preparation method according to claim 7, characterized in that The reaction temperature is 110-120°C.

9. The preparation method according to claim 1, characterized in that The reaction time is 24 to 48 hours.

10. The preparation method according to claim 9, characterized in that The reaction time is 30 to 40 hours.

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