A type of sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex and its synthesis method and application

Abstract

The present invention belongs to the technical field of chemical synthesis and metal organic catalysis, and specifically relates to a type of sulfobetaine inner salt type heterodiaza heterocyclic carbene palladium complex and its synthesis method and application. Firstly, a quaternary ammonium cation type diaza heterocyclic carbene palladium complex is synthesized; then a sulfonic acid anion type diaza heterocyclic carbene palladium complex is synthesized; finally, the quaternary ammonium and sulfonate modified diaza heterocyclic carbene palladium complex is subjected to a carbene ligand rearrangement reaction in water to synthesize a sulfobetaine inner salt type heterodiaza heterocyclic carbene palladium complex, and the complex has high catalytic activity when applied to a Suzuki coupling reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis and metal organic catalysis, and particularly relates to a sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex and a synthesis method and application thereof. Background Art

[0002] The chemical modifiability of nitrogen heterocyclic carbene (NHC) ligands makes them one of the most widely used ligands in metal organic chemistry, and their metal complexes have been successfully applied in various fields such as metal organic catalysis, optoelectronic materials, and drugs. In the field of metal catalysis, researchers can adjust the catalytic activity of metal centers by changing the electronic steric effect of NHC ligands; they can improve the water solubility of catalysts by introducing functional groups into NHC, thereby achieving catalytic reactions in green solvents, or achieving the loading of metal catalysts, and conveniently recovering catalysts after catalytic reactions to solve a series of problems such as the increasing cost of catalysts and the impact of heavy metal residues on product performance.

[0003] Introducing anionic and cationic substituents into NHC ligands is an effective way to improve the water solubility of nitrogen heterocyclic carbene metal catalysts [Organometallics, 2014, 33, 5470-5482; Organic & Biomolecular Chemistry, 2015, 13, 8556-8560; Applied Organometallic Chemistry, 2018, 32, 4185-4191] and is also one of the methods for loading nitrogen heterocyclic carbene metal catalysts on solid substrates through ion exchange [Applied Organometallic Chemistry, 2015, 29, 678-682], so it has attracted widespread attention. However, metal complexes with both anionic and cationic nitrogen heterocyclic carbene ligands have not been reported. Summary of the invention

[0004] In order to study the physical and chemical properties of the complex with both anionic and cationic nitrogen heterocyclic carbene ligands, i.e., the inner salt type diaza heterocyclic carbene metal complex, the present invention establishes a method for preparing the inner salt type diaza heterocyclic carbene palladium metal complex by ligand rearrangement reaction between quaternary ammonium cationic diaza heterocyclic carbene palladium complex and sulfonic acid anionic diaza heterocyclic carbene palladium complex, and obtains the sulfobetaine inner salt type heteroaza heterocyclic carbene palladium complex for the first time. The catalytic activity of the complex in the Suzuki coupling reaction is better than that of its cationic and anionic diaza heterocyclic carbene complex precursors.

[0005] The synthesis method of the quaternary ammonium cationic dinitrogen heterocyclic carbene palladium complex of the present invention is as follows: first, a bromopropyl-modified nitrogen heterocyclic precursor salt is reacted with 0.5 equivalent of silver oxide in dichloromethane for 3 hours, and then [PdBr2(CH3CN)2] is added and reacted for 20 hours to obtain a bromopropyl-modified dinitrogen heterocyclic carbene palladium complex 1. Then, the complex 1 is used as a raw material, and a tertiary amine is heated (80° C.) and refluxed in an acetonitrile solvent for 20 hours to synthesize a quaternary ammonium-modified cationic dinitrogen heterocyclic carbene palladium complex 2. The synthesis route is as follows:

[0006]

[0007] In the formula, the NHC skeleton is imidazole or benzimidazole, R is any one of benzyl, methyl, ethyl, and isopropyl, and R' is ethyl, propyl, or butyl;

[0008] The tertiary amine is NR'3, R'=Et, Pr, Bu.

[0009] The synthesis method of the sulfonic acid anion type dinitrogen heterocyclic carbene palladium complex of the present invention is: reacting a sulfonic acid propyl modified nitrogen heterocyclic precursor salt with 0.5 equivalent of silver oxide and 1 equivalent of potassium bromide in dichloromethane / methanol / water for 3 hours, adding [PdBr2(CH3CN)2] and reacting for 20 hours to obtain anionic dinitrogen heterocyclic carbene palladium complex 3. The synthesis route is as follows:

[0010]

[0011] In the formula, the NHC skeleton is imidazole or benzimidazole, and R is any one of benzyl, methyl, ethyl, and isopropyl. [PdBr2(CH3CN)2] is prepared by the in-situ reaction of palladium bromide and acetonitrile.

[0012] The synthesis method of the sulfobetaine inner salt type heterodiaza heterocyclic carbene palladium complex of the present invention is as follows: quaternary ammonium cation type heterodiaza heterocyclic carbene palladium complex 2 and sulfonic acid anion type heterodiaza heterocyclic carbene palladium complex 3 are added to a reaction bottle at an equivalent ratio of 1:1, water or a mixed solution of water and dimethyl sulfoxide is used as a solvent, and the reaction is carried out at 25 to 50° C. for 2 to 48 hours to obtain a betaine inner salt type heterodiaza heterocyclic carbene palladium complex 4. The synthesis route is as follows:

[0013]

[0014] After successfully obtaining and fully characterizing the above complexes, these complexes were used to catalyze the Suzuki coupling reaction of aryl halides with arylboronic acids.

[0015]

[0016] Experiments have shown that, compared with the cationic and anionic dinitrogen heterocyclic carbene complex precursors 2 and 3, the sulfobetaine inner salt type heterodinitrogen heterocyclic carbene palladium complex 4 of the present invention exhibits higher catalytic activity in the Suzuki coupling reaction of different substrates.

[0017] Advantages and technical effects of the present invention:

[0018] Through the rearrangement reaction of the anionic and cationic nitrogen heterocyclic carbene ligands in the quaternary ammonium cationic diazaheterocyclic carbene palladium complex 2 and the sulfonic acid anionic diazaheterocyclic carbene palladium complex 3, the present invention successfully synthesized a type of sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex 4 for the first time. Different from the anionic and cationic complexes, the inner salt type complex 4 has poor water solubility and better lipid solubility. The catalytic activity in the Suzuki coupling reaction is better than that of its cationic and anionic diazaheterocyclic carbene complex precursors 2 and 3. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Figure 2 is the single crystal structure of complexes 2a and 3a (solvent molecules are omitted).

[0020] Figure 2 This is the single crystal structure diagram of complex 4d (solvent molecules are omitted). DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the examples, wherein the structural formula of the bromopropyl-modified dinitrogen heterocyclic carbene palladium complex is

[0022] The structural formula of the nitrogen heterocyclic precursor salt modified by propyl sulfonate is The tertiary amine is NR'3, R'=Et, Pr, Bu; R is benzyl and R' is ethyl as an example, but this does not limit the present invention. When R is methyl, ethyl, isopropyl, and R' is propyl or butyl, the corresponding betaine type heterodiazaheterocyclic carbene palladium complex can also be obtained, which will not be given one by one in the examples.

[0023] Example 1

[0024]

[0025] (1) Synthesis of quaternary ammonium cationic bisimidazolyl nitrogen heterocyclic carbene palladium complex 2a

[0026] Add bromopropyl-substituted bisimidazolyl nitrogen heterocyclic carbene complex 1a (83 mg, 0.10 mmol), acetonitrile (5 mL) and triethylamine (139 μL, 1.00 mmol) into a sealed tube, heat at 80°C for 5 hours, add triethylamine (139 μL, 1.00 mmol) for the second time, and heat at 80°C for 15 hours. After the reaction, filter and collect the precipitate, and wash with acetone (5 mL × 3) to obtain a light yellow solid product 2a, 57 mg, 0.06 mmol, yield 55%, syn:anti 1:4. 1 H NMR (300MHz, DMSO-d6): δ7.51-7.47(m,11H,Ar-H),7.40-7.34(m,10H,Ar-H),7.25-7.2 2(m,7H,Ar-H); syn,5.60(s,4H,NCH2Ph),4.55(s,4H,NCH2),3.28-3.26(m,16H,CH2CH2N + and N + CH2CH3),2.45(s,4H,CH2),1.14(t,18H, 3 J H-H =7Hz,CH3);anti,5.76(s,4H,NCH2Ph),4.48(br-s,4H,NCH2),3.06-3.04(m,16H,CH2CH2N + and N + CH2CH3),2.20(br-s,4H,CH2),1.00(t,18H, 3 J H-H =7Hz,CH3). 13 C{ 1 H}NMR (100MHz, DMSO-d6): δ167.2,166.7(C carbene ),136.5,136.2,128.9,128.6,128.4,128.3,128.2,128.0,127.5,123.1,122.6,122.5(Ar-C),53.9,53.8(NCH2CH3),53.7,52.9,52.6(N + CH2,1×coincident),47.2,47.0(NCH2),23.0,22.8(CH2),7.1,6.7(CH3).Anal.Calcd.forC 38 H 60Br4N6Pd:C,44.44;H,5.89;N,8.18.Found:C,44.57;H,6.13;N,8.24.MS-ESI(m / z):[M–2Br] 2+ Calculate for C 38 H 60 Br2N6Pd 2+ 433, found 433.

[0027] (2) Synthesis of sulfonic acid anion type bisimidazolyl nitrogen heterocyclic carbene palladium complex 3a

[0028] PdBr2 (27 mg, 0.10 mmol) was heated to reflux in CH3CN (15 mL) for 1 hour to obtain [PdBr2 (CH3CN) 2] solution. At the same time, sulfonate propyl substituted imidazole precursor salt (46 mg, 0.20 mmol) and KBr (24 mg, 0.20 mmol) were dissolved in a mixed solvent of MeOH and 3 drops of H2O, Ag2O (23 mg, 0.10 mmol) was added in dark and stirred at room temperature for 3 hours, then [PdBr2 (CH3CN) 2] solution was slowly added dropwise to Ag-NHC, stirred at room temperature for 20 hours, the solid and liquid phases were separated and the solid phase was collected, H2O (5 mL × 5) was added to dissolve the product, and the aqueous phase was collected and dried to obtain an off-white solid product 3a, 73 mg, 0.08 mmol, 81%, syn:anti 1.1:1. 1 H NMR(300MHz,DMSO-d6):δ7.62(d,4H, 3 J H-H =7Hz,Ar-H),7.50-7.47(m,4H,Ar-H),7.37-7.30(m,10H,Ar-H),7.24(t,6H, 3 J H-H =3Hz,Ar-H),7.12(dd,4H, 3 J H-H =4Hz,2Hz,Ar-H); syn,5.57(s,4H,NCH2Ph),4.55(t,4H, 3 J H-H =7Hz,NCH2),2.56-2.54(m,4H,CH2S)2.39-2.33(m,4H,CH2);anti,5.67(s,4H,NCH2Ph),4.46(t,4H, 3 J H-H =7Hz,NCH2),2.39-2.33(m,4H,CH2S),2.30-2.23(m,4H,CH2). 13 C{ 1H}NMR (100MHz, DMSO-d6): δ168.4,168.3(C carbene ),136.9,136.9,128.5,128.4,128.4,128.3,127.8,127.6,122.6,122.5,120.9,120.8(Ar-C) ,53.3,53.2(NCH2Ph),48.9,48.8(NCH2),48.2,48.0(SCH2),26.7,26.6(CH2).Anal.Calcd.for C 26 H 30 Br2K2N4O6PdS2:C,34.58;H,3.35;N,6.20.Found:C,34.66;H,3.28;N,6.43.MS-ESI(m / z):[M+CH3CN+H] + Calculate for C 28 H 34 Br2K2N5O6PdS2 + 944, found 944.

[0029] (3) Synthesis of sulfobetaine inner salt type heterobiimidazole nitrogen heterocyclic carbene palladium complex 4a

[0030] Complex 2a (103 mg, 0.10 mmol) and complex 3a (91 mg, 0.10 mmol) were dissolved in H2O (10 mL) and stirred at room temperature for 2 hours to obtain a suspension. After filtration, the residue was washed with H2O (3×5 mL) to obtain the product as a yellow solid (144 mg, 0.17 mmol, 85%). 1 H NMR(300MHz, CDCl3): δ7.67(d,1H, 3 J H-H =2Hz,Ar-H),7.40-7.37(m,5H,Ar-H),7.30-7.26(m,2H,Ar-H),7.26-7.25(m,3H,Ar-H),6.89(d,1H, 3 J H-H =2Hz,Ar-H),6.65(s,2H,Ar-H),5.63(s,2H,NCH2Ph),5.59(s,2H,NCH2Ph),4.86(t,2H, 3 J H-H =6Hz,NCH2),4.77(t,2H, 3 J H-H =8Hz,NCH2),3.92-3.90(m,2H,CH2CH2N +),3.33(q,6H, 3 J H-H =7Hz,N + CH2CH3),3.06(t,2H, 3 J H-H =6Hz,CH2S),2.56-2.46(m,4H,CH2),1.29(t,9H, 3 J H-H =7Hz,CH3). 13 C{ 1 H}NMR (75MHz, DMSO-d6): δ169.0,167.4(C carbene ),136.8,136.6,128.4,128.3,128.2,127.9,127.7,127.6,122.2,122.0,121.7,121.1(Ar-C),53.4,53.1(NCH2Ph),52.0(N + CH2,1×coincident),49.7(NCH2,1×coincident),49.2(CH2S),27.0,22.8(CH2),7.1(CH3).Anal.Calcd.for C 32 H 45 Br2N5O3PdS:C,45.32;H,5.59;N,8.26.Found:C,45.21;H,5.87;N,8.39.MS-ESI(m / z):[M–Br] + Calculate for C 32 H 45 BrN5O3PdS + 764,found764.

[0031] Example 2

[0032]

[0033] (1) Synthesis of quaternary ammonium cationic bisbenzimidazole nitrogen heterocyclic carbene palladium complex 2b

[0034] Bromopropyl-substituted bisbenzimidazole nitrogen heterocyclic carbene complex 1b (93 mg, 0.10 mmol), acetonitrile (5 mL) and triethylamine (139 μL×2, 2.00 mmol) were added to a sealed tube and heated at 80°C for 20 hours. After the reaction, the solvent was drained and the residue was washed with acetone (5 mL×3) to give a light yellow solid product 2b, 67 mg, 0.06 mmol, with a yield of 59%.

[0035] (2) Synthesis of Sulfonic Acid Anion-Type Bisbenzimidazole Nitrogen Heterocyclic Carbene Palladium Complex 3b

[0036] PdBr2 (53 mg, 0.20 mmol) was heated to reflux in CH3CN (15 mL) for 1 hour to obtain [PdBr2 (CH3CN) 2] solution. At the same time, sulfonic acid propyl substituted benzimidazole precursor salt (132 mg, 0.40 mmol) and KBr (48 mg, 0.40 mmol) were dissolved in a mixed solvent of DCM (6 mL) and MeOH (2 mL), and Ag2O (47 mg, 0.20 mmol) was added in dark and stirred at room temperature for 3 hours. [PdBr2 (CH3CN) 2] solution was slowly added dropwise to Ag-NHC, stirred at room temperature for 20 hours, separated the solid and liquid phases and collected the solid phase, added H2O (5 mL × 5) to dissolve the product, and the aqueous phase was collected and dried to obtain a dark green solid product 3b, 137 mg, 0.14 mmol, 68%, syn:anti 1.3:1. 1 H NMR (300MHz, DMSO-d6): δ7.85-7.79(m,7H,Ar-H),7.61(s,5H,Ar-H),7.38-7.33(m,13H,Ar-H),7.23(s,11H,Ar-H); syn,5.99(s,4H,NCH2Ph),5.05(br- s,4H,NCH2),2.81(br-s,4H,SCH2),2.40(br-s,4H,CH2); anti,6.13(s,4H,NCH2Ph),4.95(br-s,4H,NCH2),2.53(br-s,4H,SCH2),2.40(br-s,4H,CH2). 13 C{ 1 H}NMR (75MHz, DMSO-d6): δ181.1,181.0(C carbene ),135.9,135.8,134.3,133.6,133.5,128.6,128.4,128.2,128.1,128.0,127.9,127.8,123.3,123.1,111.5,111.3( Ar-C,4×coincident),51.6,51.5(NCH2Ph),48.4,47.9(NCH2),46.9,46.7(SCH2),25.8,25.7(CH2).Anal.Calcd.forC 34 H 34 Br2K2N4O6PdS2:C,40.71;H,3.42;N,5.58.Found:C,40.55;H,3.32;N,5.76.MS-ESI(m / z):[M–2Br]2+ Calculate for C 32 H 34 K2N4O6PdS2 2+ 842, found 842.

[0037] (3) Synthesis of sulfobetaine inner salt type heterobibenzimidazole nitrogen heterocyclic carbene palladium complex 4b

[0038] Complex 2b (90 mg, 0.08 mmol) was dissolved in DMSO (5 mL), and complex 3b (80 mg, 0.08 mmol) was dissolved in H2O (5 mL). The two were mixed in a 50 mL round-bottom flask and stirred at 50°C for 2 days. The solvent was evaporated under reduced pressure and the crude product was purified by silica gel column chromatography (eluent: dichloromethane / methanol = 1 / 20, V / V) to obtain a light yellow solid product 4b (18 mg, 0.02 mmol, 12%). 1 H NMR(400MHz, CDCl3): δ7.59(d,1H, 3 J H-H =7Hz,Ar-H),7.44(d,1H, 3 J H-H =7Hz,Ar-H),7.35-7.32(m,5H,Ar-H),7.22(d,1H, 3 J H-H =7Hz,Ar-H),7.18-7.17(m,7H,Ar-H),7.08-7.04(m,4H,Ar-H),5.91(s,2H,NC H2Ph),5.88(s,2H,NCH2Ph),5.12-5.08(m,4H,NCH2),3.84(br-s,2H,CH2CH2N + ),3.24-3.22(m,6H,N + CH2CH3),2.96(br-s,2H,CH2S),2.63-2.59(m,4H,CH2),1.15(br-s,9H,CH3). 13 C{ 1 H}NMR (100MHz, CDCl3): δ182.8,180.2(C carbene),135.3,135.1,134.6,134.4,134.1,128.7,128.6,127.9,127.8,127.7,127.7,123.6,123.4,123 .2,123.1,111.6,111.3,110.7,110.6(Ar-C,1×coincident),54.9(NCH2Ph,1×coincident),53.2(N + CH2,1×coincident),52.7,52.5(NCH2),47.9(CH2S),25.5,22.1(CH2),7.6(CH3).Anal.Calcd.for C 40 H 49 Br2N5O3PdS:C,50.78;H,5.22;N,7.40.Found:C,50.89;H,5.33;N,7.39.MS-ESI(m / z):[M–Br] + Calculate for C 40 H 49 BrN5O3PdS + 864, found 864.

[0039] Example 3

[0040]

[0041] Synthesis of sulfobetaine inner salt type heterobiimidazole-benzimidazole nitrogen heterocyclic carbene palladium complex 4c: Complex 2b (90 mg, 0.08 mmol) was dissolved in DMSO (5 mL), and complex 3a (72 mg, 0.08 mmol) was dissolved in H2O (5 mL). The two were mixed in a 50 mL round-bottom flask and stirred at room temperature for 2 days. The solvent was evaporated under reduced pressure and the crude product was purified by silica gel column chromatography (eluent: dichloromethane / methanol = 1 / 20, V / V) to obtain the product as a light yellow solid 4c (53 mg, 0.06 mmol, 37%). 1 H NMR(300MHz, CDCl3): δ7.90(d,1H, 3 J H-H =8Hz,Ar-H),7.48-7.45(m,2H,Ar-H),7.34-7.31(m,2H,Ar-H),7.24-7.22(m,7H,Ar-H),7.05-7.02(m,2H,Ar-H),6.96(d,1H, 3 J H-H =2Hz,Ar-H),6.67(d,1H, 3 J H-H= 2 Hz, Ar-H), 5.96 (s, 2H, NCH2Ph), 5.58 (s, 2H, NCH2Ph), 5.17 (br-s, 2H, NCH2), 4.81 (t, 2H, 3 J H-H = 7 Hz, NCH2), 3.99 - 3.98 (m, 2H, CH2CH2N + ), 3.35 (d, 6H, 3 J H-H = 7 Hz, N + CH2CH3), 3.13 (t, 2H, 3 J H-H = 7 Hz, CH2S), 2.70 (br-s, 2H, CH2), 2.59 (br-s, 2H, CH2), 1.21 (t, 9H, 3 J H-H = 7 Hz, CH3). 13 C{ 1 H} NMR (75 MHz, CDCl3): δ 182.8, 167.5 (C carbene ), 135.8, 135.3, 134.2, 128.6, 128.5, 127.9, 127.8, 123.6, 123.0, 121.4, 120.9, 111.5, 111.1 (Ar-C, 3×coincident), 54.3, 53.2 (NCH2Ph), 52.7 (CH2CH2N + , 1×coincident), 50.7, 49.4 (NCH2), 45.3 (CH2S), 27.2, 22.4 (CH2), 7.8 (CH3). Anal. Calcd. for C 36 H 47 Br2N5O3PdS: C, 48.25; H, 5.29; N, 7.82. Found: C, 48.43; H, 4.99; N, 7.54. MS-ESI (m / z): [M–Br] + calcd for C 36 H 47 BrN5O3PdS + 814, found 814.

[0042] Example 4

[0043]

[0044] Synthesis of sulfobetaine inner salt type heterobibenzimidazole-imidazole nitrogen heterocyclic carbene palladium complex 4d: Complex 2a (80 mg, 0.08 mmol) was dissolved in H2O (5 mL), and complex 3b (82 mg, 0.08 mmol) was dissolved in DMSO (5 mL). The two were mixed in a 50 mL round-bottom flask and stirred at room temperature for 2 days. The solvent was evaporated under reduced pressure and the crude product was purified by silica gel column chromatography (eluent: dichloromethane / methanol = 1 / 20, V / V) to obtain a light yellow solid product 4d (60 mg, 0.07 mmol, 42%). 1 HNMR (300MHz, CDCl3): δ7.69(s,1H,Ar-H),7.47-7.39(m,4H,Ar-H),7.33-7.31(m,2H,Ar-H),7.23-7.21(m,6H,Ar-H),7.06-7.04(m,2H,A r-H),6.66(s,1H,Ar-H),5.97(s,2H,NCH2Ph),5.55(s,2H,NCH2Ph),5.11(br-s,2H,NCH2),4.88(br-s,2H,NCH2),3.85(br-s,2H,CH2CH2N + ),3.32(q,6H, 3 J H-H =6Hz,N + CH2CH3),3.18(br-s,2H,CH2S),2.61(br-s,4H,CH2),1.25(br-s,9H,CH3). 13 C{ 1 H}NMR (75MHz, CDCl3): δ181.8,168.7(C carbene ),135.9,135.6,134.7,134.6,128.7,128.1,128.0,127.9,122.9,121.4,111.4,110.6(Ar-C,4×coincident),54.8,54.4(NCH2Ph),53.2(N + CH2CH3),52.8(CH2CH2N + ),49.9,48.2(NCH2),47.5(CH2S),25.7,22.8(CH2),7.9(CH3).Anal.Calcd.for C 36 H 47 Br2N5O3PdS:C,48.25;H,5.29;N,7.82.Found:C,48.39;H,5.53;N,7.69.MS-ESI(m / z):[M–Br] +Calculate for C 36 H 47 BrN5O3PdS + 814, found 814.

[0045] Example 5 Catalytic Application of the Complex of the Present Invention

[0046] In an air atmosphere, aryl halide (0.20mmol), palladium catalyst (2a-4a, 0.002mmol), phenylboronic acid (0.24mmol, 29mg), K2CO3 (0.30mmol, 42mg), H2O (600μL), and internal standard dodecane (0.20mmol) were added to the reaction flask. After the reaction was completed, dichloromethane (2mL) and H2O (2mL) were added for extraction. After the organic phase was dried over anhydrous sodium sulfate, 3 drops of crude product were taken and diluted to 2mL with dichloromethane, and quantitative analysis was performed by gas chromatography.

[0047] The results show that the inner salt complex 4a exhibits higher catalytic activity than the cationic and anionic dinitrogen heterocyclic carbene complex precursors 2a and 3a for the Suzuki coupling reaction of seven aromatic substrates with different substituents and different halogen substitutions (Table 1). In particular, the coupling reaction of p-chloroacetophenone, with the addition of TBAB, the yield of complex 4a catalyzed by the reaction was 86%, which reflects the catalytic advantage of the inner salt complex to a certain extent.

[0048] Table 1 a

[0049]

[0050] a Reaction conditions: aryl halide (0.20 mmol), phenylboronic acid (0.24 mmol), potassium carbonate (0.30 mmol), catalyst (0.1 mol% [Pd]), H2O (600 uL), air atmosphere. b The GC yield, with n-dodecane as the internal standard, is the average of two parallel reactions. c TBAB (0.30 mmol).

[0051] Table 2

[0052]

Claims

1. A sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex, characterized in that: The complex contains a quaternary ammonium-modified cationic nitrogen heterocyclic carbene ligand and a sulfonate-modified anionic nitrogen heterocyclic carbene ligand; the specific structure of the sulfobetaine inner salt type heterodiaza heterocyclic carbene palladium complex is as follows: The skeleton of the nitrogen heterocyclic carbene is imidazole or benzimidazole, R is any one of benzyl, methyl, ethyl and isopropyl, and R' is ethyl, propyl or butyl.

2. A method for synthesizing the sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex according to claim 1, characterized in that: The synthesis method steps are as follows: (1) Synthesis of quaternary ammonium cationic dinitrogen heterocyclic carbene palladium complexes; (2) Synthesis of sulfonic acid anion type dinitrogen heterocyclic carbene palladium complex; (3) Synthesis of sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex.

3. The method for synthesizing the sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex according to claim 2, characterized in that: The synthesis method of the quaternary ammonium cationic dinitrogen heterocyclic carbene palladium complex described in step (1) is: using a bromopropyl-modified dinitrogen heterocyclic carbene palladium complex and a tertiary amine as raw materials, using acetonitrile as solvent, heating and reflux reaction at 80° C. in a sealed tube for 20 hours to synthesize the quaternary ammonium cationic dinitrogen heterocyclic carbene palladium complex, and the equivalent ratio of the two is 1:

20.

4. The method for synthesizing the sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex according to claim 3, characterized in that: The structural formula of the bromopropyl-modified dinitrogen heterocyclic carbene palladium complex is The tertiary amine is NR'3, R'=Et, Pr, Bu.

5. The method for synthesizing the sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex according to claim 2, characterized in that: The synthesis method of the sulfonate anionic dinitrogen heterocyclic carbene palladium complex described in step (2) is as follows: a sulfonate propyl-modified nitrogen heterocyclic precursor salt is reacted with 0.5 equivalent of silver oxide and 1 equivalent of potassium halide in dichloromethane / methanol / water for 3 hours, and then 0.5 equivalent of [PdBr2(CH3CN)2] is added and reacted for 20 hours to obtain an anionic dinitrogen heterocyclic carbene palladium complex.

6. The method for synthesizing the sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex according to claim 5, characterized in that: The structural formula of the nitrogen heterocyclic precursor salt modified by propyl sulfonate is:

7. The method for synthesizing the sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex according to claim 2, characterized in that: In step (3), water or a mixture of water and dimethyl sulfoxide is used as a solvent, and a cationic dinitrogen heterocyclic carbene palladium complex and an anionic dinitrogen heterocyclic carbene palladium complex undergo a ligand rearrangement reaction to obtain a sulfobetaine inner salt type heterodinitrogen heterocyclic carbene palladium complex.

8. The method for synthesizing the sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex according to claim 7, characterized in that: The equivalent ratio of the cationic dinitrogen heterocyclic carbene palladium complex to the anionic dinitrogen heterocyclic carbene palladium complex is 1:1, and the reaction is carried out at 25-50°C for 2-48h.

9. The use of the sulfobetaine inner salt type heterodiazaheterocyclic carbene palladium complex according to claim 1, characterized in that: The complex is used to catalyze the Suzuki coupling reaction.

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