English

• 1.   Introduction

  The palladium catalyzed direct arylation of heteroarenes with aryl halides is widely used in polymer chemistry, functional material synthesis, biological sciences, and natural product chemistry.^[1~4] In recent years, direct arylation reactions have emerged as attractive alternatives to the traditional coupling reactions, which add costly chemical steps to the overall synthesis by pre-activation arenes.^[5] Among the available methods, various types of palladium catalytic systems have been studied, including a ligand free pallidum catalyst system^[6] or Pd(OAc)₂ associated with some sterically demanding, electron-rich phosphines system.^[7~11] Despite the significant progress has been achieved, some catalytic systems still suffer from disadvantages: poor substrate scope or high palladium loading. Recently, N-heterocyclic carbene ligand^[12] and diimine ligand^[13] palladium complexes catalyzed C—H arylation reactions have been reported, in which two catalytic systems made a significant progress in this area with K₂CO₃ as base and pivalate acid (PivOH) as additive.

  Research in the structure-activity relationship of previously reported palladium catalysts found that the strong donor strength and high steric hindrance demand of ligands are directly related to the catalytic activities of complexes.^{[12, 13]} Carbazole is a strong electron-donating group and commonly used as ligand for metal complexes synthesis. A series of metal complexes based on carbazole skeleton are synthesized, such as ruthenium, ^[14] copper, ^[15] iridium, ^[16] platinum, ^[17] nickel, ^[18] and found widely applications in the advanced material synthesis.^[19~21] However, the catalytic performance of carbazole-based metal complexes in the organic transformations was rarely investigated. In 2003, Nakada and co-workers^[22] reported a new carbazole-based chiral ligand which can be used for the asymmetric Nozaki-Hiyama allylation and methallylation reaction. It indicates that carbazole has potential applications as a ligand in the field of catalysis. Then, Kunz and co-workers^[23] synthesized a class of efficient carbazole-based rhdium complexes for selective rearrangement of terminal epoxides into methylketones. Based on previous studies, Gade and co-workers^[24] described the synthesis of carbazole-based PNP type iron complexes, which was shown to be efficient in the hydrogenation of alkenes. Over the past few years, our group has successfully proved the unsymmetrical pyridine-bridged pincer-type scaffolds as effective ligands or catalysts for iron-catalyzed, and organocatalyzed the cycloaddition of epoxides with CO₂, ^[25] as well as palladium complexes catalyzed the Suzuki cross-coupling reaction based on our group ligand.^[26] Within our program on design and synthesis of unsymmetrical pyridine-bridged catalysts, ^[27] we have now developed a series of carbazole-pyridine-based palladium complexes, and found that these palladium complexes were efficient for direct arylation reaction of imidazole, thiazole and other N-hetero- cyclic compounds. The functional-group tolerance and substrate scope have also been studied. In addition, studies in this literature in direct arylation reaction using a single component KOAc as base.

  2.   Results and discussion

  The preparation of carbazole-based palladium(II) complexes C1~C6 is shown in Scheme 1. Ligands L1~L6 were synthesized via continuous coupling of 2-hydroxy- carbazole with 2-fluoropyridines in N, N-dimethylform- amide (DMF) at 150 ℃ for 12 h with excellent yields, ^[27] followed by the reaction between ligands L1~L6 and PdCl₂ in acetonitrile at 80 ℃. The palladium complexes C1~C6 were stable to air and moisture, even for 15 d under an air atmosphere. In order to understand the coordination form of the complexes, the molecular structure of C1 was confirmed by X-ray crystallography (Figure 1). The single crystal structure of C1 proves that the carbazole coordinated with palladium via the C—H bond activation on the carbazole ring.

  Scheme 1

  

  Scheme 1.  Synthesis of carbazole-based palladium complexes C1~C6

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  图 1

  

  Figure 1.  X-ray structure of palladium complex C1

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  In order to investigate the catalytic activity of palladium complexes C1~C6, the reaction of 1-methy-1H-imidazole 1a with 4-bromoacetophenone 2b was selected as a model reaction (Table 1). When the reaction was conducted in N, N-dimethylacetamide (DMA) using palladium complex C1 as catalyst and KOAc as base at 140 ℃, the desired arylated product 3b was isolated in 75% yield (Table 1, Entry 1). It is noteworthy that 1-methy-1H-imidazole underwent highly selective coupling at C-5 position rather than that of C-2 and C-4, which is consistent with the previously reported results.^{[12, 13, 28]} Moreover, the palladium complexes C2~C5 which bearing electron-withdrawing group, such as iodide, bromide, chloride, and benzene were also investigated under the same reaction conditions, affording the desired product in the yields of 86%, 82%, 87%, and 84%, respectively (Table 1, Entries 2~5). To further explore the influence of substituents on the palladium complexes, the palladium complex C6 with electron-donating methyl group was also tested. The result showed that lower conversion of starting material 1a was observed compared with that of C2~C5 under the same reaction conditions, leading to the desired product in 65% yield (Table 1, Entry 6). The above results suggested that the electronic nature of substituents with palladium complexes has the effect on the catalytic efficiency. In addition, the influence of ligands in catalytic efficiency was also explored. Pd(OAc)₂ and PdCl₂ in the absence of ligands have been tested and moderate yields of 60% and 46% were obtained (Table 1, Entries 7, 8). However, the PdCl₂ or Pd(OAc)₂ in the presence of the commercial ligands such as PCy₃, PPh₃, 1, 10-phenanthroline and bipyridine has not improve the catalytic efficiency (Table 1, Entries 9~12), only PdCl₂ in combination with bipyridine showed the relatively higher catalytic activity (Table 1, Entry 12). When our developed C4 palladium complex has been used as catalyst and a significant improvement was observed (Table 1, Entry 4). The compared experiments suggested that the rational design of catalysts plays an important role in tuning the catalytic activity.

  表 1

  

  Table 1.  Optimization of conditions for direct arylation reaction^a

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  Entry	Cat. (mol%)	Solvent	Base	Temp./℃	Time/h	Yield/%
  1	C1 (2)	DMA	KOAc	140	10	75
  2	C2 (2)	DMA	KOAc	140	10	86
  3	C3 (2)	DMA	KOAc	140	10	82
  4	C4 (2)	DMA	KOAc	140	10	87
  5	C5 (2)	DMA	KOAc	140	10	84
  6	C6 (2)	DMA	KOAc	140	10	65
  7	Pd(OAc)2 (2)	DMA	KOAc	140	10	60
  8	PdCl2 (2)	DMA	KOAc	140	10	46
  9	Pd(OAc)2/PCy3 (2)	DMA	KOAc	140	10	53
  10	Pd(OAc)2/PPh3 (2)	DMA	KOAc	140	10	52
  11	PdCl2/Phth (2)	DMA	KOAc	140	10	31
  12	PdCl2/Bipy (2)	DMA	KOAc	140	10	64
  14	C4 (2)	DMA	K2CO3	140	10	35
  15	C4 (2)	DMA	K3PO4	140	10	52
  16	C4 (2)	DMA	KF	140	10	46
  17	C4 (2)	DMA	KOtBu	140	10	Trace
  18	C4 (2)	DMA	LiOtBu	140	10	Trace
  19	C4 (2)	DMA	CsF	140	10	40
  20	C4 (2)	DMA	Cs2CO3	140	10	20
  21	C4 (2)	DMF	KOAc	140	10	30
  22	C4 (2)	DMSO	KOAc	140	10	60
  23	C4 (2)	NMP	KOAc	140	10	83
  24	C4 (2)	Toluene	KOAc	140	10	Trace
  25	C4 (2)	Dioxane	KOAc	140	10	Trace
  26	C4 (2)	EG	KOAc	140	10	10
  27	C4 (2)	DMA	KOAc	140	12	94
  28	C4 (1.5)	DMA	KOAc	140	12	93
  29	C4 (1)	DMA	KOAc	140	12	76
  30	C4 (1.5)	DMA	KOAc	130	12	75
  31	C4 (1.5)	DMA	KOAc	120	12	43
  32b	C4 (1.5)	DMA	K2CO3	130	12	74
  a Reaction conditions: 4-bromoacetophenone (1.0 mmol), 1-methyl-1H-imidazole (2.0 mmol), catalyst (amount as indicated in this table), base (2.0 mmol), solvent (3.0 mL), under aerobic condition, isolated yield. b PivOH (0.3 mmol). Abbreviations: DMA, N, N-dimethylacetamide; DMF, N, N-dimethylformamide; DMSO, dimethyl sulfoxide; NMP, N-methyl-2-pyrrolidone; EG, Ethylene glycol; Phth, 1, 10-phenanthroline; Bipy, bipyridine.

  Next, the palladium complex C4 was employed as catalyst. A variety of bases were investigated (Table 1, Entries 14~20). K₂CO₃, K₃PO₄, KF and CsF gave moderate yields (Table 1, Entries 14~16, 19). However, KO^tBu, LiO^tBu, and Cs₂CO₃ in this reaction exhibited the poor results (Table 1, Entries 17~18, 20). KOAc was the most effective and gave desired arylation product 3b at C-5 position in 87% isolated yield (Table 1, Entry 4). The influence of solvent on direct C—H bond arylation of imidazole was further examined. Screening of solvents revealed that DMA was the best solvent (Table 1, Entry 4), whereas DMF, dimethyl sulfoxide (DMSO), toluene, dioxane and ethylene glycol (EG), gave poor to moderate product yield (Table 1, Entries 21, 22, 24~26). The good yield was obtained when the reaction was performed in NMP giving the desired product in 83% yield (Table 1, Entry 23). We also tried to extend the reaction time to 12 h and 94% yield of 3b was obtained (Table 1, Entry 27). There was no effect on the reaction when the loading of the catalyst C4 reduced from 2 mol% to 1.5 mol% (Table 1, Entries 27, 28), while catalytic efficiency was dramatically decreased when the catalyst loading lowed to 1 mol% (Table 1, Entry 29). The effect of temperature was also investigated in this reaction, the yield of 3b could reach to 75% when the temperature was lowered to 130 ℃, while catalytic efficiency was dramatically decreased when the temperature lowed to 120 ℃ (Table 1, Entries 30, 31). PivOH was usually used in the catalytic system as additive with K₂CO₃ as base in previous reports.^{[12a~12e, 13, 29]} The binary system of K₂CO₃ and PivOH did not show an obvious improvement in the isolated yield compared with the reaction used KOAc as sole base under 130 ℃ (Table 1, Entries 30, 32).

  With the optimized reaction conditions in hand, the scope of midazoles and (hetero)aryl bromides for direct arylation catalyzed was investigated in Table 2. The electronic effect of the substituents of the aryl bromides is significant. The aryl bromides bearing electron-with- drawing group, such as acetyl, cyano, aldehyde, fluoro, chloro, and nitro (Table 2, 3b~3g), had relatively higher reactivity in comparison to those with the electron-dona- ting group (Table 2, 3h, 3i). The reactivity of meta-substituted aryl bromides was also investigated, and the corresponding products were obtained in 76% yield (Table 2, 3j). The effect of the steric influence on the aryl bromides was also studied, 2-methyl bromobenzene and 1-naphthyl bromide afforded products 3k and 3l in moderate yields of 55% and 58%.

  表 2

  

  Table 2.  Direct arylation of imbazole with (hetero)aryl bromides^a

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  Encouraged by the outstanding performance of C4 in the direct arylation with imidazoles of aryl bromide, various heteroaryl bromides were investigated for direct C—H bond arylation with 1-methy-1H-imidazole. The heteroaryl bromides bearing pyridine, isoquinoline, and quinolone, reacted with 1-methy-1H-imidazole to give excellent yields (Table 2, 3m~3r). When 2-bromo-5-methylthio- phene was selected as coupling partner, the desired product of 3s was afforded in low yield of 34%, while a higher yield of 76% could be obtained when the reaction time was prolonged to 24 h. Another challenging substrate of imidazole, 1, 2-dimethyl-1H-imidazole, was examined for direct C—H arylation with aryl and heteroaryl bromides. To our delight, 1, 2-dimethyl-1H-imidazole could smoothly reacted with aryl bromides and heteroaryl bromides to give desired products in moderate to excellent yields (Table 2, 4a~4o).

  To demonstrate the scope of established protocol, we sought to evaluate the feasibility of employing palladium complex of C4 catalyzed in direct arylation reaction of thiazoles with aryl bromides and heteroaryl bromides in Table 3. To our delight, at a low catalyst loading of 0.5 mol% under 120 ℃ for 10 h using KOAc as base without PivOH as additive, 4-methyl thiazoles and 2, 4-dimethyl thiazoles were first expored in the current standard conditions. Aryl bromides bearing electron-withdrawing group and electron-donating group as well as heteroaryl bromides, such as pyridine, quinolone and thiophene, were suitable for the coupling reaction with 4-methyl thiazoles and 2, 4-dimethyl thiazoles, giving the desired products in excellent yields (Table 3, 5a~5g, 6a~6k). As for other heteroaryl substrates, such as isoxazoles and pyrazole, the direct C—H bond arylation also worked well when reaction temperature increased to 130 ℃ and/or a high palladium loading of 1 mol% was used. (Table 3, 7a~7e, 8a~8d). To the best of our knowledge, the palladium complex C4/KOAc catalytic system is the most efficient catalysts based on one-component KOAc system.^{[6, 12f~12h, 30]}

  表 3

  

  Table 3.  Direct arylation of azoles with (hetero)aryl bromides^a

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  In order to explore whether the reaction process occurs from Pd(0) to Pd(II) or from Pd(II) to Pd(IV), two control experiments were performed (Scheme 2), in which the combination of the ligand L4 with zero valence palladium sources such as Pd₂(dba)₃ and Pd(PPh₃)₄ were tested in the reaction of 1-methy-1H-imidazole with 4-bromoaceto- phenone under the optimized conditions and the product was obtained with 86% and 88% yields, respectively. The catalytic efficiency of palladium(0) sources is comparable to that of our developed palladium(II) catalytic system (Table 1, Entry 28). The results suggested that palladium(0) species is formed through the reduction of palladium(II) complex C4, which may be the active intermediate in this reaction. This is consistent with the previous reports.^{[12f, 12g]}

  Scheme 2

  

  Scheme 2.  Control experiments for reaction mechanism

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  3.   Conclusions

  In summary, a new type of carbazole-based pincer palladium complexes C1~C6 were synthesized by a simple route. The catalysts containing electron-withdrawing group at pyridine ring showed more efficient than those containing electron-donating group at pyridine ring. The C4/ KOAc catalytic system allows wide scopes of a wide range of (hetero)aryl bromides and various azoles, together with excellent functional group tolerance, affording a series of N-arylated products in good to excellent yields. It is noteworthy that the direct C—H bond arylation for thiazoles smoothly proceeds to afford the coupling products in high yields under 120 ℃ when employing KOAc as sole base, even in the presence of low palladium loading of 0.5 mol%. The C4/KOAc catalytic system is most efficient for the arylation of thiazoles in the KOAc-based system. The strategy of catalyst design would provide insight to the design and synthesis of highly active catalysts for the direct C—H bond arylation.

  4.   Experimental section

  4.1   Analytical methods

  NMR spectra were recorded on a Bruker Avance III HD 400 spectrometer using tetrame thyl silane (TMS) as an internal standard (400 MHz for ¹H NMR and 100 MHz for ¹³C NMR). Mass spectra (MS) were collected on a Bruker ultrafleXtreme mass spectrometer. Single crystal structure determination was conducted on a Bruker Smart APEX II diffractometer equipped with an APEX II CCD detector.

  4.2   Typical procedures for the synthesis of carbazole-pyridine ligand (L1)

  2-Hydroxycarbazole (0.5 mmol), 2-fluoropyridine (1 mmol) and cesium carbonate (1 mmol) were added to a 25 mL flask bottle reactor, and 4 mL of DMF was added. The reaction was carried out at 150 ℃ for 12 h. After the reaction was completed, the reaction mixture was cooled to ambient temperature and 60 mL of sodium chloride solution was added. The mixture was diluted with dichloromethane (20 mL), followed by extraction three times with dichloromethane (20 mL×3). The organic layer was evaporated under reduced pressure. The crude products were purified by silica gel column chromatography using V(petroleum ether):V(ethyl acetate)＝15:1 as eluent.^[27]

  4.3   Typical procedures for the synthesis of NCN- type Pd complex (C1)

  Carbazole-pyridine ligand (L1, 0.5 mmol) and palladium dichloride (0.5 mmol) were mixed in 3 mL of acetonitrile solvent. The reaction was carried out at 80 ℃ for 12 h. After completion of the reaction, the acetonitrile was evaporated under reduced pressure. The crude products were purified by silica gel column chromatography using V(dichloromethane):V(methanol)＝30:1 as eluent. Pure yellow solid product C1 could be got with 90% yield.

  [9-(Pyridin-2-yl)-2-(pyridin-2-yloxy)-9H-carbazole] pa- lladium chloride (C1): 214 mg, yield 90%. Yellow solid, m.p. 271.2~271.5 ℃; ¹H NMR (400 MHz, CDCl₃) δ: 9.74 (d, J＝6.0 Hz, 1H), 9.56 (d, J＝6.4 Hz, 1H), 7.96~7.91 (m, 2H), 7.84~7.77 (m, 2H), 7.75~7.71 (m, 1H), 7.62 (d, J＝8.4 Hz 1H), 7.43 (t, J＝7.6 Hz, 1H), 7.34~7.31 (m, 1H), 7.25 (d, J＝7.2 Hz, 1H), 7.04~6.96 (m, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 159.1, 155.9, 153.4, 149.7, 148.3, 141.2, 139.8, 139.6, 139.1, 128.8, 125.8, 123.6, 120.9, 120.2, 118.5, 118.4, 117.1, 115.8, 115.3, 113.1, 106.1; HRMS (MALDI) calcd for C₂₂H₁₄N₃OPd [M－Cl]⁺ 442.0172, found 442.0175.

  [9-(5-Iodopyridin-2-yl)-2-((5-iodopyridin-2-yl)oxy)-9H-carbazole] palladium chloride (C2): 327 mg, yield 90%. Yellow solid, m.p. 180.2~181.7 ℃; ¹H NMR (400 MHz, CDCl₃) δ: 10.02 (d, J＝2.0 Hz, 1H), 9.86 (d, J＝2.4 Hz, 1H), 8.07 (dd, J＝8.8, 2.4 Hz, 1H), 8.03~7.99 (m, 2H), 7.85(d, J＝8.4 Hz, 2H), 7.71 (d, J＝8.4 Hz 1H), 7.53~7.49 (m, 1H), 7.41 (t, J＝7.6 Hz, 1H), 7.09 (dd, J＝8.8, 4.8 Hz, 2H); ¹³C NMR (100 MHz, CDCl₃) δ: 160.9, 158.4, 158.2, 149.3, 149.2, 147.7, 147.5, 139.1, 138.7, 128.8, 126.0, 124.0, 121.0, 120.3, 117.3, 116.8, 115.6, 114.5, 113.1, 105.2, 82.4, 82.1; HRMS (MALDI) calcd for C₂₂H₁₂I₂N₃OPd [M－Cl]⁺ 693.8105, found 693.8102.

  [9-(5-Bromopyridin-2-yl)-2-((5-bromopyridin-2-yl)ox-y)-9H-carbazole] palladium chloride (C3): 283 mg, yield 90%. Yellow solid, m.p. 183.4~183.5 ℃; ¹H NMR (400 MHz, CDCl₃) δ: 9.20 (d, J＝2.4 Hz, 1H), 9.74 (d, J＝2.4 Hz, 1H), 8.00~7.92 (m, 3H), 7.89~7.85 (m, 2H), 7.70 (d, J＝8.0 Hz, 1H), 7.53~7.49 (m, 1H), 7.40 (t, J＝7.6 Hz, 1H), 7.21 (d, J＝8.8 Hz, 1H), 7.09 (d, J＝8.0 Hz, 1H); ¹³C NMR (100 MHz, CDCl₃) δ: 157.8, 156.1, 153.3, 149.2, 147.0, 144.0, 142.4, 139.1, 138.8, 128.7, 126.0, 123.9, 120.9, 120.3, 117.2, 116.2, 115.6, 113.9, 113.1, 112.8, 112.4, 105.3; HRMS (MALDI) calcd for C₂₂H₁₂Br₂N₃OPd [M－Cl]⁺ 597.8382, found 597.8373.

  [9-(5-Chloropyridin-2-yl)-2-((5-chloropyridin-2-yl)ox-y)-9H-carbazole] palladium chloride (C4): 245 mg, yield 91%. Yellow solid, m.p. 202.2~203.5 ℃; ¹H NMR (400 MHz, CDCl₃) δ: 9.84 (d, J＝2.4 Hz, 1H), 9.64 (d, J＝2.8 Hz, 1H), 8.03~7.99 (m, 2H), 7.86 (d, J＝8.0 Hz, 1H), 7.82 (dd, J＝8.8, 2.4 Hz, 1H), 7.77 (dd, J＝9.2, 2.8 Hz, 1H), 7.71 (d, J＝8.4 Hz, 1H), 7.53~7.49 (m, 1H), 7.41 (t, J＝7.2 Hz, 1H), 7.28 (s, 1H), 7.10 (d, J＝8.0 Hz, 1H); ¹³C NMR (100 MHz, CDCl₃) δ: 157.6, 154.0, 151.3, 149.4, 146.8, 141.4, 139.8, 139.3, 138.9, 128.8, 126.1, 125.8, 125.3, 124.0, 121.0, 120.4, 117.3, 115.8, 115.6, 113.5, 113.2, 105.6; HRMS (MALDI) calcd for C₂₂H₁₂Cl₂N₃OPd [M－Cl]⁺ 509.9392, found 511.9389.

  [9-(5-Phenylpyridin-2-yl)-2-((5-phenylpyridin-2-yl)ox-y)-9H-carbazole] palladium chloride (C5): 283.9 mg, yield 90%. Yellow solid, m.p. 190.2~190.5 ℃; ¹H NMR (400 MHz, CDCl₃) δ: 10.14 (d, J＝2.4 Hz, 1H), 9.97 (d, J＝2.4 Hz, 1H), 8.09~7.99 (m, 4H), 7.93 (d, J＝8.0 Hz, 1H), 7.71 (d, J＝8.0 Hz, 1H), 7.67~7.62 (m, 4H), 7.52~7.43 (m, 5H), 7.40~7.34 (m, 4H), 7.12 (d, J＝8.0 Hz, 1H); ¹³C NMR (100 MHz, CDCl₃) δ: 157.9, 154.1, 151.4, 149.5, 146.8, 139.7, 139.5, 139.0, 137.8, 135.8, 135.6, 131.7, 131.1, 129.2, 128.8, 128.4, 128.3, 127.0, 126.8, 125.8, 123.5, 120.8, 120.1, 117.1, 115.7, 114.9, 113.0, 112.8, 105.6; HRMS (ESI) calcd for C₃₄H₂₂N₃OPd [M－Cl]⁺594.0798, found 594.0815.

  [9-(5-Methylpyridin-2-yl)-2-((5-methylpyridin-2-yl)ox-y)-9H-carbazole] palladium chloride (C6): 230.2 mg, yield 91%. Yellow solid, m.p. 205.2~205.5 ℃; ¹H NMR (400 MHz, CDCl₃) δ: 9.55 (d, J＝14.0 Hz, 1H), 9.38 (d, J＝8.0 Hz, 1H), 7.95~7.73 (m, 3H), 7.64~7.41 (m, 4H), 7.35~7.29 (m, 1H), 7.16~7.09 (m, 1H), 7.02~6.94 (m, 1H), 2.29 (m, 6H); ¹³C NMR (100 MHz, CDCl₃) δ: 157.4, 155.1, 152.3, 149.9, 146.2, 142.3, 140.7, 139.7, 139.0, 128.6, 128.1, 128.0, 125.6, 123.2, 120.7, 119.8, 116.9, 115.5, 114.4, 112.8, 112.3, 106.2, 17.7, 17.6; HRMS (ESI) calcd for C₂₄H₁₈N₃OPd [M－Cl]⁺ 470.0485, found 470.0487.

  4.4   General procedures for direct arylation

  The direct C—H activation arylation reactions were carried out in the air. (Hetero)aryl bromide (1.0 mmol), azoles (2.0 mmol), carbazole-palladium complexes (0.5~1.5 mol%), base (2 mmol), and 3 mL of solvent were added into a 25 mL flask bottle reactor. The reaction was carried out at 120~140 ℃ for 10~12 h. Then, the mixture was cooled to room temperature and 60 mL of sodium chloride solution was added. The mixture was diluted with dichloromethane (20 mL), followed by extraction three times with dichloromethane (20 mL×3). The organic layer was dried with anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude products were purified by silica gel column chromatography using ethyl acetate as eluent. The isolated yield of product was obtained based on the amount of (hetero)aryl bromide.

  1-Methyl-5-phenyl-1H-imidazole (3a):^{[12d] 1}H NMR (400 MHz, CDCl₃) δ: 7.48 (s, ArH, 1H), 7.42~7.31 (m, ArH, 5H), 7.07 (s, ArH, 1H), 3.62 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 139.1, 133.5, 129.8, 128.7, 128.5, 128.1, 127.9, 32.5.

  1-[4-(1-Methyl-1H-imidazol-5-yl)phenyl]ethan-1-one(3b):^{[12d] 1}H NMR (400 MHz, CDCl₃) δ: 8.00 (d, J＝8.4 Hz, ArH, 2H), 7.55 (s, ArH, 1H), 7.49 (d, J＝8.8 Hz, ArH, 2H), 7.19 (s, ArH, 1H), 3.71 (s, C(O)CH₃, 3H), 2.61 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 197.4, 140.2, 136.1, 134.4, 132.4, 129.3, 128.8, 128.0, 32.9, 26.6.

  5-(4-Chlorophenyl)-1-methyl-1H-imidazole (3c):^[6b]1H NMR (400 MHz, CDCl₃) δ: 7.42 (s, ArH, 1H), 7.32~7.29 (m, ArH, 2H), 7.23~7.21 (m, ArH, 2H), 7.00 (s, ArH, 1H), 3.56 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 139.4, 133.9, 132.3, 129.6, 129.0, 128.3, 128.3, 32.5.

  4-(1-Methyl-1H-imidazol-5-yl)benzonitrile (3d):^[6c]1H NMR (400 MHz, CDCl₃) δ: 7.71 (d, J＝8.4 Hz, ArH, 2H), 7.56 (s, ArH, 1H), 7.51 (d, J＝8.8 Hz, ArH, 2H), 7.20 (s, CH₃, 1H), 3.72 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 140.5, 134.4, 132.6, 131.7, 129.8, 128.3, 118.6, 111.3, 32.9.

  4-(1-Methyl-1H-imidazol-5-yl)benzaldehyde (3e):^{[12d] 1}H NMR (400 MHz, CDCl₃) δ: 9.89 (d, J＝6.8 Hz, CHO, 1H), 7.80 (d, J＝8.4 Hz, ArH, 2H), 7.46~7.44 (m, ArH, 3H), 7.10 (s, ArH, 1H), 3.63 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 191.5, 140.4, 135.7, 135.2, 132.2, 130.1, 129.6, 128.1, 33.0.

  1-Methyl-5-(4-nitrophenyl)-1H-imidazole (3f):^[31]1H NMR (400 MHz, CDCl₃) δ: 8.30 (d, J＝8.8 Hz, ArH, 2H), 7.61~7.56 (m, ArH, 3H), 7.27 (s, ArH, 1H), 3.76 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 147.0, 140.9, 136.3, 131.4, 130.3, 128.3, 124.2, 33.1.

  5-(4-Fluorophenyl)-1-methyl-1H-imidazole (3g):^[32]1H NMR (400 MHz, CDCl₃) δ: 7.48 (s, ArH, 1H), 7.35~7.30 (m, ArH, 2H), 7.13~7.07 (m, ArH, 2H), 7.03 (s, ArH, 1H), 3.60 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 163.8, 161.3, 139.0, 132.5, 130.4 (d, J＝8.2 Hz), 128.1, 125.9 (d, J＝3.3 Hz), 115.9, 115.7, 32.4; ¹⁹F NMR (376 MHz, CDCl₃) δ: －113.62.

  1-Methyl-5-(p-tolyl)-1H-imidazole (3h):^{[6c] 1}H NMR (400 MHz, CDCl₃) δ: 7.43 (s, ArH, 1H), 7.22 (d, J＝8.0 Hz, ArH, 2H), 7.18 (d, J＝8.4 Hz, ArH, 2H), 7.01 (s, ArH, 1H), 3.57 (s, CH₃, 3H), 2.33 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 138.8, 137.7, 133.3, 129.3, 128.3, 127.6, 126.8, 32.3, 21.1.

  5-(4-Methoxyphenyl)-1-methyl-1H-imidazole (3i):^[6c]1H NMR (400 MHz, CDCl₃) δ: 7.51 (s, ArH, 1H), 7.30 (d, J＝8.8 Hz, ArH, 2H), 7.03 (s, ArH, 1H), 6.96 (d, J＝8.8 Hz, ArH, 2H), 3.84 (s, OCH₃, 3H), 3.62 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 159.5, 138.6, 133.3, 130.0, 127.5, 122.2, 114.2, 55.4, 32.4.

  1-Methyl-5-(m-tolyl)-1H-imidazole (3j): ¹H NMR (400 MHz, CDCl₃) δ: 7.45 (s, ArH, 1H), 7.29~7.25 (m, ArH, 1H), 7.16~7.13 (m, ArH, 3H), 7.04 (s, ArH, 1H), 3.60 (s, CH₃, 3H), 2.35 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 138.9, 138.4, 133.5, 129.7, 129.1, 128.6, 128.5, 127.9, 125.4, 32.5, 21.4; HRMS (ESI) calcd for C₁₁H₁₃N₂ [M+H]⁺ 173.1073, found 173.1075.

  1-Methyl-5-(o-tolyl)-1H-imidazole (3k):^{[12c] 1}H NMR (400 MHz, CDCl₃) δ: 7.54 (s, ArH, 1H), 7.31~7.27 (m, ArH, 2H), 7.23~7.18 (m, ArH, 2H), 6.97 (s, ArH, 1H), 3.41 (s, CH₃, 3H), 2.18 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 138.3, 138.0, 132.1, 131.1, 130.3, 129.2, 128.9, 128.2, 125.7, 31.7, 20.0.

  1-Methyl-5-(naphthalen-1-yl)-1H-imidazole (3l):^[33]1H NMR (400 MHz, CDCl₃) δ: 7.91~7.88 (m, ArH, 2H), 7.64 (d, J＝7.6 Hz, ArH, 2H), 7.53~7.41 (m, ArH, 4H), 7.15 (s, ArH, 1H), 3.38 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 138.5, 133.7, 132.9, 131.2, 129.4, 129.3, 129.1, 128.4, 127.2, 126.8, 126.2, 125.5, 125.3, 32.0.

  3-(1-Methyl-1H-imidazol-5-yl)pyridine (3m):^{[11c] 1}H NMR (400 MHz, CDCl₃) δ: 8.54~8.51 (m, ArH, 1H), 8.47~8.43 (m, ArH, 1H), 7.59~7.55 (m, ArH, 1H), 7.43 (d, J＝8.4 Hz, ArH, 1H), 7.25~7.21 (m, ArH, 1H), 7.02 (d, J＝9.2 Hz, ArH, 1H), 3.54 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 148.9, 139.9, 135.4, 130.0, 128.9, 125.9, 123.5, 123.4, 32.6.

  2-Fluoro-5-(1-methyl-1H-imidazol-5-yl)pyridine (3n): ¹H NMR (400 MHz, CDCl₃) δ: 8.25 (d, J＝2.4 Hz, ArH, 1H), 7.83~7.78 (m, ArH, 1H), 7.63 (s, ArH, 1H), 7.14 (s, ArH, 1H), 7.02 (dd, J＝8.4, 3.2 Hz, ArH, 1H), 3.66 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 164.4, 162.0, 147.1 (d, J＝14.9 Hz), 141.1 (d, J＝8.0 Hz), 139.8, 128.9, 123.9 (d, J＝4.7 Hz), 109.8 (d, J＝37.5 Hz), 32.5; ¹⁹F NMR (376 MHz, CDCl₃) δ: －68.24; HRMS (ESI) calcd for C₉H₉FN₃ [M+H]⁺ 178.0775, found 178.0781.

  2-Chloro-5-(1-methyl-1H-imidazol-5-yl)pyridine(3o):^[34]1H NMR (400 MHz, CDCl₃) δ: 8.32 (s, ArH, 1H), 7.60 (d, J＝8.4 Hz, ArH, 1H), 7.47 (s, ArH, 1H), 7.30 (d, J＝8.4 Hz, ArH, 1H), 7.06 (s, ArH, 1H), 3.60 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 150.6, 148.5, 140.2, 138.1, 129.4, 128.7, 124.9, 124.3, 32.6.

  2-Methyl-5-(1-methyl-1H-imidazol-5-yl)pyridine (3p):^{[12e] 1}H NMR (400 MHz, CDCl₃) δ: 8.45 (d, J＝7.2 Hz, ArH, 1H), 7.53~7.44 (m, ArH, 2H), 7.14 (t, J＝8.4 Hz, ArH, 1H), 7.03 (d, J＝9.2 Hz, ArH, 1H), 3.58 (s, CH₃, 3H), 2.52 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 158.0, 148.4, 139.6, 136.0, 130.1, 128.7, 123.1, 123.0, 32.5, 24.2.

  4-(1-Methyl-1H-imidazol-5-yl)isoquinoline (3q):^{[13c] 1}H NMR (400 MHz, CDCl₃) δ: 9.26 (s, ArH, 1H), 8.44 (s, ArH, 1H), 8.01 (d, J＝8.0 Hz, ArH, 1H), 7.67~7.59 (m, ArH, 4H), 7.17 (s, ArH, 1H), 3.43 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 153.4, 144.6, 139.4, 135.4, 131.3, 130.5, 128.4, 128.1, 127.7, 124.4, 121.1, 32.2.

  3-(1-Methyl-1H-imidazol-5-yl)quinolone (3r):^[31]1H NMR (400 MHz, CDCl₃) δ: 8.91 (d, J＝2.4 Hz, ArH, 1H), 8.08~8.06 (m, ArH, 2H), 7.78 (d, J＝8.0 Hz, ArH, 1H), 7.69~7.66 (m, ArH, 1H), 7.56~7.51 (m, ArH, 2H), 7.22 (s, ArH, 1H), 3.68 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 150.0, 147.2, 139.9, 134.2, 129.8, 129.3, 129.3, 127.8, 127.5, 127.3, 123.7, 123.0, 32.7.

  1-Methyl-5-(5-methylthiophen-2-yl)-1H-imidazole (3s):^{[12e] 1}H NMR (400 MHz, CDCl₃) δ: 7.48 (s, ArH, 1H), 7.12 (s, ArH, 1H), 6.86 (dd, J＝3.6, 1.6 Hz, ArH, 1H), 6.74~6.73 (m, ArH, 1H), 3.68 (s, CH₃, 3H), 2.50 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 140.7, 139.0, 128.9, 128.2, 127.1, 126.3, 125.7, 32.6, 15.2.

  5-(4-Chlorophenyl)-1, 2-dimethyl-1H-imidazole (4a):^{[12d] 1}H NMR (400 MHz, CDCl₃) δ: 7.31 (d, J＝8.4 Hz, ArH, 2H), 7.20 (d, J＝8.8 Hz, ArH, 2H), 6.87 (s, ArH, 1H), 3.43 (s, CH₃, 3H), 2.36 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 146.3, 133.6, 132.4, 129.8, 129.1, 128.9, 126.2, 31.3, 13.7.

  1-[4-(1, 2-Dimethyl-1H-imidazol-5-yl)phenyl]ethan-1-one (4b):^{[12d] 1}H NMR (400 MHz, CDCl₃) δ: 7.98 (d, J＝8.8 Hz, ArH, 2H), 7.43 (d, J＝8.4 Hz, ArH, 2H), 7.03 (s, ArH, 1H), 3.55 (s, CH₃, 3H), 2.59 (s, CH₃, 3H), 2.43 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 197.4, 147.2, 135.8, 135.1, 132.6, 128.8, 128.0, 127.1, 31.7, 26.6, 13.7.

  4-(1, 2-Dimethyl-1H-imidazol-5-yl)benzonitrile (4c):^{[12d] 1}H NMR (400 MHz, CDCl₃) δ: 7.70 (d, J＝8.4 Hz, ArH, 2H), 7.46 (d, J＝8.8 Hz, ArH, 2H), 7.06 (s, ArH, 1H), 3.57 (s, CH₃, 3H), 2.46 (s, CH3, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 147.7, 135.1, 132.6, 131.9, 128.3, 127.8, 118.7, 110.9, 31.7, 13.8.

  4-(1, 2-dimethyl-1H-imidazol-5-yl)benzaldehyde (4d):^{[12d] 1}H NMR (400 MHz, CDCl₃) δ: 10.01 (s, CHO, 1H), 7.93~7.90 (m, ArH, 2H), 7.52 (d, J＝8.4 Hz, ArH, 2H), 7.08 (s, ArH, 1H), 3.59 (s, CH₃, 3H), 2.46 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 191.5, 147.6, 136.5, 135.0, 132.5, 130.2, 128.3, 127.8, 31.8, 13.8.

  1, 2-dimethyl-5-(4-nitrophenyl)-1H-imidazole (4e):^[6c]1H NMR (400 MHz, CDCl₃) δ: 8.27 (d, J＝8.8 Hz, ArH, 2H), 7.52 (d, J＝8.8 Hz, ArH, 2H), 7.12 (s, ArH, 1H), 3.61 (s, CH₃, 3H), 2.47 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 148.1, 146.7, 137.0, 131.6, 128.4, 128.2, 124.2, 31.8, 13.8.

  1, 2-Dimethyl-5-(p-tolyl)-1H-imidazole (4f):^[6c]1H NMR (400 MHz, CDCl₃) δ: 7.22 (s, ArH, 4H), 6.91 (s, ArH, 1H), 3.48 (s, CH₃, 3H), 2.42 (s, CH₃, 3H), 2.37 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 145.7, 137.5, 133.6, 129.4, 128.6, 127.7, 125.6, 31.3, 21.2, 13.8.

  1, 2-Dimethyl-5-(m-tolyl)-1H-imidazole (4g): ¹H NMR (400 MHz, CDCl₃) δ: 7.29~7.25 (m, ArH, 1H), 7.14~7.11 (m, ArH, 3H), 6.91 (d, J＝1.6 Hz, ArH, 1H), 3.48 (s, CH₃, 3H), 2.41 (s, CH₃, 3H), 2.36 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 145.8, 138.4, 133.7, 130.5, 129.3, 128.5, 128.4, 125.8, 125.6, 31.3, 21.5, 13.7; HRMS (ESI) calcd for C₁₂H₁₅N₂ [M+H]⁺ 187.1230, found 187.1229.

  1, 2-Dimethyl-5-(naphthalen-1-yl)-1H-imidazole (4h):^{[35] 1}H NMR (400 MHz, CDCl₃) δ: 7.91~7.89 (m, ArH, 2H), 7.68 (d, J＝8.4 Hz, ArH, 1H), 7.54~7.41 (m, ArH, 4H), 7.02 (s, ArH, 1H), 3.27 (s, CH₃, 3H), 2.50 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 145.5, 133.7, 133.0, 131.1, 129.1, 129.0, 128.4, 128.1, 127.2, 126.7, 126.1, 125.7, 125.3, 31.0, 13.8.

  3-(1, 2-Dimethyl-1H-imidazol-5-yl)pyridine (4i):^[6c]1H NMR (400 MHz, CDCl₃) δ: 8.88~8.85 (m, ArH, 1H), 8.83~8.79 (m, ArH, 1H), 7.93~7.88 (m, ArH, 1H), 7.62~7.57 (m, ArH, 1H), 7.25 (d, J＝8.4 Hz, ArH, 1H), 3.77 (s, CH₃, 3H), 2.68 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 149.1, 148.6, 146.9, 135.5, 130.0, 127.0, 126.6, 123.4, 31.3, 13.7.

  5-(1, 2-Dimethyl-1H-imidazol-5-yl)-2-fluoropyridine(4j):^{[12e] 1}H NMR (400 MHz, CDCl₃) δ: 8.21 (d, J＝2.4 Hz, ArH, 1H), 7.78~7.74 (m, ArH, 1H), 7.02~6.99 (m, ArH, 2H), 3.50 (s, CH₃, 3H), 2.45 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 164.2 (d, J＝239.4 Hz), 147.2, 147.0 (d, J＝9.5 Hz), 141.2 (d, J＝8.1 Hz), 128.8, 127.1, 124.8 (d, J＝4.7 Hz), 109.9 (d, J＝37.4 Hz), 31.3, 13.7; ¹⁹F NMR (376 MHz, CDCl₃) δ: －68.72.

  2-Chloro-5-(1, 2-dimethyl-1H-imidazol-5-yl)pyridine(4k):^{[12e] 1}H NMR (400 MHz, CDCl₃) δ: 8.38 (dd, J＝2.4, 0.8 Hz, ArH, 1H), 7.62 (dd, J＝8.4, 2.8 Hz, ArH, 1H), 7.37 (dd, J＝8.4, 0.8 Hz, ArH, 1H), 7.00 (s, ArH, 1H), 3.51 (s, CH₃, 3H), 2.44 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 150.5, 148.7, 147.3, 138.3, 128.8, 127.4, 125.6, 124.3, 31.4, 13.7.

  4-(1, 2-Dimethyl-1H-imidazol-5-yl)isoquinoline (4l):^[6c]1H NMR (400 MHz, CDCl₃) δ: 9.26 (s, ArH, 1H), 8.44 (s, ArH, 1H), 8.02 (d, J＝8.0 Hz, ArH, 1H), 7.70~7.61 (m, ArH, 3H), 7.05 (s, ArH, 1H), 3.31 (s, CH₃, 3H), 2.49 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 153.2, 146.5, 144.7, 135.5, 131.2, 128.4, 128.4, 128.1, 127.7, 124.6, 121.9, 31.2, 13.8.

  3-(1, 2-Dimethyl-1H-imidazol-5-yl)quinolone (4m):^[35]1H NMR (400 MHz, CDCl₃) δ: 9.05 (d, J＝2.0 Hz, ArH, 1H), 8.23 (d, J＝8.0 Hz, ArH, 1H), 8.17 (s, ArH, 1H), 7.93 (d, J＝8.0 Hz, ArH, 1H), 7.83~7.80 (m, ArH, 1H), 7.69~7.65 (m, ArH, 1H), 7.26 (s, ArH, 1H), 3.69 (s, CH₃, 3H), 2.59 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 150.0, 146.8, 133.7, 130.0, 129.4, 129.0, 127.7, 127.4, 127.1, 127.0, 123.6, 31.3, 13.5.

  1, 2-Dimethyl-5-(thiophen-2-yl)-1H-imidazole (4n):^[31]1H NMR (400 MHz, CDCl₃) δ: 7.31 (dd, J＝5.2, 1.2 Hz, ArH, 1H), 7.07 (dd, J＝5.2, 3.6 Hz, ArH, 1H), 7.02~7.01 (m, ArH, 2H), 3.54 (s, CH₃, 3H), 2.41 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 146.3, 131.4, 127.5, 127.2, 126.2, 125.8, 124.7, 31.2, 13.7.

  1, 2-Dimethyl-5-(5-methylthiophen-2-yl)-1H-imidazole(4o):^{[12e] 1}H NMR (400 MHz, CDCl₃) δ: 6.95 (s, ArH, 1H), 6.79: (d, J＝3.2 Hz, ArH, 1H), 6.71~6.70 (m, ArH, 1H), 3.52 (s, CH₃, 3H), 2.47 (s, CH₃, 3H), 2.39 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 146.0, 140.5, 129.0, 126.9, 126.8, 126.3, 125.6, 31.2, 15.2, 13.7.

  1-(4-(4-Methylthiazol-5-yl)phenyl)ethan-1-one (5a):^{[36] 1}H NMR (400 MHz, CDCl₃) δ: 8.61 (s, ArH, 1H), 7.88 (d, J＝8.4 Hz, ArH, 2H), 7.41 (d, J＝8.4 Hz, ArH, 2H), 2.50 (s, CH₃, 3H), 2.45 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 197.2, 151.1, 149.5, 136.8, 136.1, 130.8, 129.2, 128.7, 26.6, 16.4.

  4-(4-Methylthiazol-5-yl)benzonitrile (5b):^[36]1H NMR (400 MHz, CDCl₃) δ: 8.75 (s, ArH, 1H), 7.71 (d, J＝8.4 Hz, ArH, 2H), 7.55 (d, J＝8.8 Hz, ArH, 2H), 2.56 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 151.6, 150.1, 136.9, 132.5, 130.1, 129.7, 118.5, 111.5, 16.4.

  4-Methyl-5-(p-tolyl)thiazole (5c):^{[37] 1}H NMR (400 MHz, CDCl₃) δ: 8.65 (s, ArH, 1H), 7.33 (d, J＝8.4 Hz, ArH, 2H), 7.23 (d, J＝8.0 Hz, ArH, 2H), 2.53 (s, CH₃, 3H), 2.39 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 150.0, 148.2, 137.9, 132.0, 129.4, 129.2, 129.0, 21.2, 16.1.

  4-Methyl-5-(pyridin-3-yl)thiazole (5d):^{[13b] 1}H NMR (400 MHz, CDCl₃) δ: 8.72 (s, ArH, 1H), 8.68 (d, J＝1.6 Hz, ArH, 1H), 8.56 (dd, J＝4.8, 1.6 Hz, ArH, 1H), 7.73~7.70 (m, ArH, 1H), 7.35~7.31 (m, ArH, 1H), 2.51 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 151.3, 149.8, 149.8, 149.0, 136.4, 128.3, 128.1, 123.4, 16.0.

  5-(6-Chloropyridin-3-yl)-4-methylthiazole (5e):^{[13b] 1}H NMR (400 MHz, CDCl₃) δ: 8.69 (s, ArH, 1H), 8.39 (d, J＝2.4 Hz, ArH, 1H), 7.64 (dd, J＝8.0, 2.4 Hz, ArH, 1H), 7.32 (d, J＝8.4 Hz, ArH, 1H), 2.45 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 151.5, 150.8, 150.2, 149.4, 139.0, 127.2, 126.7, 124.2, 16.0.

  4-Methyl-5-(6-methylpyridin-3-yl)thiazole (5f):^{[13b] 1}H NMR (400 MHz, CDCl₃) δ: 8.69 (s, ArH, 1H), 8.55 (d, J＝2.0 Hz, ArH, 1H), 7.60 (dd, J＝8.0, 2.4 Hz, ArH, 1H), 7.19 (d, J＝8.0 Hz, ArH, 1H), 2.57 (s, CH₃, 3H), 2.49 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 158.0, 150.9, 149.5, 149.0, 136.8, 128.2, 125.2, 123.1, 24.2, 15.9.

  4-Methyl-5-(5-methylthiophen-2-yl)thiazole (5g):^{[13b] 1}H NMR (400 MHz, CDCl₃) δ: 8.57 (s, ArH, 1H), 6.93 (d, J＝3.6 Hz, ArH, 1H), 6.72 (d, J＝3.6 Hz, ArH, 1H), 2.59 (s, CH₃, 3H), 2.50 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 149.5, 148.4, 141.0, 130.8, 127.1, 126.0, 125.9, 16.5, 15.3.

  1-[4-(2, 4-Dimethylthiazol-5-yl)phenyl]ethan-1-one (6a):^{[13a] 1}H NMR (400 MHz, CDCl₃) δ: 7.99~7.96 (m, ArH, 2H), 7.51~7.48 (m, ArH, 2H), 2.69 (s, CH₃, 3H), 2.61 (s, CH₃, 3H), 2.49 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 197.3, 164.3, 148.3, 137.2, 135.8, 130.3, 129.0, 128.7, 26.6, 19.2, 16.4.

  4-(2, 4-Dimethylthiazol-5-yl)benzaldehyde (6b):^[36]1H NMR (400 MHz, CDCl₃) δ: 10.01 (s, CHO, 1H), 7.90 (d, J＝8.4 Hz, ArH, 2H), 7.56 (d, J＝8.0 Hz, ArH, 2H), 2.69 (s, CH₃, 3H), 2.49 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 191.5, 164.7, 148.6, 138.6, 135.1, 130.2, 130.0, 129.4, 19.2, 16.4.

  4-(2, 4-Dimethylthiazol-5-yl)benzonitrile (6c):^[36]1H NMR (400 MHz, CDCl₃) δ: 7.67 (d, J＝8.4 Hz, ArH, 2H), 7.49 (d, J＝8.0 Hz, ArH, 2H), 2.68 (s, CH₃, 3H), 2.46 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 164.8, 148.8, 137.2, 132.4, 129.5, 129.4, 118.6, 111.0, 19.2, 16.4.

  2, 4-Dimethyl-5-(p-tolyl)thiazole (6d):^[36]1H NMR (400 MHz, CDCl₃) δ: 7.30 (d, J＝8.0 Hz, ArH, 2H), 7.21 (d, J＝8.0 Hz, ArH, 2H), 2.68 (s, CH₃, 3H), 2.44 (s, CH₃, 3H), 2.38 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 162.9, 146.7, 137.5, 131.4, 129.4, 129.3, 129.0, 21.2, 19.1, 16.0.

  2, 4-Dimethyl-5-(m-tolyl)thiazole (6e):^{[13a] 1}H NMR (400 MHz, CDCl₃) δ: 7.31~7.27 (m, ArH, 1H), 7.20 (d, J＝7.2 Hz, ArH, 2H), 7.13 (d, J＝7.6 Hz, ArH, 1H), 2.68 (s, CH₃, 3H), 2.45 (s, CH₃, 3H), 2.38 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 163.1, 146.9, 138.3, 132.2, 131.5, 129.9, 128.5, 128.4, 126.2, 21.4, 19.1, 16.1.

  5-(6-Chloropyridin-3-yl)-2, 4-dimethylthiazole (6f): ¹H NMR (400 MHz, CDCl₃) δ: 8.37 (d, J＝2.4 Hz, ArH, 1H), 7.61 (dd, J＝8.0, 2.4 Hz, ArH, 1H), 7.31 (d, J＝8.0 Hz, ArH, 1H), 2.63 (s, CH₃, 3H), 2.38 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 164.7, 150.4, 149.3, 148.8, 138.8, 127.6, 126.1, 124.1, 19.2, 16.0.

  2, 4-Dimethyl-5-(quinolin-3-yl)thiazole (6g): ¹H NMR (400 MHz, CDCl₃) δ 8.96 (d, J＝2.4 Hz, ArH, 1H), 8.13~8.10 (m, ArH, 2H), 7.82 (dd, J＝8.4, 1.2 Hz, ArH, 1H), 7.74~7.70 (m, ArH, 1H), 7.59~7.55 (m, ArH, 1H), 2.71 (s, CH₃, 3H), 2.51 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 164.5, 150.6, 148.7, 147.0, 135.3, 129.9, 129.3, 127.8, 127.7, 127.6, 127.4, 125.8, 19.2, 16.1.

  2, 4-Dimethyl-5-(pyridin-3-yl)thiazole (6h):^{[13b] 1}H NMR (400 MHz, CDCl₃) δ: 8.64~8.61 (m, ArH, 1H), 8.53~8.50 (m, ArH, 1H), 7.68~7.63 (m, ArH, 1H), 7.32~7.25 (m, ArH, 1H), 2.66 (s, CH₃, 3H), 2.42 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 164.3, 149.6, 148.6, 148.4, 136.1, 128.6, 127.4, 123.3, 19.1, 16.0.

  2, 4-Dimethyl-5-(6-methylpyridin-3-yl)thiazole (6i): ¹H NMR (400 MHz, CDCl₃) δ: 8.54 (d, J＝2.0 Hz, ArH, 1H), 7.59 (dd, J＝8.0, 2.4 Hz, ArH, 1H), 7.19 (d, J＝8.0 Hz, ArH, 1H), 2.68 (s, CH₃, 3H), 2.58 (s, CH₃, 3H), 2.43 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 164, 0, 157.6, 148.9, 148.1, 136.6, 127.6, 125.6, 123.0, 24.2, 19.2, 15.9; HRMS (ESI) calcd for C₁₁H₁₂N₂S [M+H]⁺ 205.0794, found 205.0802.

  2, 4-Dimethyl-5-(thiophen-2-yl)thiazole (6j):^{[13b] 1}H NMR (400 MHz, CDCl₃) δ: 7.31~7.30 (m, ArH, 1H), 7.08~7.04 (m, ArH, 2H), 2.65 (s, CH₃, 3H), 2.52 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 163.0, 147.8, 133.7, 127.5, 126.6, 125.7, 124.9, 19.1, 16.5.

  2, 4-Dimethyl-5-(5-methylthiophen-2-yl)thiazole(6k):^{[13b] 1}H NMR (400 MHz, CDCl₃) δ: 6.85 (d, J＝3.6 Hz, ArH, 1H), 6.70~6.69 (m, ArH, 1H), 2.64 (s, CH₃, 3H), 2.50 (s, CH₃, 6H); ¹³C NMR (100 MHz, CDCl₃) δ: 162.6, 147.1, 140.4, 131.3, 126.6, 125.7, 125.3, 19.0, 16.4, 15.3.

  1-[4-(3, 5-Dimethylisoxazol-4-yl)phenyl]ethan-1-one(7a):^[38]1H NMR (400 MHz, CDCl₃) δ: 7.99~7.97 (m, ArH, 2H), 7.32 (d, J＝8.4 Hz, ArH, 2H), 2.57 (s, CH₃, 3H), 2.37 (s, CH₃, 3H), 2.23 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 197.3, 165.8, 158.2, 136.0, 135.4, 129.0, 128.8, 115.8, 26.6, 11.6, 10.8.

  4-(3, 5-Dimethylisoxazol-4-yl)benzonitrile (7b):^[39]1H NMR (400 MHz, CDCl₃) δ: 7.74 (d, J＝8.8 Hz, ArH, 2H), 7.38 (d, J＝8.4 Hz, ArH, 2H), 2.43 (s, CH₃, 3H), 2.28 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 166.1, 158.1, 135.5, 132.6, 129.6, 118.5, 115.4, 111.4, 11.7, 10.9.

  3, 5-Dimethyl-4-(p-tolyl)isoxazole (7c):^[40]1H NMR (400 MHz, CDCl₃) δ: 7.18 (d, J＝8.4 Hz, ArH, 2H), 7.07 (d, J＝8.0 Hz, ArH, 2H), 2.32 (s, CH₃, 6H), 2.19 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 164.0, 157.8, 136.3, 128.5, 127.9, 126.4, 115.5, 20.2, 10.5, 9.8.

  3, 5-Dimethyl-4-(6-methylpyridin-3-yl)isoxazole(7d):^{[12e] 1}H NMR (400 MHz, CDCl₃) δ: 8.35 (s, ArH, 1H), 7.43 (dd, J＝8.0, 2.0 Hz, ArH, 1H), 7.19 (d, J＝8.0 Hz, ArH, 1H), 2.54 (s, CH₃, 3H), 2.34 (s, CH₃, 3H), 2.20 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 165.8, 158.6, 157.6, 149.1, 136.6, 123.4, 123.2, 113.4, 24.2, 11.5, 10.7.

  4-(6-Chloropyridin-3-yl)-3, 5-dimethylisoxazole (7e):^{[12e] 1}H NMR (400 MHz, CDCl₃) δ: 8.30 (d, J＝2.4 Hz, ArH, 1H), 7.55 (dd, J＝8.0, 2.4 Hz, ArH, 1H), 7.41 (d, J＝8.4 Hz, ArH, 1H), 2.41 (s, CH₃, 3H), 2.26 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 166.3, 158.3, 150.7, 149.6, 139.0, 125.5, 124.5, 112.4, 11.6, 10.7.

  1-[4-(4-Bromo-1-methyl-1H-pyrazol-5-yl)phenyl]ethan-1-one (8a):^{[12e] 1}H NMR (400 MHz, CDCl₃) δ: 8.05 (d, J＝8.4 Hz, ArH, 2H), 7.50 (d, J＝6.8 Hz, ArH, 3H), 3.80 (s, CH₃, 3H), 2.62 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 197.3, 140.1, 139.5, 137.3, 133.0, 130.0, 128.6, 93.9, 38.5, 26.7.

  4-(4-Bromo-1-methyl-1H-pyrazol-5-yl)benzonitrile (8b):^{[30b] 1}H NMR (400 MHz, CDCl₃) δ: 7.80 (d, J＝8.4 Hz, ArH, 2H), 7.55 (d, J＝7.2 Hz, ArH, 3H), 3.83 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 139.6, 139.3, 133.0, 132.5, 130.5, 118.2, 113.1, 94.2, 38.6.

  4-Bromo-1-methyl-5-(p-tolyl)-1H-pyrazole (8c): ¹H NMR (400 MHz, CDCl₃) δ: 7.52 (s, ArH, 1H), 7.32~7.28 (m, ArH, 4H), 3.80 (s, CH₃, 3H), 2.43 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 141.3, 139.3, 139.1, 129.7, 129.5, 125.4, 93.3, 38.3, 21.4.

  3-(4-Bromo-1-methyl-1H-pyrazol-5-yl)pyridine (8d):^{[30b] 1}H NMR (400 MHz, CDCl₃) δ: 8.71 (d, J＝9.6 Hz, ArH, 2H), 7.79 (d, J＝8.0 Hz, ArH, 1H), 7.57 (s, ArH, 1H), 7.48 (dd, J＝7.6, 4.8 Hz, ArH, 1H), 3.85 (s, CH₃, 3H); ¹³C NMR (100 MHz, CDCl₃) δ: 150.2, 139.5, 138.0, 137.3, 124.9, 123.6, 94.4, 38.5.

  Supporting Information The single crystal structure data of the palladium complex C1 (CCDC 1934922). The ¹H NMR and ¹³C NMR spectra of substrates and palladium complexes. The Supporting Information is available free of charge via the Internet at http://sioc-journal.cn/.

  
  
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  Scheme 1  Synthesis of carbazole-based palladium complexes C1~C6

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  Figure 1  X-ray structure of palladium complex C1

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  Scheme 2  Control experiments for reaction mechanism

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  Table 1.  Optimization of conditions for direct arylation reaction^a

  Entry	Cat. (mol%)	Solvent	Base	Temp./℃	Time/h	Yield/%
  1	C1 (2)	DMA	KOAc	140	10	75
  2	C2 (2)	DMA	KOAc	140	10	86
  3	C3 (2)	DMA	KOAc	140	10	82
  4	C4 (2)	DMA	KOAc	140	10	87
  5	C5 (2)	DMA	KOAc	140	10	84
  6	C6 (2)	DMA	KOAc	140	10	65
  7	Pd(OAc)2 (2)	DMA	KOAc	140	10	60
  8	PdCl2 (2)	DMA	KOAc	140	10	46
  9	Pd(OAc)2/PCy3 (2)	DMA	KOAc	140	10	53
  10	Pd(OAc)2/PPh3 (2)	DMA	KOAc	140	10	52
  11	PdCl2/Phth (2)	DMA	KOAc	140	10	31
  12	PdCl2/Bipy (2)	DMA	KOAc	140	10	64
  14	C4 (2)	DMA	K2CO3	140	10	35
  15	C4 (2)	DMA	K3PO4	140	10	52
  16	C4 (2)	DMA	KF	140	10	46
  17	C4 (2)	DMA	KOtBu	140	10	Trace
  18	C4 (2)	DMA	LiOtBu	140	10	Trace
  19	C4 (2)	DMA	CsF	140	10	40
  20	C4 (2)	DMA	Cs2CO3	140	10	20
  21	C4 (2)	DMF	KOAc	140	10	30
  22	C4 (2)	DMSO	KOAc	140	10	60
  23	C4 (2)	NMP	KOAc	140	10	83
  24	C4 (2)	Toluene	KOAc	140	10	Trace
  25	C4 (2)	Dioxane	KOAc	140	10	Trace
  26	C4 (2)	EG	KOAc	140	10	10
  27	C4 (2)	DMA	KOAc	140	12	94
  28	C4 (1.5)	DMA	KOAc	140	12	93
  29	C4 (1)	DMA	KOAc	140	12	76
  30	C4 (1.5)	DMA	KOAc	130	12	75
  31	C4 (1.5)	DMA	KOAc	120	12	43
  32b	C4 (1.5)	DMA	K2CO3	130	12	74
  a Reaction conditions: 4-bromoacetophenone (1.0 mmol), 1-methyl-1H-imidazole (2.0 mmol), catalyst (amount as indicated in this table), base (2.0 mmol), solvent (3.0 mL), under aerobic condition, isolated yield. b PivOH (0.3 mmol). Abbreviations: DMA, N, N-dimethylacetamide; DMF, N, N-dimethylformamide; DMSO, dimethyl sulfoxide; NMP, N-methyl-2-pyrrolidone; EG, Ethylene glycol; Phth, 1, 10-phenanthroline; Bipy, bipyridine.

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  Table 2.  Direct arylation of imbazole with (hetero)aryl bromides^a

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  Table 3.  Direct arylation of azoles with (hetero)aryl bromides^a

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