Copper-Catalyzed Cascade Cycloamination of alpha-csp 3 -H Bond of N-Aryl Ketimines with Azides: Access to Quinoxalines Tengfei Chen, Xun Chen, Jun Wei, Dongen Lin *, Ying Xie, and Wei Zeng * School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641, China Table of Contents Supporting Information 1. General experimental information... 2 1.1. Table 1. Catalyst screening for copper-catalyzed alpha- Csp 3 -H bond cycloamination of N-aryl ketimine 1a a... 3 1.2. Table 2. The effect of the solvent on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a... 3 1.3. Table 3. The effect of the azide on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a... 4 1.4. Table 4. The effect of the oxidant on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a... 4 1.5. Table 5. The effect of the proton source on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a... 5 1.6. General procedure for the synthesis of N-phenylketimines... 5 1.7 General procedure for synthesis of quinoxaline derivatives (2a-2z)... 5 1.8 Synthesis of (Z)-N-(4-methoxyphenyl)benzimidoyl cyanide (3)... 13 2. Control experiments for mechanism studies... 13 3. References... 14 4. 1 H NMR and 13 C NMR spectrum for all isolated products.... 15
1. General experimental information All reactions were carried out in flame-dried sealed tubes with magnetic stirring. Unless otherwise noted, all experiments were performed under argon atmosphere. All reagents were purchased from TCI, Acros or Strem. Solvents were treated with 4 Å molecular sieves or sodium and distilled prior to use. Purifications of reaction products were carried out by flash chromatography using Qingdao Haiyang Chemical Co. Ltd silica gel (40-63 mm). 1 H NMR and 13 C NMR spectra were recorded with tetramethylsilane (TMS) as internal standard at ambient temperature unless otherwise indicated on a Bruker Avance DPX 600 fourier Transform spectrometer operating at 400 MHz for 1 H NMR and 100 MHz for 13 C NMR. Chemical shifts are reported in parts per million (ppm) and coupling constants are reported as Hertz (Hz). Splitting patterns are designated as singlet (s), broad singlet (bs), doublet (d), triplet (t). Splitting patterns that could not be interpreted or easily visualized are designated as multiple (m). Low resolution mass spectra were recorded using a Waters HPLC/ZQ4000 Mass Spectrometer.Gas chromatograph mass spectra were obtained with a SHIMADZU model GCMS-QP5000 spectrometer. 2
1.1. Table 1. Catalyst screening for copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a Entry Catalyst Yield (%) b 1 CuO 19 2 CuBr trace 3 CuBr 2 trace 4 CuI 5 5 CuCl 2 5 6 CuCl 0 7 Cu(OAC) 2 9 8 CuSO 4 14 9 Cu(OTf) 2 0 10 Cu(TFA) 2 0 11 Cu 2 (BF 4 )H 2 O 0 a The reactions were carried out using N-aryl ketimine 1a (0.1 mmol), NaN 3 (0.3 mmol) with Cu catalyst (10 mol%) in the presence of PIDA (0.3 mmol) and AcOH (0.2 mmol) in solvent (2.0 ml) at 25 o C for 16 h in a sealed reaction tube under Ar, followed by flash chromatography on SiO 2. b Isolated yield. 1.2. Table 2. The effect of the solvent on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a Entry Solvent Yield (%) b 1 CH 2 Cl 2 5 2 ClCH 2 CH 2 Cl 9 3 CH 3 CH 2 OH 0 4 1,4-dioxane 14 5 EtOAc 19 6 CHCl 3 5 7 toluene 14 8 THF 9 9 CH 3 CN 5 10 CH 3 OCH 3 9 a The reactions were carried out using N-aryl ketimine 1a (0.1 mmol), NaN 3 (0.3 mmol) with CuO 3
(10 mol%) in the presence of PIDA (0.3 mmol) and AcOH (0.2 mmol) in given solvent (2.0 ml) at 25 o C for 16 h in a sealed reaction tube under Ar, followed by flash chromatography on SiO 2. b Isolated yield. 1.3. Table 3. The effect of the azide on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a Entry Azide Yield (%) b 1 NaN 3 49 2 TsN 3 19 3 PhCON 3 0 4 TMSN 3 39 5 PhN 3 0 a The reactions were carried out using N-aryl ketimine 1a (0.1 mmol), azide (0.3 mmol) with CuO (10 mol%) in the presence of PIDA (0.3 mmol) and AcOH (0.2 mmol) in EtOAc (2.0 ml) at 25 o C for 16 h in a sealed reaction tube under Ar, followed by flash chromatography on SiO 2. b Isolated yield 1.4. Table 4. The effect of the oxidant on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a Entry Oxidant Yield (%) b 1 benzoquinnone 0 2 PhIO 0 3 MnO 2 0 4 NaS 2 O 8 0 5 AgOAc 19 6 Ag 2 CO 3 0 7 PhI(OAc) 2 49 8 PhI(OOCF 3 ) 2 0 a The reactions were carried out using N-aryl ketimine 1a (0.1 mmol), NaN 3 (0.3 mmol) with CuO (10 mol%) in the presence of oxidant (0.3 mmol) and AcOH (0.2 mmol) in EtOAc (2.0 ml) at 25 o C for 16 h in a sealed reaction tube under Ar, followed by flash chromatography on SiO 2. b Isolated yield. 4
1.5. Table 5. The effect of the proton source on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1a a Entry Acid Yield (%) b 1 CH 3 COOH 49 2 CF 3 SO 3 H 0 3 PhCOOH 29 4 PivOH 71 5 TsOH 0 6 iproh 0 a The reactions were carried out using N-aryl ketimine 1a (0.1 mmol), NaN 3 (0.3 mmol) with CuO (10 mol%) in the presence of PIDA (0.3 mmol) and acid (0.2 mmol) in EtOAc (2.0 ml) at 25 o C for 16 h in a sealed reaction tube under Ar, followed by flash chromatography on SiO 2. b Isolated yield. 1.6 General procedure for the synthesis of N-aryl ketimines 3 R R 1 + NH 2 O R 1 10 mol % H 2 SO 4 N toluene, reflux R 3 R 2 R 2 The mixture of acetophenone derivatives (0.2 mmol, 1.0 equiv.) and substituted anilines (0.2 mmol, 1.0 equiv.) was stirred in toluene (3.0 ml) at 120 o C for 24 h in the presence of molecular sieve (4 Å) (0.40 g) and a catalytic amount of concentrated H 2 SO 4 (10 mol%). The mixture was then filtered and the solvent was removed under reduced pressure to produce the corresponding crude N-aryl ketimines. These crude N-aryl ketimines could be directly used for synthetic purpose without further purification because these N-aryl ketimines are easily decomposed on silica gel. [1] 1.7 General procedure for synthesis of quinoxaline derivatives (2a-2z) To the solution of N-aryl ketimines 1 (0.1 mmol) in dry EtOAc (2.0 ml) were added CuO (0.8 mg, 10 mol%), NaN 3 (19.5 mg, 0.3 mmol), PIDA (96.6 mg, 0.3 mmol) and PivOH ( 20.4 mg, 0.2 mmol) under Ar atmosphere, and then the corresponding reaction mixture was stirred in a sealed tube at 25 o C for 16 h. After the starting materials were disappeared, then the mixture was filtered, and the corresponding organic layers were concentrated under vacuum, and the resulting crude product was purified by flash column chromatography using 10 20% (v/v) ethyl acetate in petroleum ether as eluent to afford the desired phenylquinoxaline 2 as a white solid. 5
2a 2-Phenylquinoxaline (2a) [2] : White solid; 15 mg, 71% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.30 (s, 1H), 8.13 (ddd, J = 14.0, 11.8, 4.2 Hz, 4H), 7.78 7.66 (m, 2H), 7.58 7.44 (m, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 151.8, 143.3, 142.3, 141.6, 136.7, 130.2, 130.2, 129.6, 129.5, 129.1, 127.5. MS (ESI): m/z = 206.21 [M] +. 2b 2-(p-Tolyl)quinoxaline (2b) [2] : White solid; 17 mg, 77% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.29 (s, 1H), 8.10 (dd, J = 15.9, 8.2 Hz, 4H), 7.72 (ddd, J = 15.2, 13.8, 6.8 Hz, 2H), 7.34 (d, J = 8.0 Hz, 2H), 2.43 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 151.0, 143.2, 141.6, 140.7, 140.1, 136.9, 132.6, 129.9, 129.1, 129.1, 127.9, 127.4, 21.8. MS (ESI): m/z = 220.12 [M] +. 2c 2-(4-Methoxyphenyl)quinoxaline (2c) [2] : White solid; 19 mg, 80% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.29 (s, 1H), 8.17 (d, J = 8.1 Hz, 2H), 8.10 (t, J = 9.0 Hz, 2H), 7.73 (dt, J = 14.5, 7.0 Hz, 2H), 7.08 (d, J = 8.1 Hz, 2H), 3.90 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 161.5, 151.5, 143.1, 142.3, 141.2, 130.1, 129.4, 129.3, 129.0, 128.9, 114.6, 99.9, 55.4. MS (ESI): m/z = 236.20 [M] +. 2d 2-(4-Fluorophenyl)quinoxaline (2d) [3] : White solid; 16 mg, 68% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.29 (s, 1H), 8.20 (dd, J = 8.7, 5.4 Hz, 2H), 8.13 (dd, J = 11.0, 4.0 Hz, 2H), 7.82 7.70 (m, 2H), 7.25 (dd, J = 10.5, 6.7 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 164.3 (d, J = 251.5 Hz), 150.7, 142.9, 142.2, 141.5, 132.9 (d, J = 1.0 Hz), 130.4, 129.5, 129.5, 129.4, 129.1, 116.2 (d, J = 22.2 Hz). MS (ESI): m/z = 224.19 [M] +. 6
2e 2-(4-Chlorophenyl)quinoxaline (2e) [2] : Yellow solid; 16 mg, 68% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.31 (s, 1H), 8.17 (d, J = 7.4 Hz, 4H), 7.79 (t, J = 7.7 Hz, 2H), 7.55 (d, J = 7.8 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 150.6, 142.8, 142.2, 141.6, 136.6, 135.1, 130.5, 129.7, 129.6, 129.3, 129.1, 128.7. MS (ESI): m/z = 240.18 [M] +. 2f 2-(4-Bromophenyl)quinoxaline (2f) [2] : Yellow solid; 17 mg, 60% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.26 (s, 1H), 8.10 (t, J = 6.7 Hz, 2H), 8.05 (d, J = 8.3 Hz, 2H), 7.81 7.70 (m, 2H), 7.66 (d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 150.5, 142.7, 142.1, 141.6, 135.5, 132.3, 130.4, 129.8, 129.6, 129.1, 128.9, 124.9. MS (ESI): m/z = 284.10 [M] +. 2g 4-(Quinoxalin-2-yl)benzonitrile (2g) [3] : Yellow solid; 12 mg, 52% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.28 (s, 1H), 8.27 (d, J = 8.1 Hz, 2H), 8.09 (t, J = 6.1 Hz, 2H), 7.83 7.69 (m, 4H); 13 C NMR (100 MHz, CDCl 3 ) δ 148.55, 141.73, 141.19, 141.03, 139.81, 131.85, 129.81, 129.53, 128.78, 128.23, 127.01, 117.45, 112.67. MS (ESI): m/z = 231.22 [M] +. 2h 2-(4-Nitrophenyl)quinoxaline (2h) [3] : Yellow solid; 14 mg, 56% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.39 (s, 1H), 8.46 8.38 (m, 4H), 8.23 8.15 (m, 2H), 7.89 7.79 (m, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 149.26, 148.88, 142.81, 142.59, 142.24, 142.15, 130.89, 130.69, 129.87, 129.30, 128.36, 124.31. MS (ESI): m/z = 251.10 [M] +. 7
2i Methyl 4-(quinoxalin-2-yl)benzoate (2i) [4] : White solid; 15 mg, 57% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.27 (s, 1H), 8.11 (ddd, J = 20.0, 17.9, 8.3 Hz, 6H), 7.70 (t, J = 6.6 Hz, 2H), 3.89 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 166.6, 150.5, 143.1, 142.2, 141.8, 140.7, 131.4, 130.5, 130.3, 130.0, 129.75, 129.2, 127.5, 52.3. MS (ESI): m/z = 264.22 [M] +. 2j 2-(3-Methoxyphenyl)quinoxaline (2j) [3] : White solid; 16 mg, 65% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.29 (s, 1H), 8.12 (dd, J = 15.0, 8.1 Hz, 2H), 7.79 7.70 (m, 4H), 7.44 (t, J = 8.0 Hz, 1H), 7.04 (dd, J = 8.2, 2.0 Hz, 1H), 3.91 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 160.3, 151.5, 143.4, 142.2, 141.6, 138.1, 130.2, 130.1, 129.6, 129.5, 129.1, 119.9, 116.2, 112.7, 55.4. MS (ESI): m/z = 236.22 [M] +. 2k 2-(3-Chlorophenyl)quinoxaline (2k) [2] : White solid; 17 mg, 66% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.30 (s, 1H), 8.23 (s, 1H), 8.15 (t, J = 9.0 Hz, 2H), 8.06 (s, 1H), 7.84 7.73 (m, 2H), 7.50 (d, J = 3.7 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 150.3, 142.9, 142.2, 141.8, 138.5, 135.3, 130.5, 130.3, 130.2, 129.9, 129.6, 129.1, 127.6, 125.5. MS (ESI): m/z = 240.18 [M] +. 2l 2-(2-Methoxyphenyl)quinoxaline (2l) [2] : Red solid; 13 mg, 55% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.34 (s, 1H), 8.18 8.08 (m, 2H), 7.90 (dd, J = 7.6, 1.6 Hz, 1H), 7.75 7.66 (m, 2H), 7.48 7.41 (m, 1H), 7.14 (t, J = 7.4 Hz, 1H), 7.02 (d, J = 8.3 Hz, 1H), 3.86 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 157.39, 152.19, 147.27, 142.69, 141.05, 131.61, 131.43, 129.73, 129.53, 129.34, 129.06, 126.51, 8
121.51, 111.44, 55.62. MS (ESI): m/z = 236.22 [M] +. 2m 2-(2-Chlorophenyl)quinoxaline (2m) [2] : Yellow solid; 12 mg, 50% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.21 (s, 1H), 8.19 8.13 (m, 2H), 7.78 (dd, J = 6.4, 3.4 Hz, 2H), 7.75 7.69 (m, 1H), 7.55 7.49 (m, 1H), 7.46 7.38 (m, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 152.3, 146.1, 142.2, 141.3, 136.5, 132.5, 131.9, 130.8, 130.2, 130.2, 130.1, 129.6, 129.2, 127.4. MS (ESI): m/z = 240.18 [M] +. 2n 2-(Quinoxalin-2-yl)phenol (2n) [5] : White solid; 10 mg, 45% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 13.73 (s, 1H), 9.51 (s, 1H), 8.09 (ddd, J = 14.6, 7.9, 1.1 Hz, 2H), 8.01 (dd, J = 8.1, 1.1 Hz, 1H), 7.82 7.71 (m, 2H), 7.45 7.37 (m, 1H), 7.11 (dd, J = 8.3, 0.7 Hz, 1H), 7.06 6.97 (m, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ 160.9, 151.8, 142.6, 140.8, 138.3, 132.9, 131.0, 129.6, 129.3, 127.5, 126.7, 119.4, 118.8, 117.2. MS (ESI): m/z = 221.18 [M] +. 2o 6-Methoxy-2-phenylquinoxaline (2o) [2] : White solid; 20 mg, 85% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.25 (s, 1H), 8.16 (d, J = 8.0 Hz, 2H), 8.04 (d, J = 9.1 Hz, 1H), 7.56 (t, J = 7.6 Hz, 2H), 7.52 7.47 (m, 1H), 7.46 7.40 (m, 2H), 3.99 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 160.5, 149.6, 143.1, 143.0, 138.4, 136.9, 130.5, 129.7, 129.0, 127.1, 123.5, 106.5, 55.8. MS (ESI): m/z = 236.22 [M] +. 2p 6-Methyl-2-phenylquinoxaline (2p) [2] : White solid; 18 mg, 82% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.26 (s, 1H), 8.16 (d, J = 7.4 Hz, 2H), 8.03 (d, J = 8.5 Hz, 1H), 7.87 (s, 1H), 7.62 7.47 (m, 4H), 2.59 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 151.0, 143.2, 141.6, 140.7, 140.1, 136.9, 132.5, 129.9, 129.1, 129.1, 127.9, 127.4, 21.8. MS (ESI): m/z = 220.20 [M] +. 9
2q 6-Fluoro-2-phenylquinoxaline (2q) [3] : White solid; 9 mg, 40% yield ; 1 H NMR (400 MHz, CDCl 3 ) δ 9.22 (s, 1H), 8.12 8.00 (m, 3H), 7.65 (dd, J = 9.0, 2.5 Hz, 1H), 7.52 7.40 (m, 4H); 13 C NMR (100 MHz, CDCl 3 ) δ 162.5 (d, J = 253.5 Hz), 151.3, 144.0, 142.3 (d, J = 13.1 Hz), 139.5, 136.5, 131.7 (d, J = 10.1 Hz), 130.2, 129.2, 127.4, 120.7 (d, J = 26.3 Hz), 112.7 (d, J = 22.2 Hz). MS (ESI): m/z = 224.13 [M] +. 2r 6-Bromo-2-phenylquinoxaline (2r) [2] : White solid; 8 mg, 33% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.25 (s, 1H), 8.11 (d, J = 7.5 Hz, 2H), 8.06 7.97 (m, 2H), 7.65 (d, J = 9.0 Hz, 1H), 7.48 (p, J = 6.6 Hz, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 151.9, 144.1, 141.8, 140.8, 136.4, 135.3, 131.3, 130.9, 130.4, 129.2, 128.1, 127.5. MS (ESI): m/z = 240.09 [M] +. 2s 6-Chloro-2-phenylquinoxaline (2s) [2] : White solid; 10 mg, 35% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.23 (s, 1H), 8.21 (s, 1H), 8.10 (d, J = 7.5 Hz, 2H), 7.93 (d, J = 8.9 Hz, 1H), 7.77 (d, J = 8.9 Hz, 1H), 7.53 7.43 (m, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 152.0, 144.1, 142.1, 141.1, 136.4, 133.8, 131.5, 130.9, 130.5, 129.2, 127.5, 123.4. MS (ESI): m/z = 283.30 [M] +. 2t 8-Methoxy-2-phenylquinoxaline (2t) [2] : White solid; 17 mg, 72% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.33 (s, 1H), 8.20 (d, J = 7.7 Hz, 2H), 7.77 7.62 (m, 2H), 7.60 7.49 (m, 3H), 7.13 (d, J = 7.6 Hz, 1H), 4.12 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 155.4, 150.7, 143.6, 142.4, 136.8, 134.5, 130.0, 129.6, 129.1, 127.7, 120.9, 108.6, 56.4. MS (ESI): m/z = 236.11 [M] +. 10
2u 2-(Pyridin-4-yl)quinoxaline (2u) [6] : Yellow solid; 12 mg, 57% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.33 (s, 1H), 8.82 (d, J = 3.8 Hz, 2H), 8.14 (d, J = 6.7 Hz, 2H), 8.07 (d, J = 4.0 Hz, 2H), 7.86 7.75 (m, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 150.7, 149.0, 143.8, 142.6, 142.3, 142.2, 130.7, 130.6, 129.8, 129.2, 121.3. MS (ESI): m/z = 207.22 [M] +. 2v 2-(Pyridin-2-yl)quinoxaline (2v) [6] : Yellow solid; 11 mg, 53% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.93 (s, 1H), 8.72 (d, J = 4.4 Hz, 1H), 8.51 (d, J = 7.9 Hz, 1H), 8.10 (ddd, J = 9.9, 5.3, 1.9 Hz, 2H), 7.80 (td, J = 7.8, 1.4 Hz, 1H), 7.71 (d, J = 4.9 Hz, 2H), 7.32 (dd, J = 7.0, 5.1 Hz, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ 154.4, 150.0, 149.3, 144.0, 142.4, 141.6, 136.9, 130.0, 129.9, 129.6, 129.2, 124.5, 121.9. MS (ESI): m/z = 207.21 [M] +. 2w 2-(Furan-2-yl)quinoxaline (2w) [3] : Yellow solid; 10 mg, 51% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.25 (s, 1H), 8.14 8.03 (m, 2H), 7.79 7.64 (m, 3H), 7.32 (s, 1H), 6.63 (s, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ 151.6, 145.1, 143.9, 142.1, 141.3, 130.5, 129.3, 129.2, 112.5, 111.8. MS (ESI): m/z = 196.18 [M] +. 2x 2-(Thiophen-2-yl)quinoxaline (2x) [3] : White solid; 10 mg, 47% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 9.24 (s, 1H), 8.06 (dd, J = 8.2, 2.4 Hz, 2H), 7.86 (d, J = 3.6 Hz, 1H), 7.78 7.68 (m, 2H), 7.55 (d, J = 5.0 Hz, 1H), 7.23 7.18 (m, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ 147.4, 142.3, 142.2, 142.1, 141.4, 130.4, 129.8, 129.2, 129.1, 128.5, 127.0. MS (ESI): m/z = 212.14 [M] +. 11
2y 2-Chloro-3-phenylquinoxaline (2y) [7] : White solid; 8 mg, 33% yield; 1 H NMR (400 MHz, DMSO) δ 8.20 8.13 (m, 1H), 8.13 8.05 (m, 1H), 7.97 7.89 (m, 2H), 7.84 (d, J = 2.9 Hz, 2H), 7.57 (d, J = 2.7 Hz, 3H); 13 C NMR (100 MHz, DMSO) δ 152.49, 145.51, 140.29, 140.25, 136.43, 131.27, 130.88, 129.62, 129.55, 128.80, 128.07, 127.69. MS (ESI): m/z = 240.08 [M] +. 2z 2-Methyl-3-phenylquinoxaline (2z) [8] : White solid; 14 mg, 62% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 8.12 (d, J = 7.7 Hz, 1H), 8.06 (d, J = 7.7 Hz, 1H), 7.77 7.69 (m, 2H), 7.66 (d, J = 7.1 Hz, 2H), 7.56 7.47 (m, 3H), 2.78 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 154.9, 152.6, 141.3, 141.0, 139.1, 129.7, 129.2, 129.0, 128.9, 128.6, 128.3, 29.7. MS (ESI): m/z = 220.18 [M] +. 2-1z 2,3-Diphenylquinoxaline (2-1z) [8] : White solid; 9 mg, 31% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 8.18 (dd, J = 6.0, 3.4 Hz, 2H), 7.76 (dd, J = 6.1, 3.3 Hz, 2H), 7.52 (d, J = 6.4 Hz, 4H), 7.34 (d, J = 6.9 Hz, 6H); 13 C NMR (100 MHz, CDCl 3) δ 153.5, 141.3, 139.1, 130.0, 129.9, 129.2, 128.8, 128.3. MS (ESI): m/z = 282.28 [M] +. 2-2z 2-Benzyl-3-phenylquinoxaline (2-2z) [8] : White solid; 19 mg, 80% yield; 1H NMR (400 MHz, CDCl3) δ 8.16 8.07 (m, 2H), 7.77 7.68 (m, 2H), 7.43 (s, 5H), 7.18 7.08 (m, 3H), 6.98 (d, J = 7.1 Hz, 2H), 4.40 (s, 2H); 13C NMR (100 MHz, CDCl3) δ 141.4, 141.0, 139.0, 138.2, 129.8, 129.6, 129.2, 129.0, 128.9, 128.9, 128.5, 128.3, 126.4, 42.3. MS (ESI): m/z = 296.22 [M] +. 12
1.8 Synthesis of (Z)-N-(4-methoxyphenyl)benzimidoyl cyanide (3) The mixture of (E)-4-methoxy-N-(1-phenylethylidene)aniline (1a) (0.2 mmol, 45.0 mg), azidotrimethylsilane (0.4 mmol, 48.0 mg), sodium bromide (0.4 mmol, 41.0 mg), iodobenzene diacetate (0.6 mmol, 192.0 mg), DMSO (2.0 ml) was stirred at 20 o C under air. After 12 hours, water (5 ml) was added to the mixture and extracted with ethyl acetate (10.0 ml 3). Dried with anhydrous magnesium sulfate and concentrated and purified by flash chromatography on silicon gel to afford 3 as yellow solid. 3 (Z)-N-(4-Methoxyphenyl)benzimidoyl cyanide (3) [9] : Yellow solid; 38 mg, 80% yield; 1 H NMR (400 MHz, CDCl 3 ) δ 8.13 (d, J = 7.5 Hz, 1H), 7.58 7.49 (m, 1H), 7.33 (d, J = 8.9 Hz, 1H), 7.00 (d, J = 8.9 Hz, 1H), 3.86 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 159.5, 141.8, 136.9, 134.1, 132.4, 129.0, 127.9, 123.0, 114.5, 111.7, 55.5. MS (ESI): m/z = 236.08 [M] +. 2. Control experiments for mechanism studies (a) PIDA-promoted alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1o To the solution of N-phenylketoimines 1o (0.1 mmol) in dry EtOAc (2.0 ml) were added NaN 3 (19.5 mg, 0.3 mmol), PIDA (96.6 mg, 0.3 mmol) and PivOH (20.4 mg, 0.2 mmol) under Ar atmosphere, and then the corresponding reaction mixture was stirred in a sealed tube at 25 o C for 16 h. Both desired 2o and 4 were not observed under these conditions. (b) Control experiment for this transformation using cyanide 3 as starting material To the solution of (Z)-N-(4-methoxyphenyl)benzimidoyl cyanide 3 (0.1 mmol) in dry EtOAc (2.0 ml) were added CuO (0.8 mg, 10 mol %) NaN 3 (19.5 mg, 0.3 mmol), PIDA (96.6 mg, 0.3 mmol) and PivOH (20.4 mg, 0.2 mmol) under Ar atmosphere, and then the corresponding reaction 13
mixture was stirred in a sealed tube at 25 o C for 16 h. The desired 2o were not observed under standard conditions, and substrate 3 was recovered in 87% yield. (c): The effect of TEMPO on the copper-catalyzed alpha-csp 3 -H bond cycloamination of N-aryl ketimine 1o To the solution of N-arylketoimines 1o (0.1 mmol) in dry EtOAc (2.0 ml) were added CuO (0.8 mg, 10 mol%),nan 3 (19.5 mg, 0.3 mmol), PIDA (96.6 mg, 0.3 mmol),pivoh (20.4 mg, 0.2 mmol) and TEMPO (31.2 mg,0.2 mmol) under Ar atmosphere, and then the corresponding reaction mixture was stirred in a sealed tube at 25 o C for 16 h. The desired 2o were not observed under these conditions. 3. References 1. Ye, W.; Indubhusan, D.; Naohiko, Y. J. Am. Chem. Soc. 2012, 134, 9098. 2. Nguyen, T. B.; Retailleau, P.; Al-Mourabit. A. Org. Lett. 2013, 15, 5238. 3. Vadagaonkar, K. S.; Kalmode, H, P.; Murugan, K.; Chaskar, A. C. RSC Adv. 2015, 5, 5580. 4. Leclerc, J.; Fagnou, K. Angew. Chem., Int. Ed. 2006, 45, 7781. 5. Madhav, B.; Murthy, S. N.; Reddy, V. P.; Rao, K. R.; Nageswar, Y. V. D. Tetrahedron Lett. 2009, 50, 6025. 6. Jung, D.; Song, J.; Kim, Y.; Lee, D.; Lee,Y.; Park, Y.; Choi, S.; Hahn J. Bull. Korean Chem. Soc. 2007, 28, 1877. 7. Rao, K. R.; Raghunadha, A.; Kalitaa, D.; Laxminarayanab, E.; Palc, M.; Meruva, S. B. Der Pharma Chemica. 2015, 7, 77. 8. Lassagne, F.; Chevalliera,F.; Roisnelb, T.; Dorcetb, V.; Mongin, F.; Domingo, L. R. synthesis 2015, 47, 2680. 9. Chen, F.; Huang, X.; Cui, Y.; Jiao, N. Chem.-Eur. J. 2013, 19, 11199. 14
4. 1 H NMR and 13 C NMR spectrum for all isolated products. 1) The 1 H NMR and 13 C NMR spectrum for 2a (Using CDCl 3 as solvent) 15
2) The 1 H NMR and 13 C NMR spectrum for 2b (Using CDCl 3 as solvent) 16
3) The 1 H NMR and 13 C NMR spectrum for 2c (Using CDCl 3 as solvent) 17
4) The 1 H NMR and 13 C NMR spectrum for 2d (Using CDCl 3 as solvent) 18
5) The 1 H NMR and 13 C NMR spectrum for 2e (Using CDCl 3 as solvent) 19
6) The 1 H NMR and 13 C NMR spectrum for 2f (Using CDCl 3 as solvent) 20
7) The 1 H NMR and 13 C NMR spectrum for 2g (Using CDCl 3 as solvent) 21
8) The 1 H NMR and 13 C NMR spectrum for 2h (Using CDCl 3 as solvent) 22
9) The 1 H NMR and 13 C NMR spectrum for 2i (Using CDCl 3 as solvent) 23
10) The 1 H NMR and 13 C NMR spectrum for 2j (Using CDCl 3 as solvent) 24
11) The 1 H NMR and 13 C NMR spectrum for 2k (Using CDCl 3 as solvent) 25
12) The 1 H NMR and 13 C NMR spectrum for 2l (Using CDCl 3 as solvent) 26
13) The 1 H NMR and 13 C NMR spectrum for 2m (Using CDCl 3 as solvent) 27
14) The 1 H NMR and 13 C NMR spectrum for 2n (Using CDCl 3 as solvent) 28
15) The 1 H NMR and 13 C NMR spectrum for 2o (Using CDCl 3 as solvent) 29
16) The 1 H NMR and 13 C NMR spectrum for 2p (Using CDCl 3 as solvent) 30
17) The 1 H NMR and 13 C NMR spectrum for 2q (Using CDCl 3 as solvent) 31
18) The 1 H NMR and 13 C NMR spectrum for 2r (Using CDCl 3 as solvent) 32
19) The 1 H NMR and 13 C NMR spectrum for 2s (Using CDCl 3 as solvent) 33
20) The 1 H NMR and 13 C NMR spectrum for 2t (Using CDCl 3 as solvent) 34
21) The 1 H NMR and 13 C NMR spectrum for 2u (Using CDCl 3 as solvent) 35
22) The 1 H NMR and 13 C NMR spectrum for 2v (Using CDCl 3 as solvent) 36
23) The 1 H NMR and 13 C NMR spectrum for 2w (Using CDCl 3 as solvent) 37
24) The 1 H NMR and 13 C NMR spectrum for 2x (Using CDCl 3 as solvent) 38
25) The 1 H NMR and 13 C NMR spectrum for 2y (Using DMSO-d6 as solvent) 39
26) The 1 H NMR and 13 C NMR spectrum for 2z (Using CDCl 3 as solvent) 40
27) The 1 H NMR and 13 C NMR spectrum for 2-1z (Using CDCl 3 as solvent) 41
28) The 1 H NMR and 13 C NMR spectrum for 2-2z (Using CDCl 3 as solvent) 42
29) The 1 H NMR and 13 C NMR spectrum for 3 (Using CDCl 3 as solvent) 43
44