Aerobic Oxidation of 2-Phenoxyethanol Lignin Model. Compounds Using Vanadium and Copper Catalysts

Transcription

1 Electronic Supporting Information for: Aerobic Oxidation of 2-Phenoxyethanol Lignin Model Compounds Using Vanadium and Copper Catalysts Christian Díaz-Urrutia, Baburam Sedai, Kyle C. Leckett, R. Tom Baker,,* and Susan K. Hanson,* Department of Chemistry and Biomolecular Sciences, and Centre for Catalysis Research and Innovation, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5 Canada. Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA *corresponding authors: Total number of pages: 18 Total number figures: 20 TABLE OF CONTENTS Page S3 Contents Experimental Section S7 Figure S1. 1 H NMR (400 MHz, CDCl 3 ) spectrum of 2-phenoxyethyl formate 8. S7 Figure S2. 13 C{ 1 H} NMR (100 MHz, CDCl 3 ) spectrum of 2-phenoxyethyl formate 8. S8 Figure S3. 1 H NMR (400 MHz, CDCl 3 ) spectrum of 2-phenoxy-2-(2,2,6,6- tetramethylpiperidin-1-yloxy)acetaldehyde 10. S8 S9 Figure S4. 13 C{ 1 H} NMR (100 MHz, CDCl 3 ) spectrum of 2-phenoxy-2-(2,2,6,6- tetramethylpiperidin-1-yloxy)acetaldehyde 10. Figure S5. 1 H NMR (400 MHz, CDCl 3 ) spectrum of 2-phenoxy-1-phenyl-2-(2,2,6,6- tetramethylpiperidin-1-yloxy)ethanone 14. S1

2 S9 Figure S6. 13 C{ 1 H} NMR (100 MHz, CDCl 3 ) spectrum of 2-phenoxy-1-phenyl-2- (2,2,6,6-tetramethylpiperidin-1-yloxy)ethanone 14. S10 Figure S7. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 18 h at 100 C. S10 Figure S8. 13 C{ 1 H} NMR (100 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 18 h at 100 C. S11 Figure S9. COSY NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 18 h at 100 C. S12 Figure S10. HMQC NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 18 h at 100 C. S13 Figure S11. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 40 h at 100 C. S13 Figure S12. 1 H NMR (400 MHz, CDCl 3 ) expanded spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 40 h at 100 C. Compound 11 is highlighted by assigned peaks. S14 Figure S13. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the catalytic oxidation of 2 with oxygen using 5* (20 mol %) after 40 h at 100 C. S14 S15 Figure S14. 1 H NMR spectrum of the reaction mixture (CDCl 3 solution) from the catalytic oxidation of 3 with oxygen using 5* (20 mol %) after 40 h at 100 C. (400 MHz) Figure S15. 1 H NMR (400 MHz, CDCl 3 ) expanded spectrum of the reaction mixture (CDCl 3 solution) from the catalytic oxidation of 3 with oxygen using 5* (20 mol %) after 40 h at 100 C. Compound 13 is highlighted by assigned peaks. S15 Figure S16. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (DMSO-d 6 solution) from the thermolysis of 2-phenoxyacetaldehyde 9 under air after 48 h at 100 C. S16 Figure S17. HPL chromatogram of products from CuCl/TEMPO-mediated oxidation of 2 (40 h at 100 C in toluene) UV-vis detection at nm. S16 Figure S18. GC-MS chromatogram of products from CuCl/TEMPO-mediated oxidation of 2 (40 h at 100 C in toluene). S2

3 S17 Figure S19. HPL chromatogram of products from CuCl/TEMPO-mediated oxidation of 3 (48 h at 100 C in toluene) UV-vis detection at nm S17 Figure S20. GC-MS chromatogram of products from CuCl/TEMPO-mediated oxidation of 3 (48 h at 100 C in toluene). S3

4 EXPERIMENTAL SECTION Catalytic oxidation of formic acid using CuCl/TEMPO (20 mol %) with 2,6-lutidine (10 equiv). In an NMR tube, formic acid (200 μl, 5.30 mmol) was dissolved in CDCl 3 (1 ml) containing dimethylsulfone (8 mg, 0.09 mmol) as an internal standard. An initial 1 H NMR spectrum was recorded, and then the mixture was transferred to a thick-walled 50 ml Schlenk tube equipped with Teflon stopcock containing CuCl (100 mg, 1.01 mmol), TEMPO (0.162 mg, 1.02 mmol), and 10 equivalents (relative to the substrate) of 2,6-lutidine (1.81 ml, 15.5 mmol) dissolved in toluene (6 ml) under air. Oxygen was bubbled into the reaction mixture for 3 minutes and then the reactor was sealed. The reaction mixture was heated at 100 C with constant stirring. After 18 h, examination of the 1 H NMR spectrum revealed complete consumption of the starting material, presumably due to oxidation to CO 2 and H 2 O. No other products were detected by 1 H NMR spectroscopy and GC/MS. Catalytic Oxidation of 1-phenyl-2-phenoxyethanol 3 Using catalyst 6a. In a 25 ml Schlenk flask, 2-phenyl-1-phenoxyethanol (20 mg, mmol) and 1 mol % 6a (0.36 mg, 9.3x10-4 mmol) were dissolved in 1 ml of toluene. The reaction was heated to 105 o C, with constant stirring for 18 h. The reaction mixture changed color to dark-red (a control experiment with only catalyst in toluene does not change color). At the end of the reaction the Schlenk flask was cooled down to room temperature and the solvent was removed under vacuum and replaced by 0.8 ml of CDCl 3 containing 1,3,5-trimethylbenzene (6.0 ul, mmol) as an internal standard. The reaction mixture was transferred to a NMR tube and a 1 H NMR was recorded. Integration against the internal standard revealed 97% conversion of the starting material had occurred, affording 2-phenoxyacetophenone (3%), acetophenone (30%), phenol (40%). Catalytic oxidation of 1-phenyl-2-phenoxyethanol 3 using catalyst 7. In an NMR tube, 1- phenyl-2-phenoxyethanol (41 mg, 0.19 mmol) and the internal standard hexamethylbenzene (6.8 mg, mmol) were dissolved in pyr-d 5 (0.8 ml). Initial NMR spectra were recorded, and then the solution was transferred to a 25 ml round bottom flask containing 7 (8 mg, 0.02 mmol). The reaction was heated under air with stirring at 100 o C for 48 h, using an air condenser. The reaction mixture was cooled to room temperature and the solution was transferred to an NMR tube. 1 H and inverse-gated 13 C NMR spectra were recorded. Integration of the NMR spectra S4

5 against the internal standard revealed that 58% conversion occurred, affording benzoic acid (46%), phenol (45%), 2-phenoxyacetophenone (16%), and formic acid (2%). Catalytic oxidation of 2-phenoxyacetophenone 12 using catalyst 7. In an NMR tube, 2- phenoxyacetophenone (22 mg, 0.10 mmol) was dissolved in pyr-d 5 (0.9 ml) containing dimethylsulfone added as an internal standard. An initial 1 H NMR spectrum was recorded, and then the reaction mixture was transferred to a 50 ml round bottom flask containing 7 (4.0 mg, 0.01 mmol). The flask was equipped with a stir bar and an air condenser, and then the reaction mixture was heated at 100 o C under air with stirring for 48 h. The reaction mixture was cooled to room temperature, and the solution was transferred to an NMR tube. Integration of the 1 H and inverse-gated 13 C NMR spectra revealed that 70% of the starting material was consumed, affording benzoic acid (60%), phenol (70%), and formic acid (2%). Catalytic oxidation of 2-phenoxyacetophenone 12 using catalyst 7 in DMSO-d 6. In an NMR tube, 2-phenoxyacetophenone (20.0 mg, mmol) and 7 (3.9 mg, 0.94 μmol) were dissolved in DMSO-d 6 (1 ml) containing dimethylsulfone (5 mm) as an internal standard. An initial 1 H NMR spectrum was recorded, and then the sample was transferred to a thick-walled 50 ml Schlenk tube equipped with Teflon stopcock. The mixture was heated at 100 o C with constant stirring. The reaction was monitored periodically by NMR over the course of 7 days. At the end of the reaction, integration of the 1 H NMR spectra against the internal standard revealed that 75% conversion of starting material had occurred, affording benzoic acid (51%), phenol (46%), and formic acid (37%). Catalytic oxidation 2-phenoxyacetophenone 12 using catalyst 6a. In a 25 ml Schlenk tube 2- phenoxyacetophenone (20 mg, mmol) and 1 mol % 6a (0.36 mg, 9.3x10-4 mmol) were dissolved in 1 ml of toluene. The reaction was heated to 105 o C with constant stirring for 18 h. At the end of the reaction, the solution turned light green. The Schlenk flask was then cooled to room temperature and the solvent was removed under vacuum. 0.8 ml of CDCl 3 was added to the residue together with 1,3,5-trimethylbenzene (6.0 ul, mmol) as an internal standard. The reaction mixture was transferred to a NMR tube and a 1 H NMR spectrum was recorded. Integration against the internal standard revealed 98% conversion of the starting material had occurred, affording benzaldehyde (5%), benzoic acid (72%), formic acid (9%) and several unidentified aldehyde and formate peaks (ca. 6%). S5

6 Catalytic oxidation of 2-phenoxyethanol 2 using CuCl/TEMPO (20 mol %) with 2,6- lutidine (10 equiv). In an NMR tube, lignin model 2 (25 mg, 0.18 mmol) was dissolved in CDCl 3 (1 ml) containing dimethylsulfone (4.2 mg, mmol) as an internal standard. An initial 1 H NMR spectrum was recorded, and then the sample was transferred to a thick-walled 50 ml Schlenk tube equipped with Teflon stopcock. The solvent was removed by vacuum, and a solution of CuCl (3.0 mg, mmol), TEMPO (6.0 mg, mmol), and 10 equivalents (relative to the substrate) of 2,6-lutidine (207 μl, 1.78 mmol) in toluene (6 ml) was added under air. Oxygen was bubbled into the orange-red reaction mixture for 3 minutes and the reactor sealed. The reaction mixture was heated at 100 C with constant stirring. After 18 h, oxygen was again bubbled into the red reaction mixture for 3 minutes and the reactor sealed. After 40 h, an aliquot of the reaction mixture was taken, the solvent removed, and the residue examined by 1 H NMR (CDCl 3 ). Integration of the NMR spectra against the internal standard revealed approximately 40% conversion of starting material, affording 2-phenoxyethyl-1-formate 8 (12%), 2-phenoxyacetaldehyde 9 (1%), 2-phenoxy-2-(2,2,6,6-tetramethylpiperidin-1- yloxy)acetaldehyde 10 (3%), 11 (9%), and phenol. The phenol could not be quantified from the 1 H NMR spectrum (overlapping aromatic resonances) nor from the GC-MS analysis, as several of the other products undergo decomposition to form phenol during ionization. Control reaction of 2-phenoxyethanol 2 using 2,6-lutidine in toluene (no catalyst). In an NMR tube, 2-phenoxyethanol (20 mg, 0.15 mmol) was dissolved in CDCl 3 (1 ml) containing dimethylsulfone (1.9 mg, mmol) as an internal standard. An initial 1 H NMR spectrum was recorded and the solvent was removed under vacuum. The mixture was then transferred to a thick-walled 50 ml Schlenk tube equipped with Teflon stopcock containing 10 equivalents (relative to the substrate) of 2,6-lutidine (160 μl, 1.37 mmol) dissolved in toluene (5 ml) under air. Oxygen was bubbled into the reaction mixture for 3 minutes and the reactor was sealed. The reaction mixture was heated at 105 C with constant stirring. After 40 h, no reaction was detected by 1 H NMR spectroscopy (integration against the internal standard). Control reaction of the Oxidation of 1-phenyl-2-phenoxyethanol 3 in 2,6-lutidine/toluene (no catalyst). In an NMR tube, substrate 3 (10.0 mg, mmol) was dissolved in CDCl 3 (1 ml) containing dimethylsulfone (1.5 mg, mmol) added as an internal standard. An initial 1 H NMR spectrum was recorded and the solvent was removed under vacuum. The mixture was transferred to a thick-walled 50 ml Schlenk tube equipped with Teflon stopcock containing 10 S6

7 equivalents (relative to the substrate) of 2,6-lutidine (53 μl, 0.46 mmol) dissolved in toluene (5 ml) under air. Oxygen was bubbled into the reaction mixture for 3 minutes and the reactor was sealed. The reaction mixture was heated at 100 C with constant stirring. After 40 h, examination of the 1 H NMR spectrum revealed that no reaction had occurred. S7

8 Figure S1. 1 H NMR (400 MHz, CDCl 3 ) spectrum of 2-phenoxyethyl formate 8. Figure S2. 13 C{ 1 H} NMR (100 MHz, CDCl 3 ) spectrum of 2-phenoxyethyl formate 8. S8

9 ppm Figure S3. 1 H NMR (400 MHz, CDCl 3 ) spectrum of 2-phenoxy-2-(2,2,6,6-tetramethylpiperidin-1- yloxy)acetaldehyde ppm Figure S4. 13 C{ 1 H} NMR spectrum of 2-phenoxy-2-(2,2,6,6-tetramethylpiperidin-1-yloxy)acetaldehyde 10. (100 MHz, CDCl 3 ) S9

10 ppm Figure S5. 1 H NMR (400 MHz, CDCl 3 ) spectrum of 2-phenoxy-1-phenyl-2-(2,2,6,6- tetramethylpiperidin-1-yloxy)ethanone ppm Figure S6. 13 C{ 1 H} NMR (100 MHz, CDCl 3 ) spectrum of 2-phenoxy-1-phenyl-2-(2,2,6,6- tetramethylpiperidin-1-yloxy)ethanone 14. S10

11 ppm Figure S7. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 18 h at 100 C ppm Figure S8. 13 C{ 1 H} NMR (100 MHz, CDCl 3 ) spectrum reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 18 h at 100 C. S11

12 ppm ppm 9 Figure S9. COSY NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 18 h at 100 C. S12

13 ppm ppm Figure S10. HMQC NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 18 h at 100 C. S13

14 ppm Figure S11. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 40 h at 100 C ppm Figure S12. 1 H NMR (400 MHz, CDCl 3 ) expanded spectrum of the reaction mixture (CDCl 3 solution) from the stoichiometric oxidation of 2 with oxygen using 5* after 40 h at 100 C. S14

15 ppm Figure S13. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the catalytic oxidation of 2 with oxygen using 5* (20 mol %) after 40 h at 100 C ppm Figure S14. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (CDCl 3 solution) from the catalytic oxidation of 3 with oxygen using 5* (20 mol %) after 40 h at 100 C. S15

16 ppm Figure S15. 1 H NMR (400 MHz, CDCl 3 ) expanded spectrum of the reaction mixture (CDCl 3 solution) from the catalytic oxidation of 3 with oxygen using 5* (20 mol %) after 40 h at 100 C ppm Figure S16. 1 H NMR (400 MHz, CDCl 3 ) spectrum of the reaction mixture (DMSO-d 6 solution) from the thermolysis of 2-phenoxyacetaldehyde under air after 48 h at 100 C. S16

17 2 2,6-lutidine TEMPO Figure S17. HPL chromatogram of products from CuCl/TEMPO-mediated oxidation of 2 (40 h at 100 C in toluene) UV-vis detection 251.8nm. phenol TEMPO *benzaldehyde 2 8 2,6-lutidine Figure S18. GC-MS chromatogram of products from CuCl/TEMPO-mediated oxidation of 2 (40 h at 100 C in toluene). * Benzaldehyde is derived from oxidation of toluene solvent. S17

18 14 3 Benzoic acid + 2,6- lutidine Figure S19. HPL chromatogram of products from CuCl/TEMPO-mediated oxidation of 3 (40 h at 100 C in toluene) UV-vis detection 251.8nm. 3 *benzaldehyde 13 2,6-lutidine 12 TEMPO Figure S20. GC-MS chromatogram of products from CuCl/TEMPO-mediated oxidation of 2 (40 h at 100 C in toluene). *Benzaldehyde is derived from oxidation of toluene solvent. S18