Electronic Supplementary Material (ESI) for Green Chemistry. This journal is © The Royal Society of Chemistry 2017 Supporting Information Sustainable Production of Pyromellitic Acid with Pinacol and Diethyl Maleate Yancheng Hu,a Ning Li,*a,b Guangyi Li,a Aiqin Wang,a,b Yu Cong,a Xiaodong Wanga and Tao Zhang*a,b aState Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China. biChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China. *E-mail: [email protected]; [email protected] 1. General information Pinacol was purchased from Aladdin Industrial Inc. Diethyl maleate and ethyl acrylate were obtained from Tokyo Chemical Industry. Choline chloride and formic acid were supplied by Acros Organics. Other carboxylic acids were provided by Aladdin Industrial Inc. All chemicals were of analytical grade and were used without further purification. Various deep eutectic solvents (DESs) were prepared according to literature1 by stirring choline chloride and the other component at 100 oC until a homogeneous liquid was formed (ca. 40 min). Amberlyst-15 resin was purchased from Sigma-Aldrich company. The Raney Ni, Ni/C, Pd/C, Pt/C, Ru/C and Rh/C catalysts were purchased from Aladdin Industrial Inc. To facilitate the comparison, the metal contents in these catalysts were chosen as 5% by weight. NMR spectra were recorded at room temperature in CDCl3 on 400 MHz spectrometers. The chemical shifts for 1H NMR were recorded in ppm downfield 6 using the peak of CDCl3 (7.26 ppm) or d -DMSO (2.50 ppm) as the internal standard. The chemical shifts for 13C NMR were recorded in ppm downfield using the central 6 peak of CDCl3 (77.16 ppm) or d -DMSO (39.52 ppm) as the internal standard. HRMS data was obtained with Micromass HPLC-Q-TOF mass spectrometer (ESI) or Agilent 6540 Accurate-MS spectrometer (Q-TOF). 2. Pinacol dehydration to 2,3-dimethylbutadiene 2.1 Pinacol dehydration using Amberlyst-15 resin as catalyst 1,2-Elimination HO OH -2 H2O Amberlyst-15 2 solvent O Pinacol, 1 Pinacol rearrangement 3 Pinacol (8.5 mmol, 1.0 g), Amberlyst-15 resin (100 mg), and solvent (4.0 g or 0 g for the solvent-free test) were added to a sealed tube (35 mL) in sequence. The S1 mixture was stirred at 120 oC for 12 h. Upon completion, the product was diluted with pentane and analyzed by an Agilent GC 7890A equipped with HP-5 column (30 m, 0.25 mm ID, 0.5 mm film) and a flame ionization detector (FID) using tridecane as the internal standard. Examples see Fig. S1 (no solvent, compound 3 in 88% carbon yield) and Fig. S2 (DMSO as solvent, compound 2 in 31% carbon yield, compound 3 in 15% carbon yield; NMP as solvent, compound 2 in 39% carbon yield, compound 3 in 21% carbon yield). 2.2 Pinacol dehydration in acidic deep eutectic solvents (DESs) 1,2-Elimination HO OH -2 H2O acidic DES 2 O Pinacol, 1 Pinacol rearrangement 3 Pinacol (8.5 mmol, 1.0 g) and acidic DES (4-10 g) were added to a sealed tube (35 mL) in sequence. The reaction mixture was stirred at 100-150 oC for 12 h. Upon completion, the product was diluted with pentane and analyzed by an Agilent GC 7890A equipped with HP-5 column (30 m, 0.25 mm ID, 0.5 mm film) and a FID using tridecane as the internal standard. Example see Fig. S3 (8.0 g ChCl/HCOOH, 140 oC, compound 2 in 83% yield, compound 3 in 13% yield) and Fig. S4 (8.0 g ChCl/HCOOH, 150 oC, compound 2 in 71% yield, compound 3 in 16% yield). The influence of ChCl/HCOOH dosage on the dehydration of pinacol was studied. According to Fig. S5, the carbon yield of compound 2 increased with the increment of ChCl/HCOOH dosage, reached the maximum (78%) when 8.0 g ChCl/HCOOH was used, then stabilized with further increasing the dosage. In contrast, it is noticed that the dosage of DES had no evident effect on the the carbon yield of compound 3. We also investigated the effect of reaction temperature on the carbon yields of compounds 2 and 3. Taking into consideration that the thermal decomposition of formic acid is 160 oC, we set the maximum reaction temperature as 150 oC. As shown in Fig. S6, with the increasing of reaction temperature, the carbon yield of compound 2 slightly increased, reached the maximum (83%) when the pinacol dehydration was S2 performed at 140 oC, then decreased with further increment of the temperature. This can be rationalized because too high temperature led to the self D-A reaction of compound 2 (Fig. S4), which decreased its carbon yield or selectivity. 2.3 Recycling performance of ChCl/HCOOH in pinacol dehydration Pinacol (8.5 mmol, 1.0 g) and ChCl/HCOOH (molar ratio 2:1, 8.0 g) were added to a sealed tube (35 mL) in sequence. The reaction mixture was stirred at 140 oC for 12 h. Upon completion, the upper layer was removed by decantation, diluted with pentane and analyzed by an Agilent GC 7890A equipped with HP-5 column (30 m, 0.25 mm ID, 0.5 mm film) and a FID using tridecane as the internal standard. The lower layer ChCl/HCOOH was dried at room temperature under vacuum for 10 h prior to use in next cycle. The water content in the desiccated ChCl/HCOOH was determined as < 2% by a Mettler Toledo DL39 Karl Fischer Titrator. Examples see Fig. S7 (the photographs of the system during the reaction) and Fig. S8 (the carbon yield of compound 2 as a function of recycle time). To check the thermal stability of formic acid under the investigated conditions, we conducted a blank experiment. From the chromatograms which were illustrated in Fig. S9, we can see that the areas of formic acid were almost the same (15703.5 vs. 15322.9). This result indicates that the formic acid was stable under the investigated conditions. No decomposition of formic acid was noticed during the reaction. NMR and HRMS data of compounds 2 and 3 1 13 H NMR (400 MHz, CDCl3) δ 4.98 (s, 2H), 4.89 (s, 2H), 1.84 (s, 6H); C 2 NMR (100 MHz, CDCl3) δ 143.5, 113.1, 20.6. HRMS (ESI) calcd. for + C6H11 [M + H] 83.0855, found 83.0852. 1 13 O H NMR (400 MHz, CDCl3) δ 2.07 (s, 3H), 1.07 (s, 9H); C NMR (100 3 MHz, CDCl3) δ 214.4, 44.4, 26.5, 24.8. HRMS (ESI) calcd. for C6H13O [M + H]+ 101.0961, found 101.0960. S3 3. D-A reaction, dehydrogenation, and hydrolysis 3.1 D-A reactions of 2,3-dimethylbutadiene with maleic anhydride, diethyl maleate, and diethyl fumarate O O 60 oC + O O O 2 4 O 5 Compound 2 (10 mmol, 1.1 mL) and maleic anhydride (10 mmol, 0.98 g) were added to a 35 mL sealed tube. The mixture was stirred at 60 oC for 1.5 h, then cooled down to room temperature and the white solid was formed. According to the NMR data (Fig. S24 and S25), D-A product (i.e. compound 5) was obtained in a nearly quantitative yield. H CO Et CO Et 2 120 oC 2 + CO Et CO Et 2 H 2 2 7 8 Compound 2 (10 mmol, 1.1 mL) and diethyl maleate (10 mmol, 1.6 mL) were added to a 35 mL sealed tube. The mixture was stirred at 120 oC for 6 h, then cooled down to room temperature and analyzed by the Agilent GC 7890A equipped with an HP-5 column and a FID (Fig. S10a, nearly quantitative yield). It is noteworthy that the temperature exerted a significant effect on the D-A reaction. For example, the reaction did not occur at 60 oC and the starting materials still remained unchanged. Diethyl maleate cannot be completely consumed when the D-A reaction was performed at 100 oC for 12 h (Fig. S10b). H EtO C CO Et 2 120 oC 2 + CO Et CO Et 2 H 2 2 10 For comparison, we also prepared compound 10 by the D-A reaction of compound 2 and diethyl fumarate. To do this, compound 2 (10 mmol, 1.1 mL) and diethyl fumarate (10 mmol, 1.6 mL) were added to a 35 mL sealed tube. The mixture was stirred at 120 oC for 6 h, then cooled down to room temperature and analyzed by the Agilent GC 7890A equipped with an HP-5 column and a FID. As shown in Fig. S11, compound 2 and diethyl fumarate were totally converted to compound 10 (nearly quantitative yield). S4 NMR and HRMS data of D-A adducts 1 O H NMR (400 MHz, CDCl3) δ 3.38 – 3.28 (m, 2H), 2.43 (d, J = 15.1 Hz, O 2H), 2.25 (d, J = 13.9 Hz, 2H), 1.68 (s, 6H); 13C NMR (100 MHz, 5 O CDCl3) δ 174.6, 127.4, 40.5, 30.5, 19.4. HRMS (ESI) calcd. for + C10H13O3 [M + H] 181.0859, found 181.0855. 1 H H NMR (400 MHz, CDCl3) δ 4.12 (qd, J = 7.1, 1.6 Hz, 4H), 3.08 – CO2Et CO Et 2.88 (m, 2H), 2.53 – 2.32 (m, 2H), 2.30 – 2.15 (m, 2H), 1.61 (s, 6H), H 2 8 13 1.22 (t, J = 7.1 Hz, 6H).