A Unifying Evaluation of the Technical Performances of TAML Oxidation Catalysts

Transcription

1 A Unifying Evaluation of the Technical Performances of TAML Oxidation Catalysts Matthew A. DeNardo, Matthew R. Mills, Alexander D. Ryabov*, and Terrence J. Collins* Supporting Information Table of Contents 1. Instrumentation S2 2. Materials S2 3. Synthesis of 4 S2 4. Kinetic Measurements of TAML-Catalyzed Oxidation of Orange II by H 2 O 2 S4 5. Kinetic Evaluation of 4 S4 6. Determination of k i S5 7. Supporting Information References S6 S1

2 1. Instrumentation. Spectrophotometric measurements were carried out on a Hewlett Packard Diode Array spectrophotometer (model 8452A) equipped with an automated and thermostatted 8-cell positioner. 1 H NMR data were collected at 300 K with a Bruker Avance 300 operating at 300 MHz in the indicated solvent. Chemical shifts were referenced to the previously reported residual proton solvent peak. 1 Solution ph was determined using a Corning 220 ph meter. 2. Materials. Iron TAML complexes were synthesized at Carnegie Mellon University by published methods or as described herein Synthesis of 4. The 4 synthetic route is outlined in Scheme 1S. Scheme 1S. Synthetic route for novel TAML activator 4. 2-Methyl-2-phthalimidopropanoic acid. 2-Methyl-2-phthalimidopropanoic acid was prepared as previously reported. 5 Finely ground α-aminoisobutyric acid (20 g, 194 mmol) and phthalic anhydride (35 g, 236 mmol) were placed into a 500 ml roundbottom flask and heated to 190 C until the visible formation of water vapor had ceased (approximately 45 min). The reaction mixture was allowed to cool slightly before adding the contents to 200 ml saturated NaHCO 3. The reaction flask was rinsed with 100 ml NaHCO 3 and 100 ml 1% NaOH. The combined aqueous portions were filtered and the filtrate was acidified to a ph below 2 with concentrated HCl. The resulting white precipitate was isolated by filtration and dried under vacuum at 70 C to give 39.2 g (86%) 2-methyl-2-phthalimidopropanoic acid. 1 H NMR (CDCl 3 ): 7.81 (m, 2H, ArH), 7.73 (m, 2H, ArH), 1.88 (s, 6H, CH 3 ). ESI-MS: (M-H, CH 3 OH, negative mode). Mp C, lit C 6. 2-Methyl-2-phthalimidopropanoyl chloride. This was synthesized as previously reported. 5 2-Methyl-2-phthalimidopropanoic acid (23.3 g, 0.1 mol) was weighed into a 250 ml oven-dried round-bottom flask fitted with a reflux condenser. The system was purged with argon, then SOCl 2 (36 ml, 0.5 mol) was added, and the mixture was refluxed for 1 h. After cooling to room temperature, SOCl 2 was removed under vacuum. Diethyl ether was added and removed under vacuum twice to eliminate all traces of SOCl 2. The resulting material was recrystallized from petroleum ether to yield 2-methyl-2-phthalimidopropanoyl chloride as a colorless solid (15.48 g, 61%). S2

3 1 H NMR (CDCl 3 ): 7.86 (m, 2H, ArH), 7.78 (m, 2H, ArH), 1.93 (s, 6H, CH 3 ). Mp 79 C, lit. 79 C. 6 2,3-Diamino-2,3-dimethylbutane dihydrochloride (A) was prepared as described previously with insignificant modifications. 7 2,3-Dimethyl-2,3-dinitrobutane (6 g, 34 mmol) was suspended in 100 ml concentrated HCl and the mixture was gently warmed to 50 C. Granulated tin (68.2 g, mol) was added in ca. 5 g batches at 10 min intervals, the mixture was refluxed for 2 h, cooled on ice, and KOH (16 M, 50 ml) was added dropwise via addition funnel to give a gray precipitate, which was filtered through a bed of sand and Celite. The filtrate was distilled at atmospheric pressure until the distillate was no longer basic. The distillate was acidified to ph 2 with concentrated HCl. The remaining water was removed under vacuum to yield 3.91 g of a white solid (61%). 1 H NMR (D 2 O): 1.55 (s, 6H). ESI-MS: (M+H, H 2 O, positive mode). N,N'-(2,3-Dimethylbutane-2,3-diyl)bis(2-(1,3-dioxoisoindolin-2-yl)-2- methylpropanamide) (B). 2-Methyl-2-phthalimidopropanoyl chloride (10.6 g, 42 mmol) in CH 2 Cl 2 (25 ml) was added dropwise to a solution of 2,3-Diamino-2,3- dimethylbutane dihydrochloride (A) (3.79 g, 20 mmol) and NEt 3 (20.9 ml, 150 mmol) in CH 2 Cl 2 (250 ml) at 0 C. The reaction mixture was refluxed for 2 h, allowed to cool to 25 C, and washed with KOH (1 M, 150 ml), HCl (0.01 M, 150 ml), HCl (1 M, 150 ml), and brine (150 ml) successively. The organic layer was dried with MgSO 4, filtered, and the solvent was removed under reduced pressure. The residue was dried in vacuo to give 10.7 g of a light brown, foamy solid, which was dissolved in CH 2 Cl 2 (100 ml) and passed through a silica gel plug. Evaporation of the solvent yielded B as a white solid (8.89 g, 81%). 1 H NMR (CDCl 3 ): 7.74 (m, 4H, ArH), 7.67 (m, 4H, ArH), 6.99 (s, 2H, NH), 1.70 (s, 12H, CH 3 ), 1.39 (s, 12H, CH 3 ). ESI-MS: (M-H, CH 3 CN, negative mode). N,N'-(2,3-dimethylbutane-2,3-diyl)bis(2-amino-2-methylpropanamide) (C). Hydrazine hydrate (64% hydrazine, 1.65 ml, 34 mmol) was added to a solution of N,N'-(2,3-dimethylbutane-2,3-diyl)bis(2-(1,3-dioxoisoindolin-2-yl)-2- methylpropanamide) (B) (8.89 g, 16.2 mmol) in ethanol (250 ml) at 75 C. The reaction mixture was refluxed for 18 h. The ethanol was removed under reduced pressure and HCl (2 M, 500 ml) was added to the residue. The mixture was heated to 80 C for 10 min, cooled to room temperature, filtered, and the ph of the filtrate was adjusted to 12 with solid KOH (55 g) during which the mixture turned a faint pink, then yellow. After extraction with CH 2 Cl 2 (4 150 ml) and drying with MgSO 4, solvent was removed under reduced pressure to give 4.15 g C as a white solid (73%). 1 H NMR (CDCl 3 ): 8.33 (br, 2H, NH), 1.51 (br, 4H, NH 2 ), 1.43 (s, 12H, CH 3 ), 1.33 (s, 12H, CH 3 ). ESI-MS: (M+H, CH 3 OH, positive mode). 2,2,5,5,6,6,9,9,12,12-decamethyl-1,4,7,10-tetraazacyclotridecane-3,8,11,13-tetraone (D). Triethylamine (1.23 ml, 8.8 mmol) was mixed with 20 ml THF in a 100 ml round-bottom flask. Dimethylmalonyl chloride (0.528 ml, 4 mmol) and C (1.14 g, 4 mmol) were dissolved in 20 ml THF each and placed in two syringes. These S3

4 solutions were added to the flask over 2 h at 0 C with stirring. The mixture was then warmed to ca. 25 C, stirred for 2 h, filtered, and the solvent removed under reduced pressure to give a white solid, which was recrystallized from ethyl acetate to yield D (652 mg, 43% based on C). 1 H NMR (d 6 -DMSO): 7.62 (s, 2H, NH), 5.81 (s, 2H, NH), 1.42 (s, 6H, CH 3 ), 1.30 (s, 12H, CH 3 ), 1.27 (s, 12H, CH 3 ). ESI-MS: (M+H, CH 3 OH, positive mode). Compound 4. Macrocycle D (100 mg, 0.26 mmol) was dissolved in 20 ml dry THF in a 50 ml 3-neck round-bottom flask and cooled to 0 C with an ice bath. Sodium hexamethyldisilazane (0.52 ml of a 2 M solution in THF, 1.04 mmol) was added and the mixture was stirred for 30 min to form a yellowish precipitate. Then, FeCl 3 (47 mg, 0.37 mmol) was added and the mixture was stirred for 16 h to produce a brown precipitate. The solvent was removed in vacuo and the residue was purified by column chromatography on basic alumina using CH 2 Cl 2 /MeOH/NEt 3 (90%/5%/5%) to give 4 as an orange solid (45 mg, 31%). ESI-MS: 434 (M, MeOH, negative mode). This is the expected mass of the anionic complex without axial ligands. Anal. Calcd. for Na[Fe III {(Me 2 CNCOCMe 2 NCO) 2 CMe 2 }NMe 3 ]: C, 53.76; H, 8.12; N, 12.54%: Found C, 53.32; H, 7.72; N, Kinetic Measurements of TAML-Catalyzed Oxidation of Orange II by H 2 O 2. Stock solutions of catalysts 1, 2, and 4 of ca. (0.5 5) 10-5 M were prepared in HPLC grade methanol. Stock solutions of Orange II were prepared in HPLC grade water. Solutions of H 2 O 2 ( M) were made in ph M phosphate buffer (using a Corning 220 ph meter) and standardized daily by measuring the absorbance in water at 230 nm (ε = 72.8 M -1 cm -1 ). 8 In a polymethylmethacrylate UV-vis cuvette, the stock solution of Orange II was added to an appropriate amount of 0.01 M, ph 7 phosphate buffer at 25 C to give a (5 50) 10-6 M solution followed by the addition of 20 µl of a catalyst stock solution of appropriate concentration to achieve the desired catalyst concentration in the range of (0.1 1) 10-6 M. For experiments in which catalyst concentration was varied the appropriate amount of catalyst stock solution was added followed by an appropriate amount of methanol to bring the total volume of methanol added to 20 µl. The appropriate volume of the stock solution of H 2 O 2 was added to initiate the reaction. Initial rates of Orange II oxidation were calculated as the average of at least three measurements using an extinction coefficient of 18,100 M -1 cm -1 at 485 nm. All calculations were made using the Sigma Plot package (versions 12.0 and 12.5). 5. Kinetic Evaluation of 4. The catalytic activity of 4 was evaluated using H 2 O 2 as an oxidant and Orange II as a substrate. At ph 7 the catalysis was probed in the oxidant concentration range of ( ) 10-3 M due to noticeably lower activity of 4 compared to TAMLs 1 and 2. Initial rates of Orange II bleaching were a linear function of [4] in this range as shown in Figure 1S suggesting no appreciable aggregation. A hyperbolic dependence of the rate on H 2 O 2 concentration as shown in Figure 2S in agreement with the reaction mechanism in Scheme 1 and the corresponding Equation 1. The initial rate is practically independent of the H 2 O 2 loading at [H 2 O 2 ] = M. As is indicated in the inset to Figure 2S, here [ ] = S4

5 [Fe ][Orange II] as k I [H 2 O 2 ] >>k II [S] (Equation 3). The rate constants k I and k II were obtained by fitting the data in Figure 2S to Equation 1. Additionally, k II was calculated from the slope of the line in the inset to Figure 2S in accordance with Equation 3. The two values of k II so obtained are nearly identical. Measurements of k I and k II were performed at ph 7 and 11, 11. Figure 1S. Initial rates of degradation of the azo dye Orange II as a function of [4] in ph M phosphate buffer at 25 C. [H 2 O 2 ] = M, [Orange II] = M. Figure 2S. Initial rate of 4-catalyzed bleaching of Orange II by hydrogen peroxide as a function of [H 2 O 2 ] at [Orange II] = M. The solid line was calculated using the equation in Scheme 1to give the rate constants in Table 1. Inset shows the rate dependence on [Orange II] at M H 2 O 2. Other conditions: [4] M, ph 7 (0.01 M phosphate), 25 C. 6. Determination of k i. The effective values of k i for activators 1, 2, and 4 were calculated using Equation 4 (main text) which, as it has been recently demonstrated 9, holds under all conditions provided H 2 O 2 is present in a large excess relative to S5

6 substrate. To ensure incomplete bleaching, minimal catalyst concentrations of ca and 10-7 M for TAML families 1 and 2, respectively were employed. Measurements for 4 were made at higher concentrations of ca M. It was previously proven for 1 under basic conditions (ph 11) that effective values of k i are essentially independent of TAML concentration. 10 The same was confirmed in this work (Figure 3S). Effective values of k i were observed to be weakly dependent on catalyst concentration in a 10-fold range around the concentrations identified above. Figure 3S. Rate constant for inactivation of 1c, k i, in the bleaching of Orange II ( M) as a function [1c] in ph M phosphate buffer at 25 C. Supporting Information References (1) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem. 1997, 62, (2) Ghosh, A., Dissertation, Carnegie Mellon, Pittsburgh, (3) Sen Gupta, S., Dissertation, Carnegie Mellon, Pittsburgh, (4) Ellis, W. C.; Tran, C. T.; Denardo, M. A.; Fischer, A.; Ryabov, A. D.; Collins, T. J. J. Am. Chem. Soc. 2009, 131, (5) Ghosh, A.; Ramidi, P.; Pulla, S.; Sullivan, S.; Collom, S.; Gartia, Y.; Munshi, P.; Biris, A.; Noll, B.; Berry, B. Catal. Lett. 2010, 137, 1. (6) Al-Hassan, S. S.; Cameron, R. J.; Curran, A. W. C.; Lyall, W. J. S.; Nicholson, S. H.; Robinson, D. R.; Stuart, A.; Suckling, C. J.; Stirling, I.; Wood, H. C. S. J. Chem. Soc., Perkin Trans , (7) Sayre, R. J. Am. Chem. Soc. 1955, 77, (8) George, P. Biochem. J. 1953, 54, 267. (9) Emelianenko, M.; Torrejon, D.; Denardo, M. A.; Ryabov, A. D.; Collins, T. J. J. Math. Chem. 2014, 52, (10) Chanda, A.; Ryabov, A. D.; Mondal, S.; Alexandrova, L.; Ghosh, A.; Hangun-Balkir, Y.; Horwitz, C. P.; Collins, T. J. Chem. Eur. J. 2006, 12, S6