Robust Organic Photosensitizers Immobilized on a Vinylimidazolium Functionalized Support for Singlet Oxygen Generation under Continuous-Flow Conditions

Abstract

Rose Bengal was immobilized on a vinylimidazolium functionalized support, and the heterogeneous organic photosensitizer thus prepared was applied for photooxidation reactions of organic molecules under continuous-flow conditions. Substituents of the cation part of the support were found to play a crucial role in determining the lifetime of the catalyst. More than 11 days continuous operation of a flow reaction was achieved.

Key words

photooxidation - flow chemistry - organic dye - supported catalyst - Rose Bengal - continuous-flow reaction

• References and Notes

• 1 New address: K. Masuda, Interdisciplinary Research Center for Catalytic Chemistry, National Institute of Advanced Industrial Science and Technology (AIST). Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan.
• 2 DeRosa MC, Crutchley RJ. Coord. Chem. Rev. 2002; 233–234: 351
• 3 Clennan EL, Pace A. Tetrahedron 2005; 61: 6665
• 4 Ogilby PR. Chem. Soc. Rev. 2010; 39: 3181
• 5 Ohloff G. Pure Appl. Chem. 1975; 43: 481
• 6 Wasserman HH, Ives JL. Tetrahedron 1980; 37: 1825
• 7 Ghogare AA, Greer A. Chem. Rev. 2016; 116: 9994
• 8 Blossey EC, Neckers DC, Thayer AL, Schaap AP. J. Am. Chem. Soc. 1973; 95: 5820
• 9 Schaap AP, Thayer AL, Blossey EC, Neckers DC. J. Am. Chem. Soc. 1975; 97: 3741
• 10 Herrmann JM. Top. Catal. 2005; 34: 49
• 11 Su Y, Straathof NJ. W, Hessel V, Noël T. Chem. Eur. J. 2014; 20: 10562
• 12 Romero NA, Nicewicz DA. Chem. Rev. 2016; 116: 10075
• 13 Shaw MH, Twilton J, MacMillan DW. C. J. Org. Chem. 2016; 81: 6898
• 14 Plutschack MB, Pieber B, Gilmore K, Seeberger PH. Chem. Rev. 2017; 117 (18) 11796
• 15 Carofiglio T, Donnola P, Maggini M, Rossetto M, Rossi E. Adv. Synth. Catal. 2008; 350: 2815
• 16 Lumley EK, Dyer CE, Pamme N, Boyle RW. Org. Lett. 2012; 14: 5724
• 17 Dambruoso P, Ballestri M, Ferroni C, Guerrini A, Sotgiu G, Varchi G, Massi A. Green Chem. 2015; 17: 1907
• 18 Han X, Bourne RA, Poliakoff M, George MW. Chem. Sci. 2011; 2: 1059
• 19 Amara Z, Bellamy JF. B, Horvath R, Miller SJ, Beeby A, Burgard A, Rossen K, Poliakoff M, George MW. Nat. Chem. 2015; 7: 489
• 20 Peng F, Zhi P, Ji H, Zhao H, Kong F.-Y, Liang X.-Z, Shen Y.-M. RSC Adv. 2017; 7: 19948
• 21 Tobin JM, McCabe TJ. D, Prentice AW, Holzer S, Lloyd GO, Paterson MJ, Arrighi V, Cormack PA. G, Vilela F. ACS Catal. 2017; 7: 4602
• 22 Ross SD, Finkelstein M, Petersen RC. J. Am. Chem. Soc. 1960; 82: 1582
• 23 Mousavi MP. S, Kashefolgheta S, Stein A, Bühlmann P. J. Electrochem. Soc. 2016; 163: H74
• 24 Gu F, Dong H, Li Y, Si Z, Yan F. Macromolecules 2014; 47: 208
• 25 Kazemiabnavi S, Zhang Z, Thornton K, Banerjee S. J. Phys. Chem. B 2016; 120: 5691
• 26 Xue Z, Qin L, Jiang J, Mu T, Gao G. Phys. Chem. Chem. Phys. 2018; 20: 8382
• 27 Fall A. Open Org. Chem. J. 2012; 6: 21
• 28 Wilson WW, Heitz JR. J. Agric. Food Chem. 1984; 32: 615
• 29 Lambert CR, Kochevar IE. Photochem. Photobiol. 1997; 66: 15
• 30 Zakrzewski A, Neckers DC. Tetrahedron 1987; 43: 4507
• 31 Oster G, Oster GK, Karg G. J. Phys. Chem. 1962; 66: 2514
• 32 Westhead EW. Biochemistry 1965; 4: 2139
• 33 Rippa M, Picco C, Pontremoli S. J. Biol. Chem. 1970; 245: 4977
• 34 Simpson MJ, Poblete H, Griffith M, Alarcon EI, Scaiano JC. Photochem. Photobiol. 2013; 89: 1433
• 35 Alarcon EI, Poblete H, Roh HG, Couture JF, Comer J, Kochevar IE. ACS Omega 2017; 2: 6646
• 36 Catalyst preparation: To a solution of 1-vinylimidazole (0.48 mL, 5.25 mmol, 1.05 equiv) and mesitylene (ca. 0.5 mL, internal standard) in acetonitrile (50 mL), Merrifield resin (1.9 mmol/g -Cl, 2.6316 g, 5 mmol, 1.0 equiv) and NaI (37.5 mg, 0.25 mmol, 0.05 equiv) were added at room temperature. The reaction mixture was stirred (overhead stirring) under reflux condition until the consumption of the imidazole became constant (monitored by GC). After filtration, the residue was washed with acetonitrile, ethyl acetate, acetone, water, acetone, ethyl acetate and dichloromethane. Drying at 40 °C in a vacuum oven afforded the PS-vinylimidazolium support (3.0359 g, loading of imidazole: 0.674 mmol/g, determined by the consumption of imidazole). Rose Bengal (3.1246 g, 3.07 mmol, 1.5 equiv) was dissolved in pure water (250 mL), and PS-vinylimidazolium support (3.0359 g, 2.05 mmol imidazolium group, 1.0 equiv) was added to the resulting solution. This mixture was stirred at room temperature for 2 h. After filtration, the residue was washed with water, methanol, dichloromethane and finally washed with dichloromethane in a Soxhlet extractor under reflux conditions until the solvent in the extractor became colorless. Filtration and desiccation afforded the RB@PS-vinylimidazolium catalyst (3.9775 g, loading of RB: 0.12 mmol/g (determined by EDX analysis)). Continuous-flow reactions: RB@PS-vinylimidazolium catalyst (220 mg) were packed into a PTFE tube (ID: 2 mm; OD: 3 mm; L: 10 cm), with in-line filter devices for both ends. This tube was used as the column for the flow reaction. α-Terpinene was prepared as the reaction solution in 1,2-dichloroethane (0.1 mol/L, kept at 0 °C), with 0.018 mol/L pentadecane as an internal standard. This mixture (flow rate: 0.02 mL/min) was combined with air (0.5 mL/min) and introduced to the column. Three white LED bulbs were used as the light source. The reaction mixture was collected for 1 h and analyzed by GC to determine the yield. Ascaridole (1): Product was confirmed by ¹H NMR analysis of crude material and yields were determined by GC analysis. ¹H NMR (CDCl₃): δ = 6.50–6.40 (dd, J = 8.6, 33.5 Hz, 2 H, -CH=CH-), 2.04–2.00 (m, 2 H, -CH₂- near -ⁱPr), 1.96–1.89 (m, 1 H, -CH(CH₃)₂), 1.53–1.51 (d, J = 10.0 Hz, 2 H, -CH₂- near -Me), 1.38 (s, 3 H, -CH₃), 1.01–0.99 (d, J = 7.0 Hz, 6 H, -CH(CH ₃)₂). GC: R_t  = 38.5 min (50 °C: 30 min, then heating, rate: 10 °C/min to 250 °C: 10 min). p-Cymene (2): Detected by GC analysis and identified by comparison to commercial product. GC: R_t  = 24.9 min (50 °C: 30 min, then heating, rate: 10 °C/min to 250 °C: 10 min).