Photooxygenation in Polystyrene Beads with Covalently and Non‐Covalently Bound Tetraarylporphyrin Sensitizers

Abstract

Two reaction protocols are described which involve the use of polymer supports as reaction media for photooxygenation processes: 1) The use of polystyrene beads (PS) loaded with tetraphenyl-(TPP) or tetratolylporphyrin (TTP), swollen with the substrate in an appropriate organic solvent and subsequent irradiation under air. Products were isolated simply by dissolution in alcoholic solvents and filtration. 2) Covalently linked tetrastyrylporphyrin in polystyrene-divinylbenzene beads were synthesized by emulsifier-free emulsion polymerization and directly used for the photooxygenation protocol described above. The latter alternative allows also the use of less polar solvents for the extraction of the oxygenation products from the polymer beads. From the sensitizer loading degree, an optimal substrate/sensitizer molar ratio of 1,000 ± 2,000 was determined and recyclization is possible for at least five times resulting in a minimum turnover number (with respect to the sensitizer TTP) of 5 Â 10 4 (after five cycles). Both approaches were applied to the ene reaction of singlet oxygen with citronellol (1), the regioisomeric pinenes 3 and 5, and the allylic alcohols 9a ± c, respectively, as well as to the [4 2]-cycloadditions of singlet oxygen to sorbinol (7) and the chiral diene 11.

Covalently immobilized porphyrins as photooxidation catalysts

“…Although juglone can be obtained by thermal conditions, 25 photooxygenation of 1,5-dihydroxynaphthalene (8) is an attractive route for its synthesis. 26 The mechanism of this reaction seems to involve 1,4-cycloaddition of singlet oxygen, formation of the corresponding 1,4-endo-peroxide (9), and decomposition into hydroperoxide (10), which oxidizes to juglone (11) (Scheme 3). 27,28 Recently described photooxidative approaches use homogeneous sensitizers in conditions of green photochemistry.…”

“…8 Noteworthy results for immobilized porphyrins were obtained with porphyrins anchored to a soluble PEG matrix 9 and with porphyrins copolymerized with polystyrene polymer. 10 The immobilization of sensitizers was recently reviewed.…”

Superior performance of macroporous over gel type polystyrene as a support for the development of photo-bactericidal materials

“…[40][41][42][43][44][45][46] The vast majority of reported systems consist of photosensitizers covalently attached (or embedded) onto the so called gel-type resins, comprised of polystyrene with very low porosity. [47][48][49] In contrast with the frequently used gel-type supports, there is another kind of resin of technological interest: macroporous resins are made of highly-crosslinked polystyrene and have the unique property of having permanent pores allowing effective mass transfer throughout the entire polymeric matrix. 39 This fact is known and used regularly in the fields of catalysis and also for separations, but has not been explored, to the best of our knowledge, in the aPDI context.…”

Homogeneous and Heterogeneous Free-Based Porphyrins Incorporated to Silica Gel as Fluorescent Materials and Visible Light Catalysts Mimic Monooxygenases

“…Numerous proposals have appeared: the use of cross-linked polymers Ribeiro et al, 2008), clays and layered materials (Bedioui, 1995;Evans & Lindsay Smith, 2001), biopolymers (Huanga et al, 2005), cationic ionexchange resins (Campestrini, S. & Meunier, 1992); silanized kaolinite (Nakagaki et al, 2004); different types of zeolites (Skrobot et al, 2003;Haber et al, 2004), modified silica (Milaeva et al, 2007), and also microporous porphyrin framework solids (Suslick et al, 2005). Noteworthy results for the immobilized porphyrins have been obtained with ionic porphyrins immobilized on cationically functionalized polystyrene (Inbaraj et al, 2003), porphyrins copolymerized with polystyrene (Griesbeck et al, 2004), a soluble polyethylene glycol-supported tetrahydroxyphenyl porphyrin (Benaglia et al, 2002), photosensitizers ionically bound at polymeric ion-exchanging resins (Gerdes et al, 2001), and a cross-linked polyacrylamide hydrogel serve as a scaffold for the photosensitizer hematoporphyrin (Rogers et al, 2005) and as well with chitosan-supported metallotetraphenylporphyrin complexes (Huanga et al, 2005). Manganese(III) 5-(pentafluorophenyl)-10,15,20-tri(2,6 dichlorophenyl)porphyrin, and manganese(II) 2,3,7,8,12,13,17,18-octachloro-5-(pentafluorophenyl)-10,15,20-tri(2,6-dichlorophenyl)porphyrin, have been covalently attached to aminopropylated silica and used in hydrocarbon oxidation by iodosylbenzene and hydrogen peroxide (Doro et al, 2000).…”