doi.org/10.26434/chemrxiv.12622307.v1

Organic Photoredox-Catalyzed Cycloadditions Under Single-ChainPolymer ConfinementJacob Piane, Lauren Chamberlain, Lucas T. Alameda, Ashley Hoover, Elizabeth Elacqua

Submitted date: 07/07/2020 • Posted date: 08/07/2020Licence: CC BY-NC-ND 4.0Citation information: Piane, Jacob; Chamberlain, Lauren; Alameda, Lucas T.; Hoover, Ashley; Elacqua,Elizabeth (2020): Organic Photoredox-Catalyzed Cycloadditions Under Single-Chain Polymer Confinement.ChemRxiv. Preprint. https://doi.org/10.26434/chemrxiv.12622307.v1

Cooperative catalysis enables synthetic transformations that are not feasible using monocatalytic systems.Such reactions are often diffusion controlled and require multiple catalyst interactions at high dilution. Wedeveloped a confined dual-catalytic polymer nanoreactor that enforces catalyst co-localization to enhancereactivity in a fully-homogeneous system. The photocatalyzed-dimerization of substituted styrenes isdisclosed using confined-single-chain polymers bearing triarylpyrylium-based pendants, with pyrene as anelectron relay catalyst. Enhanced reactivity with low catalyst loadings was observed compared tomonocatalytic polymers with small-molecule additives. Our approach realizes a dual-catalytic single-chainpolymer that provides enhanced reactivity under confinement, presenting a further approach fordiffusion-limited-photoredox catalysis.

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Organic Photoredox-Catalyzed Cycloadditions Under Single-Chain Polymer Confinement Jacob J. Piane, Lauren E. Chamberlain, Lucas T. Alameda, Ashley C. Hoover, and Elizabeth Elacqua*

Department of Chemistry, The Pennsylvania State University, University Park PA, 16802, USA

ABSTRACT: Cooperative catalysis enables synthetic transformations that are not feasible using monocatalytic systems. Such reactions are often diffusion controlled and require multiple catalyst interactions at high dilution. We developed a confined dual-catalytic polymer nanoreactor that enforces catalyst co-localization to enhance reactivity in a fully-homogeneous system. The photocatalyzed-dimerization of substituted styrenes is disclosed using confined-single-chain polymers bearing triarylpyrylium-based pendants, with pyrene as an electron relay catalyst. Enhanced reactivity with low catalyst loadings was observed compared to monocatalytic polymers with small-molecule additives. Our approach realizes a dual-catalytic single-chain polymer that provides enhanced reactivity under confinement, presenting a further approach for diffusion-limited-photoredox catalysis.

Compartmentalization is one of Nature’s design principles: en-zymes are shielded from incompatible environments and parti-tioned such that cooperative functions like catalysis are opti-mized. Confined-space effects in catalysis have also been re-ported with organic molecules and porous materials (e.g., cu-curbit[n]urils, metal-organic frameworks (MOFs), and metal-organic cages (MOCs)). Systems like MOFs or MOCs provide distinct benefits, including periodic arrangements of transition metal catalysts that facilitate increased local concentrations of reactive species,1 thus, accelerating the rate of organic reac-tions. Localized rate enhancement is also observed in molecu-lar systems, such as the hydrogen-binding Rebek’s softball, in which reactive species diffused toward a catalytic center allow-ing for a 200-fold rate enhancement.2 In close analogy to Na-ture, these supramolecular frameworks also aid in stabilization of different conformations. Raymond’s M4L6 cluster,3 for ex-ample, has a unique interior microenvironment that lowers en-tropic barriers to reactivity, while enthalpically favoring com-pact transition states that are not observable in bulk solution.

Recently, sunlight-enabled-photocatalysis has emerged as a pillar for synthesis,4-6 particularly for C—C and C—N bond construction while exploiting mild reaction conditions. Com-monly-employed photocatalysts (PCs) are based upon iridium or ruthenium metal complexes and organic dyes that feature long excited-state lifetimes, high redox potentials, and strong visible absorption. Dual photoredox catalysis enables challeng-ing transformations that cannot be achieved with either catalyst alone.7 The merger of photoredox with transition metal cataly-sis has achieved multiple C—H activation reactions with Pd,8 as well as trifluoromethylation,9 difunctionalization,10 and other strategies with copper co-catalysts.11 Much interrogation into dual photoredox/Ni catalysis has unleashed potent sp3—sp2 cross-coupling methods from the groups of MacMillan,12, 13 Doyle,14 and Molander,15, 16 including decarboxylative and or-ganoboron couplings.17 Additional strategies by Yoon and coworkers have interrogated Bronsted and Lewis acids as co-catalysts for metallaphotoredox-mediated [2+2] cycloaddition

reactions, leading to high control over product chirality.18-20 Further, Nicewicz has pioneered a photoredox/electron relay co-catalysis system for [2+2] dimerizations to realize natural lignan-based cyclobutanes.21

The efficiency of co-catalytically-powered reactions relies on proximal catalyst locations, a bottleneck difficult to control with the degrees of freedom often afforded in solution-phase chemistry. In addition, challenges remain in optimization, as expensive PCs can be loaded at amounts exceeding maximum solubility.22 Strategies to circumvent these limitations in heter-ogeneous photoredox catalysis have been realized using MOFs and quantum dots (QDs) by the groups of Lin and Weix,23 re-spectively. While the MOF confines Ir- and Ni-catalytic com-ponents within 0.6 nm of each other24 and facilitates electron and radical transfers between them that allows for efficient turn-over, the QDs were highly effective at extremely low loadings.

Considering the successful heterogeneous dual catalysis in MOFs, we hypothesized that single-chain polymer nanoparti-cles (SCNPs)25 could provide a versatile platform to drive ho-mogeneous dual catalysis within nanoreactors. The SCNP would provide several advantages, including controlled catalyst loadings, solubility, and well-defined crosslinking that enables co-localization of cooperative catalysts. Herein, we disclose a triarylpyrylium (TPT)-based polymer that functions as an or-ganic single-electron oxidant/electron relay nanoreactor. Our design features a styrylpyrene (SP) monomer that acts as both a covalent crosslink26 to generate the confined environment, but also as a functioning electron relay (ER) for photoredox-cata-lyzed stereospecific [2+2] cycloadditions. Our TPT-SP-based nanoreactor operates in low loadings of both the photocatalyst and ER (1 mol % TPT, 0.67 mol % ER), and demonstrates en-hanced reactivity in comparison to monocatalytic polymer ana-logues. We attribute these results to efficient colocalization of the PC and ER, owing to confinement.

Our motivation lies in developing versatile and efficient ho-mogeneous catalysts. In studies to realize co-catalytically-ac-tive polymers for sustainable chemistry, we noted that SCNPs

whose folding featured metal crosslinks27 had demonstrated reasonable catalytic activity in reactions such as oxidations and cross-couplings.25 Further reports by Zimmerman identified a single-chain polymeric ‘Clickase’ that accelerates copper-click reactions.28 Given the success of these monocatalytic systems, combined with recent reports of enhanced reactivity,28 we intu-ited that a SCNP comprising another catalyst could promote ac-celerated reactions under confinement if the crosslink could ad-ditionally act as an organocatalyst. Recognizing the potential of pyrene to act as an ER catalyst, we designed SCNPs bearing strongly-oxidizing TPT and pyrene to study the effects of con-fining two cooperative catalysts in close proximity. Photocata-lyzed-[2+2] cycloadditions are reported with electron-rich sty-renes29, 30 When strongly oxidizing photocatalysts are em-ployed, cycloreversion of the resulting cycloadduct can pre-dominate and shift the equilibrium of this reaction towards the starting alkene. The addition of a polyaromatic electron relay catalyst circumvents oxidative cycloreversion by acting as the active oxidant with a lower potential that is not sufficient to ox-idize the cyclized product.21 Specifically, the potent photooxi-dant first oxidizes the ER catalyst, which subsequently oxidizes the substrate. Honing in on the interaction between the two cat-alysts, we hypothesized that confining the photoredox catalyst and ER within the same polymer backbone would enhance the kinetics of single-electron transfer.

Scheme 1: Schematic depicting TPT-SP-polymer synthesis and individual polymer characterization information.

Triarylpyrylium salts are easily prepared with a diverse range of functionalities at the aryl positions, providing access to pho-tocatalysts with varying electronic properties. This facilitates tuning excited-state redox potentials. Methacrylate-derived pyrylium monomers were prepared according to previous re-ports.31 Methyl methacrylate (MMA) was selected as the back-bone in order to maintain solubility in common organic sol-vents. With the desired monomers in hand, statistical copoly-mers comprising TPT-methacrylate, SP-methacrylate, and MMA were prepared with targeted incorporation of 90:5:5 [MMA]:[TPT]:[SP]. Polymers were synthesized using reversi-ble-addition fragmentation chain-transfer (RAFT) polymeriza-tion (Scheme 1). 1H-NMR spectroscopic characterization con-firmed a 6% incorporation of TPT and 4% incorporation of SP. The polymer molecular weight was determined to be 12 kDa through size exclusion chromatography (SEC). SEC also con-firmed that the polymers were well-defined (Đ = 1.45) (Figure 1).

Figure 1: (top) SEC overlay and (bottom) UV/Vis spectral overlay of TPT-SP-polymer (red) and SCNP (blue, secondary axis).

Cross-linking of styrylpyrene residues was achieved by irra-diation of linear polymer solutions in MeCN (10 mg/mL) with a white compact fluorescent lamp. Dimerization of styrylpyrene and nanoparticle formation was characterized by UV/Vis spec-troscopy, wherein disappearance of the characteristic styrenyl absorbance (λ = 391 nm) and concomitant appearance of cyclo-butane features at λ = 333 nm and 352 nm were observed (Fig-ure 1). SEC confirmed primarily intramolecular cross-linking with a small increase in apparent molecular weight to 14 kDa and dispersity of 1.35 (Figure 1). Trans-anethole was selected as a model system to study the

[2+2] cyclodimerization using the SCNP (Figure 2), given prior reports of TPT-catalyzed single-electron oxidant-electron relay photocatalysis in the cyclodimerization of anethole.21 In a typi-cal experiment, the styrenic small molecule was added to a so-lution of the SCNP (0.0004 mmol loading, which corresponds to 1.0 mol% TPT) in MeCN, and was irradiated with 427 nm Kessil LEDs at 25% light intensity (approximate light-to-vial distances of ~7.5 cm), with conversion monitored using 1H NMR spectroscopy. After evaluating several solvents, MeCN was found to provide the highest yield (See SI). This was at-tributed to increased solubility of the polymer and high dielec-tric constant. When using the confined TPT-SCNP photocata-lyst bearing the pyrene-based ER, a 66% yield of the dimerized product was observed within 24 hours. Increasing the concen-tration to 0.4 M gave moderate improvements of yield (71%, Table S-1), while further changes adversely affected product formation. Altering the photocatalyst concentration and in-creasing light intensity decreased yield. The pyrylium family of photoredox catalysts is prone to photobleaching and

0.0

0.2

0.4

0.6

0.8

1.0

7.0 8.0 9.0 10.0

Nor

mal

ized

Inte

nsity

Time (min)

dimerization of the pyranyl radical;32, 33 accordingly, longer re-action times did not yield more product, likely because the amount of active pyrylium in solution decreases over time. Re-actions conducted without any TPT-SCNP or in the absence of light yielded no cycloadduct.

Figure 2: [2+2] Cycloadditions of styrenyl derivatives through TPT-SCNP-catalyzed photoinduced-electron transfer.

Typically, visible-light-organocatalyzed [2+2] cyclodimeri-zations proceed in a sluggish manner, often over 48+ hours, and reported TPT-catalyzed cycloadditions similarly plateau in con-version over days. Thus, we sought to further investigate the SCNP system and elucidate the effect of confinement. Given the optimized results suggested that the photocatalyzed cy-cloaddition proceeded with ease, control experiments were con-ducted using monocatalytic polymers and compared with the dual catalytic SCNPs (Table 1). We synthesized copolymers of MMA with TPT-methacrylate or SP-methacrylate. Both poly-mers were prepared by RAFT polymerization using the same procedure as for the target co-catalytic polymer. Proton NMR spectroscopy indicated 1.83% incorporation of TPT and 0.68% incorporation of SP in TPT-co-MMA and SP-co-MMA, respec-tively (Scheme 1). The molecular weight of the TPT copolymer was determined to be 18 kDa using SEC in THF, with a disper-sity of 1.17. The molecular weight of the SP copolymer was determined to be 21.5 kDa, with a dispersity of 1.02. Similar to the co-catalytic SCNP, the SP-co-MMA monomer was cross-linked to mimic a confined network, denoted SP-SCNP.

With the monocatalytic polymers in hand, we attempted to catalyze the [2+2] cycloaddition of trans-anethole with TPT-co-MMA in the absence of the ER. Using the same optimized conditions resulted in 2% of the desired product (and recovering mostly starting material) after 24 hours, suggesting either the presence of the ER or the confined interior is critical. Further, irradiation of trans-anethole with TPT-co-MMA as the PC in the presence of pyrene as a small-molecule additive, similarly resulted in trace amounts of cyclobutane adduct. These results suggested confinement was a significant design element and led to accelerated rates and higher conversion when using the SCNP. We, thus investigated the possibility that SP-SCNP could similarly function as a nanoreactor, providing small mol-ecule TPT and the reactant could efficiently diffuse toward the ER for co-catalysis. This reaction afforded the desired product in 10% yield after 24 hours, while the same reaction in the ab-sence of TPT gave none of the desired product. Further, when

the TPT-co-MMA polymer and SP-SCNP polymers were used together as co-catalysts, trace amounts of product were ob-served. The collective results confirm the presence of both the TPT and ER catalysts are necessitated within the same single-chain polymer system and importantly, the improved yields and acceleration in rate is, indeed, a result of polymer confinement and subsequent co-localization of TPT and the pyrene ER within the nanoreactors. Table 1: Comparison of monocatalytic polymer systems with small-molecule ER or TPT in the [2+2]dimerization of ane-thole.

Upon seeing the effects of dual catalyst confinement in the dimerization of anethole, we looked to additional styrenyl de-rivatives for [2+2] cycloaddition. Dimerization of 4-meth-oxystyrene was also possible up in 26% yield. In this case, competition with the formation of poly(4-methoxy)styrene oc-curred at room temperature, given methoxystyrene’s reported cationic polymerization using TPT.34 Additionally, α-asarone was cyclized to give the natural product (±) Magnosalin in 49% yield. More challenging electron-deficient vinyl arenes did not undergo the desired transformation.

Figure 3: [2+2] Cross-dimerization of anethole with styrene.

We sought to further investigate the versatility and compati-bility of our SCNP with cross [2+2] cycloadditions. (Figure 3). The cyclization of trans-anethole and styrene was used as a model system. Optimal conditions for the [2+2] cross-cycload-dition were found using 1.5 equivalents of styrene (See SI). Us-ing our co-catalytic SCNPs, the cross product was obtained in 44% yield with 22% of the dimer with 1 mol% SCNP with re-spect to TPT. Similar controls were conducted using the [2+2] cross-dimerization system to probe the effects of confinement (Table 2).

Using TPT-co-MMA without any electron relay catalyst re-sulted in 5% of the desired product, with 3% of the trans-ane-thole dimer as the major byproduct. The addition of pyrene to this system resulted in trace amounts of the cross product and of the dimer. SP-co-MMA with TPT as a co-catalyst gave the cross-dimerized product in 1% yield with 2% of the dimer. The separate polymers SP-SCNP and TPT-co-MMA as co-catalysts afforded 5% of the desired product and 3% of the byproduct, further highlighting the diffusion limitations present with mon-ocatalytic polymers.

Table 2: Comparison of monocatalytic polymer systems with small-molecule ER or TPT in [2+2]cross-dimerizations with anethole.

We demonstrate that a dual-catalytic single-chain polymer

system bearing both photocatalyst and electron relay catalyst functions as an efficient homogeneous photoredox catalyst un-der confinement. Our investigations have highlighted that the proximity of the catalysts improves the efficiency of the co-cat-alyzed [2+2] cycloaddition compared with the analogous reac-tion using separate polymeric catalytic components. The en-hanced reactions are attributed to improved efficiency of SET between the photocatalyst and the electron relay within the compartmentalized SCNP. The versatility of the photoredox SCNP-catalyst was demonstrated through both cross-dimeriza-tions with styrene, and the synthesis of the natural product (±) Magnosalin using low catalyst loadings. Future work will look interrogate other organo-photoredox catalysis with efforts to-ward tackling diffusion limitations.

ASSOCIATED CONTENT Supporting Information Small-molecule and polymer experimental procedures, spectro-scopic characterization, optimization tables (PDF)

AUTHOR INFORMATION Corresponding Author * elizabeth.elacqua@psu.edu

Author Contributions The manuscript was written through contributions of all authors.

ACKNOWLEDGMENT

This work was supported by start-up funds generously provided by the Pennsylvania State University. We acknowledge Joey Cotruvo and Christian Pester for the use of instruments, and we thank Eric Nacsa for helpful discussions.

REFERENCES 1. Mouarrawis, V.; Plessius, R.; van der Vlugt, J. I.; Reek, J. N. H., Front. Chem. 2018, 6 (623). 2. Kang, J.; Rebek, J., Nature 1997, 385 (6611), 50-52. 3. Caulder, D. L.; Powers, R. E.; Parac, T. N.; Raymond, K. N., Angew. Chem. Int. Ed. 1998, 37 (13-14), 1840-1843. 4. Dhakshinamoorthy, A.; Li, Z.; Garcia, H., Chem. Soc. Rev. 2018, 47 (22), 8134-8172.

5. Romero, N. A.; Nicewicz, D. A., Chem. Rev. 2016, 116 (17), 10075-10166. 6. Feng, Z.; Zeng, T.; Xuan, J.; Liu, Y.; Lu, L.; Xiao, W. J., Sci. China: Chem. 2016, 59, 171. 7. Skubi, K. L.; Blum, T. R.; Yoon, T. P., Chem. Rev. 2016, 116 (17), 10035-10074. 8. Kalyani, D.; McMurtrey, K. B.; Neufeldt, S. R.; Sanford, M. S., J. Am. Chem. Soc. 2011, 133 (46), 18566-18569. 9. Ye, Y.; Sanford, M. S., J. Am. Chem. Soc. 2012, 134 (22), 9034-9037. 10. Reed, N. L.; Herman, M. I.; Miltchev, V. P.; Yoon, T. P., Org. Lett. 2018, 20 (22), 7345-7350. 11. Hossain, A.; Bhattacharyya, A.; Reiser, O., Science 2019, 364 (6439), eaav9713. 12. Noble, A.; McCarver, S. J.; MacMillan, D. W. C., J. Am. Chem. Soc. 2015, 137 (2), 624-627. 13. Nicewicz, D. A.; MacMillan, D. W. C., Science 2008, 322 (5898), 77. 14. Zuo, Z.; Ahneman, D. T.; Chu, L.; Terrett, J. A.; Doyle, A. G.; MacMillan, D. W. C., Science 2014, 345 (6195), 437. 15. Jouffroy, M.; Primer, D. N.; Molander, G. A., J. Am. Chem. Soc. 2016, 138 (2), 475-478. 16. Gutierrez, O.; Tellis, J. C.; Primer, D. N.; Molander, G. A.; Kozlowski, M. C., J. Am. Chem. Soc. 2015, 137 (15), 4896-4899. 17. Tellis, J. C.; Primer, D. N.; Molander, G. A., Science 2014, 345 (6195), 433. 18. Sherbrook, E. M.; Jung, H.; Cho, D.; Baik, M.-H.; Yoon, T. P., Chem. Sci. 2020, 11 (3), 856-861. 19. Daub, M. E.; Jung, H.; Lee, B. J.; Won, J.; Baik, M.-H.; Yoon, T. P., J. Am. Chem. Soc. 2019, 141 (24), 9543-9547. 20. Yoon, T. P., Acc. Chem. Res. 2016, 49 (10), 2307-2315. 21. Riener, M.; Nicewicz, D. A., Chem. Sci. 2013, 4 (6), 2625-2629. 22. Jespersen, D.; Keen, B.; Day, J. I.; Singh, A.; Briles, J.; Mullins, D.; Weaver, J. D., Org. Process Res. Dev. 2019, 23 (5), 1087-1095. 23. Caputo, J. A.; Frenette, L. C.; Zhao, N.; Sowers, K. L.; Krauss, T. D.; Weix, D. J., J. Am. Chem. Soc. 2017, 139 (12), 4250-4253. 24. Zhu, Y.-Y.; Lan, G.; Fan, Y.; Veroneau, S. S.; Song, Y.; Micheroni, D.; Lin, W., Angew. Chem. Int. Ed. 2018, 57 (43), 14090-14094. 25. Rothfuss, H.; Knöfel, N. D.; Roesky, P. W.; Barner-Kowollik, C., J. Am. Chem. Soc. 2018, 140 (18), 5875-5881. 26. Frisch, H.; Menzel, J. P.; Bloesser, F. R.; Marschner, D. E.; Mundsinger, K.; Barner-Kowollik, C., J. Am. Chem. Soc. 2018, 140 (30), 9551-9557. 27. Knöfel, N. D.; Rothfuss, H.; Willenbacher, J.; Barner-Kowollik, C.; Roesky, P. W., Angew. Chem. Int. Ed. 2017, 56 (18), 4950-4954. 28. Chen, J.; Wang, J.; Li, K.; Wang, Y.; Gruebele, M.; Ferguson, A. L.; Zimmerman, S. C., J. Am. Chem. Soc. 2019, 141 (24), 9693-9700. 29. Ischay, M. A.; Ament, M. S.; Yoon, T. P., Chem. Sci. 2012, 3 (9), 2807-2811. 30. Ischay, M. A.; Lu, Z.; Yoon, T. P., J. Am. Chem. Soc. 2010, 132 (25), 8572-8574. 31. García-Acosta, B.; García, F.; García, J. M.; Martínez-Máñez, R.; Sancenón, F.; San-José, N.; Soto, J., Org. Lett. 2007, 9 (13), 2429-2432. 32. Kawata, H.; Niizuma, S., Bull. Chem. Soc., Jpn. 1989, 62 (7), 2279-2283. 33. Conrow, K.; Radlick, P. C., J. Org. Chem. 1961, 26 (7), 2260-2263. 34. Perkowski, A. J.; You, W.; Nicewicz, D. A., J. Am. Chem. Soc. 2015, 137 (24), 7580-7583.

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S-1

Organic Photoredox-Catalyzed Cycloadditions Under Single-Chain Polymer Confinement Jacob J. Piane, Lauren E. Chamberlain, Lucas T. Alameda, Ashley C. Hoover, and Elizabeth Elacqua*

Department of Chemistry, The Pennsylvania State University, University Park, PA 16802

elizabeth.elacqua@psu.edu

_______________________________________________________________________ Supporting Information Materials and Methods. All chemicals were purchased from Sigma Aldrich, Alfa Aesar, Oakwood Chemicals, or TCI America, and used as received unless otherwise indicated. NMR spectroscopic characterization was conducted on a Bruker Avance 500 or 400 MHz spectrometer using CDCl3 unless otherwise indicated. Chemical shifts are reported in ppm, and referenced to residual CHCl3. Trioxane was utilized as an internal standard for conversion and yields of small-molecule transformations. Polymer molecular weights and dispersities were measured using a TOSOH EcoSEC HLC-8320 GPC, coupled UV and RI detectors, controlled by an EcoSEC-WS program, and calibrated with poly(styrene) standards. The column and guard column utilized were pre-packed from TOSOH in THF (TSKgel GMHHR-H; mixed bed column, 7.8 nm I.D. x 30 cm) and the column temperature was maintained at 24 °C. All samples were measured with a mobile phase consisting of THF (Sigma-Aldrich, HPLC grade, inhibitor free). The injection volume was 8 µL and the flow rate was 1 mL min-1. UV-visible absorption spectra were obtained on an Agilent Cary 60 UV-visible spectrophotometer (Agilent Technologies, Inc) using a quartz cuvette (Starna Cells). Polymer solutions for UV-Vis analysis were prepared in acetonitrile (Sigma-Aldrich, HPLC grade). Photoredox experiments were conducted using Kessil LED photoredox lights (427 nm; PR160) using either 20 mL scintillation vials or 1 dram vials pending reaction scale. All reactions were irradiated using two LED lights with a vial-to-lamp distance of approximately 7.5 cm and a cooling fan positioned either adjacent to the reactions (household desk fan) or above the reactions (Kessil PR160 rig with fan kit: http://www.kessil.com/photoreaction/PR160Rig.php). Kessil PR160L LED lamps were not found to significantly alter yield.

S-2

Synthesis of TPT

Scheme S-1: Synthetic route for the photocatalyst TPT-based monomer 4-formylphenyl methacrylate (3) 1 (6.11 g, 50 mmol) was dissolved in 50 mL of DCM. 7.7 mL of triethylamine was added to the solution, and the resulting mixture was cooled to 0 °C. 2 (5.4 mL, 55 mmol) was added dropwise to the mixture with stirring. The reaction was stirred at room temperature for 24 hrs. The reaction mixture was extracted with water (3 x 50 mL) and brine (2 x 50 mL). The organic layer was dried over anhydrous Na2SO4 and concentrated. The resulting product was purified via flash chromatography (5-10% EtOAc/Hex) to yield 8.65 g (91%) of 3 as a clear gel. 1H NMR (400 MHz, CDCl3) δ 10.00 (s, 1H), 7.93 (d, J = 8.59 Hz, 2H), 7.31 (d, J = 8.52 Hz, 2H), 6.38 (s, 1H), 5.81 (s, 1H), 2.07 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 191.14, 165.29, 155.85, 135.60, 134.12, 131.39, 128.31, 122.61, 18.50.

S-3

Figure S-1: 1H NMR spectrum of 3 (CDCl3, 400 MHz).

*

S-4

Figure S-2: 13C NMR spectrum of 3 (CDCl3, 125 MHz). 4-(4-(methacryloyloxy)phenyl)-2,6-diphenylpyrylium tetrafluoroborate (4) 3 (8.65 g, 45.5 mmol) and acetophenone (13.3 mL, 113.8 mmol) were dissolved in 45 mL of DCM. Boron trifluoride diethyl etherate (14.6 mL, 118.3 mmol) was added dropwise to the mixture with stirring. The reaction was heated to 50 °C under reflux and stirred for 24 hrs. The resulting reaction mixture was cooled to room temperature and the product was precipitated in diethyl ether (100 mL). The product was collected by filtration and washed with diethyl ether (3 x 25 mL) to yield 6.07 g (29%) of 4 as a dark yellow solid. 1H NMR (400 MHz, CDCl3) δ 8.62 (s, 2H), 8.38 (m, 6H), 7.74 (m, 6H), 7.38 (d, J = 8.81, 2H), 6.30 (s, 1H), 5.80 (s, 1H), 2.02 (s, 3H). 13C (125 MHz, CDCl3) δ 170.64, 135.70, 132.04, 130.50, 128.85, 128.72, 123.73, 114.47, 18.43.

*

S-5

Figure S-3: 1H NMR spectrum of 4 (CDCl3, 400 MHz)

*

S-6

Figure S-4: 13C NMR spectrum of 4 (CDCl3, 125 MHz).

*

S-7

Synthesis of SP

Scheme S-2: Synthetic route for the electron relay SP Compounds 7, 10 and 11 were synthesized as previously described in the literature (ref: Frisch, H.; Menzel, J. P.; Bloesser, F. R.; Marschner, D. E.; Mudsinger, K.; Barner-Kowollik, C. J. Am. Chem. Soc. 2018, 140, 9551-9557.) (E)-4-(2-(pyren-1-yl)vinyl)phenol (7) 5 (4.05 g, 14.4 mmol,) and Pd(OAc)2 (0.135 g, 0.60 mmol) were dissolved in triethanolamine (60 mL). 6 (1.82 mL, 12.0 mmol) was added and the reaction mixture was stirred at 100 oC for 17 hours. The reaction mixture was then cooled and diluted with 30 mL each of water and EtOAc. The mixture was filtered through a plug of celite and then extracted with EtOAc (2 x 30 mL) and washed with water (2 x 30 mL) and brine (30 mL). The organic layer was dried over anhydrous Na2SO4 and concentrated. The resulting solid was recrystallized in DCM to yield 1.026 g (27%) of 7 as a powder. 1H NMR (400 MHz, CDCl3) δ 8.49 (d, J = 9.30, 1H), 8.30 (d, J = 8.09, 1H), 8.19-8.16 (m, 3H), 8.13 (d, J = 9.28, 1H), 8.08-8.04 (m, 3H), 8.00 (t, J = 7.2, 1H), 7.59 (d, J = 8.51, 2H), 7.30 (d, J = 16.02, 1H), 6.91 (d, J = 8.54, 2H), 4.80 (s, 1H).

S-8

Figure S-5: 1H NMR spectrum of 7 (CDCl3, 400 MHz). 2-(methacryloyloxy)ethyl 5-bromopentanoate (10) DMAP (0.305 g, 2.5 mmol), 9 (2.43 mL, 20 mmol) and triethylamine (5.3 mL)were dissolved in 30 mL of THF and cooled to 0°C. 8 (3.36 mL, 25 mmol) was dissolved in 10 mL of THF and added dropwise to the reaction mixture. THF (10mL) was used to ensure complete transfer of 8. The reaction was stirred at 0°C for 1hr and then warmed to room temperature and stirred for an additional 30 min and then concentrated. The contents of the flask were diluted with EtOAc (250 mL) and washed with water (2 x 50 mL), NaHCO3 (2 x 50 mL) and brine (1 x 50 mL). The organic layer was died over anhydrous Na2SO4 and concentrated. The resulting product was purified via flash chromatography (0-5-20-100% EtOAc/Hex) to yield 4.12g (78%) of 10 as a clear oil. 1H NMR (400 MHz, CDCl3) δ 6.08 (s, 1H), 5.55 (m, 1H), 4.29 (m, 4H), 3.36 (t, J = 6.56 2H), 2.33 (t, J = 7.23 2H), 1.90 (s, 3H), 1.88-1.82 (m, 2H), 1.78-1.71 (m, 2H).

*

S-9

Figure S-6: 1H NMR spectrum of 10 (CDCl3, 400 MHz). 2-(methacryloyloxy)ethyl (E)-5-(4-(2-(pyren-1-yl)vinyl)phenoxy)pentanoate (11) 7 (1.037 g, 3.24 mmol) and 10 (1.54 g, 5.83 mmol) were dissolved in MeCN (50 mL). Cs2CO3 (1.90 g, 5.83 mmol) was added and the reaction mixture was sparged with N2 for 20 min. The reaction was stirred under N2 at 45 °C for 24 hrs. The reaction mixture was cooled to room temperature and filtered. The filtrate was diluted with MeOH (150 mL) and placed in the freezer. The product was filtered off to yield 1.131g (74%) of 11 as a bright yellow powder. 1H NMR (500 MHz, CDCl3) δ 8.49 (d, J = 9.29, 1H), 8.30 (d, J = 8.08, 1H), 8.18-8.15 (m, 3H), 8.12 (d, J = 9.28, 1H), 8.07-8.04 (m, 3H), 8.00 (t, J = 7.6, 1H), 7.61 (d, J = 8.65, 2H), 7.30 (d, J = 16.02, 1H), 6.95 (d, J = 8.69, 2H), 6.15 (s, 1H), 5.61 (q, J = 1.56, 1H), 4.37 (m, 4H), 4.03 (m, 2H), 2.46 (m, 2H), 1.97 (s, 3H), 1.87 (m, 4H). 13C NMR (125 MHz, CDCl3) δ 173.36, 167.30, 159.02, 136.10, 132.48, 131.74, 131.58, 131.17, 130.75, 130.74, 128.37, 128.13, 127.66, 127.60, 127.24, 126.28, 126.13, 125.32, 125.09, 123.69, 123.67, 123.29, 114.93, 67.58, 62.60, 62.23, 33.92, 28.80, 21.79, 18.48.

*

S-10

Figure S-7: 1H NMR spectrum of 11 (CDCl3, 500 MHz).

*

S-11

Figure S-8: 13C NMR spectrum of 11 (CDCl3, 125 MHz).

*

S-12

Synthesis of polymers

Scheme S-3: Synthetic route for the copolymer 13 Copolymer (13) TPT monomer (341 mg, 0.74 mmol), SP monomer (118 mg, 0.23 mmol), CTA (49.2 mg, 0.122 mmol) and AIBN (4 mg, 0.024 mmol) were dissolved in MMA (3.5 mL, 36.54 mmol) in the dark. DMF (5.3 mL) was added to the reaction mixture and it was sparged with N2 for 30 minutes. The polymerization was stirred at 80°C for 24 hours under N2. The reaction was cooled to room temperature and then precipitated into MeOH (150 mL). The polymer was filtered off and washed with MeOH (2 x 30 mL) and Et2O (2 x 30 mL) to yield 2.43 g of 13 as a light green solid. The percent incorporation of the monomers was found to be 6% TPT and 4% SP by 1H NMR.

Percent incorporation was calculated by calibrating the SP doublet labeled ‘b’ in Figure S-9 to the theoretical value of 4. The ratios of the actual over the theoretical integrations of TPT and MMA were calculated as shown below. The actual integration of the TPT aromatic hydrogens was determined by subtracting the theoretical integration of the SP aromatic hydrogens. The percent incorporations were calculated by dividing each ratio by the total of the two, as shown below. 𝑇𝑃𝑇𝑟𝑎𝑡𝑖𝑜 = !".$%&%'

%$= 1.41;𝑀𝑀𝐴𝑟𝑎𝑡𝑖𝑜 = $$.($

!= 22.09;%𝑇𝑃𝑇 = %.)%

%.)%*((.+,=

6%;%𝑀𝑀𝐴 = ((.+,%.)%*((.+,

= 90%;%𝑆𝑃 = 100 − (6 + 90) = 4%

SCNP (14) 13 (23.3 mg) was dissolved in MeCN (2.33 mL) in a foil wrapped vial. The polymer was allowed to completely dissolve and then the foil was removed. The vial was placed about 6 in. in front of a white CFL light with a cooling fan above it. The vial was irradiated without stirring for 1 hour and then immediate wrapped in foil. The mixture was concentrated in vacuo in the dark to yield the nanoparticle.

S-13

Figure S-9: 1H NMR spectrum of 13 (CDCl3, 400 MHz)

SP =O

OO

b

b

O

BF4

TPT =

1H NMR (CDCl3, 400 MHz)

a

Me

OO

Me

O O

SMe

OOSPTPT Me

CNOH

OC12H25S

S

13 a

b *

*

S-14

Figure S-10: SEC overlay of TPT-based polymer before and after crosslinking to form the SCNP (THF).

0.0

0.1

0.2

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0.5

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0.7

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0.9

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6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0

Rel

ativ

e In

tens

ity

Time (min)

CopolymerSCNP

Mn = 12.0 kDa Mw = 17.0 kDa Ð = 1.45 tR = 8.23 min

Mn = 14.0 kDa Mw = 19.0 kDa Ð = 1.35 tR = 8.26 min

S-15

Figure S-11: UV-Vis overlay of the copolymer before (red) and after crosslinking (blue) to form the SCNP (MeCN). The SCNP (secondary axis) was found to saturate the UV detector at similar concentrations (10 mg/mL), thus is more diluted in this measurement.

Scheme S-4: Synthetic route for homopolymers 14 and 15

Homopolymers (14, 15) Either the TPT (341 mg, 0.74 mmol) or SP (118 mg, 0.23 mmol) monomer was combined with CTA (49.2 mg, 0.122 mmol) and AIBN (4 mg, 0.024 mmol) and dissolved in MMA (3.5 mL, 36.54 mmol) in the dark. DMF (5.3 mL) was added to the reaction mixture and it was sparged with N2 for 30 minutes. The polymerization was stirred at 80 °C for 24 hours under N2. The reaction was cooled to room temperature and then precipitated into MeOH (150 mL). The polymer was filtered off and washed with MeOH (2 x 30 mL) and Et2O (2 x 30 mL) to yield the homopolymer as a yellow powder.

0

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0.6

0.7

0.8

0.9

1.0

280.0 310.0 340.0 370.0 400.0 430.0

Abs

orba

nce

Abs

orba

nce

Wavelength (nm)

S-16

Figure S-12: SEC of TPT-co-MMA (THF).

0.0

0.1

0.2

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0.5

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0.9

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Rel

ativ

e In

tens

ity

Time (min)

Mn = 15.2 kDa Mw = 17.9 kDa Ð = 1.17 tR = 8.3 min

S-17

Figure S-13: SEC overlay of SP-based polymer before (red) and after crosslinking (blue) to form the SCNP (THF).

[2+2] cyclodimerizations

Scheme S-5: General synthetic route for the dimerization of an alkene. Dimer The desired alkene (2 equiv., 0.1 mmol), and the SCNP stock solution (2 mol % TPT at 10 mg/mL) were added to a scintillation vial in the dark. Solid alkenes were added before the SCNP and liquid alkenes were added after. The vial was then sealed with electrical tape and sparged with a nitrogen needle and a vent needle for 10 minutes. The needles were removed, and the top of the vial was promptly covered with electrical tape. The vial was then placed between two 427nm Kessil lamps at 25% intensity and stirred for 24 hrs.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

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1.1

6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0

Rel

ativ

e In

tens

ity

Time (min)

Mn = 19.3 kDa Mw = 22.8 kDa Ð = 1.18 tR = 8.2 min

Mn = 18.3 kDa Mw = 21.5 kDa Ð = 1.02 tR = 8.2 min

S-18

Table S-1: Optimization table for the dimerization of trans-anethole.

427 nm Kessil lamp

2 mol% photocatalystMeCN (0.2 M)

25% light intensity, 24 h2 equiv.0.1 mmol

MeMe

MeO

Me

OMe

MeO

Deviations from Standard

None

427 nm Kessil PR160L LED

0.1 mol % SCNP

0.4 M

0.5 M

0.6 M

0.8 M

0.25 mol % SCNP, 0.8 M

0.33 mol % SCNP, 0.6 M

0.5 mol % SCNP, 0.4 M

48 h

50 % light intensity

50 % light intensity, 48 h

DCM

DMF

Yield

66 %

66 %

trace

71 %

28 %

30 %

32 %

5 %

8 %

16 %

42 %

15 %

29 %

14 %

5 %

S-19

16 66% yield. 1H NMR (500MHz, CDCl3) δ 7.05 (d, J = 6.67, 4H), 6.75 (d, J = 6.55, 4H), 3.69 (s, 6H), 2.73-2.71 (m, 2H), 1.75-1.73 (m, 2H), 1.11-1.09 (m, 6H).

Figure S-14: 1H NMR spectrum of 16 (CDCl3, 500 MHz)

*

S-20

17 26% yield. 1H NMR (400MHz, CDCl3) δ 7.10 (d, J =8.14, 4H), 6.79 (d, J =8.13, 4H), 3.74 (s, 6H), 3.40 (m, 2H), 2.42-2.41 (m, 2H), 1.87-1.85 (m, 2H).

Figure S-15: 1H NMR spectrum of 17 (CDCl3, 400 MHz)

*

S-21

18 49% yield. 1H NMR (500MHz, CDCl3) δ 6.93 (s, 2H), 6.44 (s, 2H), 3.85 (s, 6H), 3.83 (s, 6H), 3.67 (s, 6H), 3.24 (dd, J = 3.33, 2.37, 2H), 1.87 (dd, J = 1.74, 4.89, 2H), 1.16 (d, J = , 6H)

Figure S-16: 1H NMR spectrum of 18 (CDCl3, 500 MHz)

Control experiments The desired alkene (0.1 mmol), a photocatalyst (1 mol%), an electron relay (1 mol%), and acetonitrile (0.47 mL, 0.2 M) were added to a foil wrapped 20 mL scintillation vial. The vial was then sealed with electrical tape and sparged with a nitrogen needle and a vent needle for a half hour. The needles were removed and the top of the vial was promptly covered with electrical tape. The vial was then placed under 427nm Kessil lamps at 25% intensity and stirred overnight. After 24 hrs. an aliquot was taken with a needle and a 1 mL syringe. * If a polymer was used for the ER, it was crosslinked Cross [2+2] cycloaddition

Scheme S-6: Synthetic route for the cross-dimerization of trans-anethole with styrene.

*

S-22

21 The SNCP stock solution (2 mol% at 10 mg/mL), styrene (0.18 mL, 1.5 mmol), and trans-anethole (0.15 mL, 1.0 mmol), were added to a foil wrapped scintillation vial. The vial was then sealed with electrical tape and sparged with a nitrogen needle and a vent needle for 30 minutes. After sparging the top of the vial was also sealed with electrical tape. The vial was then placed under 427nm Kessil lamps at 25% intensity and stirred for 24 hrs. This afforded the desired product 21 in 44% yield. 1H NMR (500MHz, CDCl3) δ 7.33 (d, J = 8.5, 2H), 7.19 – 7.15 (m, 5H), 6.77-6.75 (m, 2H), 3.69 (s, 3H), 3.30 (q, J = 8.16, 1H), 2.86 (t, J = 9.51, 1H), 2.45-2.42 (dt, J = 10.16, 7.77, 1H), 1.75 (m, 1H), 1.61 (q, J = 10.14, 1H), 1.10 (d, J = 6.43, 3H) (ref: Yu, Y.; Fu, Y.; Zhong, F. Green Chem., 2018, 20, 1743-1747)

Figure S-17: 1H NMR spectrum of 21 (CDCl3, 500 MHz)

*

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