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. File list (2) download file view on ChemRxiv Elacqua_dimerization_final.pdf (2.07 MiB) download file view on ChemRxiv Elacqua_Dimerization SI_final.pdf (2.27 MiB)
Single-chain polymer nanoparticles (SCNPs) are emerging as versatile catalytic platforms that provide excellent control over solubility. The confined nature of SCNPs can improve the rate of catalysis. While significant headway has been made in thermally-induced transition-metal catalysis with SCNPs, lightactivated SCNP catalysts have received little attention. We are developing triarylpyrylium tetrafluoroborate (TPT)-functionalized SCNPs as oxidative photocatalysts. Herein, we comprehensively study the impact of light source on both SCNP compaction and TPT absorbance through gel-permeation chromatography and UV/Vis spectroscopy. We observe that compaction is expedited using light sources that excite the photocatalyst (e.g., blue LEDs), which is attributed to the ability of TPT to dimerize sytrenics under similar photoredox conditions. The resultant metal-free SCNP photocatalysts enable the oxidation of benzyl alcohols in good yields. The SCNP is further investigated for the amidation of 4-bromobenzaldehyde, wherein it affords higher yields of the benzamide product compared to both small-molecule and unfolded polymer controls. We attribute the combined results to the colocalization of the TPT photoredox catalyst and pyrene electron relay within the SCNP, which likely aids in single-electron transfer processes. The scope of amidation reactions was also extended to other aryl aldehydes, wherein deactivated substrates afforded the highest yield of the desired amide.
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