Visible-Light-Driven Anti-Markovnikov Hydrocarboxylation of Acrylates and Styrenes with CO ₂

Open AccessCCS ChemistryRESEARCH ARTICLE1 Jun 2021Visible-Light-Driven Anti-Markovnikov Hydrocarboxylation of Acrylates and Styrenes with CO2 He Huang†, Jian-Heng Ye†, Lei Zhu†, Chuan-Kun Ran, Meng Miao, Wei Wang, Hanjiao Chen, Wen-Jun Zhou, Yu Lan, Bo Da-Gang Huang† Key Laboratory Green Chemistry & Technology Ministry Education, College Chemistry, Analytical Testing Center, Sichuan University, Chengdu 610064 †H. Huang, J.-H. Ye, L. Zhu contributed equally to this work.Google Scholar More articles by author , Ye† Zhu† School Chemical Engineering, Chongqing 400030 Ran Google Miao Wang Chen Zhou Lan *Corresponding authors: E-mail Address: [email protected] Institute Catalysis, Zhengzhou 450001 https://doi.org/10.31635/ccschem.020.202000374 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd favoritesTrack Citations ShareFacebookTwitterLinked InEmail Light-driven carbon dioxide (CO2) capture utilization is one the most fundamental reactions in Nature. Herein, we report first visible-light-driven photocatalyst-free hydrocarboxylation alkenes CO2. Diverse acrylates styrenes, including challenging tri- tetrasubstituted ones, undergo anti-Markovnikov high selectivities generate valuable succinic acid derivatives 3-arylpropionic acids. In addition use stoichiometric aryl thiols, thiol catalysis also developed, representing organocatalytic The UV–vis measurements, NMR analyses, computational investigations support formation a novel charge-transfer complex (CTC) between thiolate acrylate/styrene. Further mechanistic studies density functional theory (DFT) calculations indicate that both alkene radical anions might be generated, illustrating unusual providing strategy for utilization. Download figure PowerPoint Introduction Photosynthesis nature. For more than century, chemists have been mimicking nature searching highly efficient visible-light photochemistry realize chemical transformations an environmentally friendly way.1 As diverse organic compounds cannot excited visible light, external photocatalysts are indispensable cases.2–5 Compared widely investigated photocatalysis, or electron donor acceptor (EDA) absence photocatalyst less although it economical sustainable industry.6 Notably, light-driven CTC thiols/disulfides has attracted great deal attention polymer chemistry.7–9 example, reported disulfides as donors acceptors (Figure 1b).9 While few examples CTCs thiolates (hetero)arenes reported,10–13 best our knowledge, acrylates/styrenes not reported. Figure 1 | (a) Selected derivatives. (b–d) Visible-light-driven acrylates/styrenes. CTC, complex; 4-PE-HE, 4-phenethyl Hantzsch ester. Carbon (CO2), well-known greenhouse gas, gained considerable ideal one-carbon building block due its abundance, low cost, sustainability.14–23 Hydrocarboxylations CO2, especially transition-metal-catalyzed hydrocarboxylations, represent strategies bioactive synthetically useful carboxylic acids.24 Recently, UV-light photocatalysis,16,25–27 photocatalysis emerged intriguing CO2.17,18,22,28–42 Iwasawa pioneered realizing Markovnikov regioselectivity via photoredox/Rh dual catalysis.27,41 Besides selectivity, König et al.35 realized styrenes regioselectivity26,43–45 photoredox/nickel catalysis. these cases, transition-metal catalysts indispensable. Moreover, proposed reaction reactive organometalic intermediates low-valent catalyst, which two-electron processes. contrast, still single-electron activation corresponding anion, selectivity hard control. CO2,46 demand provide pharmaceuticals 1a),47 chemistry industry,48 remains unresolved challenge, wondered whether could economical, efficient, selective way. We envisioned electron-rich electron-deficient form facilitate reduction anions, thus promoting 1c). recognized, however, such faced many challenges. thiol–ene reaction, oligmerization, and/or polymerization C–S bond competitively efficient.7,8,49 thiocarboxylation33 transesterification may occur, further complicating mixture. success under conditions, enabled acrylate/styrene 1d). Experimental Section methods To oven-dried Schlenk tube (10 mL) equipped magnetic stir bar added (0.2 mmol, 1.0 equiv nonliquid substrates). Then moved into glovebox charged NaOtBu (0.5 2.5 equiv). sealed, evacuated, backfilled three times. Subsequently, opened N-Methyl-2-pyrrolidinone (NMP) (2 added, followed thiophenol (0.4 2.0 equiv), tBuOH liquid substrates) syringe Once resulting mixture degassed using freeze-pump-thaw procedure (two times). sealed at atmospheric pressure (1 atm). stirred irradiated 30 W blue light-emitting diode (LED) lamp cm away, cooling fan keep temperature 25 °C region located center LED lamp) 24 h. diluted 3 mL EtOAc quenched 1.5 2 N HCl, then 5 min. extracted six times, combined phases concentrated vacuo. residue purified silica gel flash column chromatography (petroleum ether/EtOAc/AcOH 10/1/0.4%∼3/1/0.4%) give pure desired product. details found Supporting Information. Computational All carried out Gaussian 0950 series programs. DFT method ωB97XD51 standard 6–31+G(d) basis set used geometry optimizations. solvent effects considered universal solvation model based on solute (SMD)52. Harmonic vibrational frequency performed all stationary points confirm them local minima transition structures, derive thermochemical corrections enthalpies free energies. large 6–311+G(d,p) calculate single-point energies accurate energy information. Results Discussion At beginning research, hypothesized proton source sterically hindered thiols inhibit side reactions, thiocarboxylation reactions. After systematic screening (Table 1), methacrylate 1a proceeded presence easily available bulky thiol, 2,4,6-triisopropylthiophenol, well product 2a 73% yield (Entry 1). chemo- regioselectivities were excellent; only very yields 2a′ (8% yield) 2a″ (<5% obtained. Neither Markovnikov-type hydro- nor was observed. Control experiments confirmed essential roles base, (Entries 2–5). tBuOH, obtained much lower 6). Using iPrOH instead gave 7). 4-tert-butylthiophenol, resulted poorer chemoselectivity 8–10). Other bases solvents tested, but they worse results 11 12). Table Optimization Reaction Conditions Entry Alteration Yield/2a Yield/2a′ Yield/2a″ None 76% (73%) 8% <5% Without ArSH N.D. light 34% 4 33% Under N2 6 42% 6% 7 65% 12% 8 p-tBuC6H4SH 64% 24% 9 p-tBuC6H4SH, FeCl3 (5 mol %) Trace 5% 66% 10 9, equiv) 16% K2CO3 46% 21% 12 DMSO NMP conditions: mmol), 2,4,6-triisopropylthiophenol (ArSH, 0.4 mL), atm LED, RT, determined crude 1H CH2Br2 internal standard. Yield isolated provided parenthesis. DMSO, dimethyl sulfoxide; diode; N.D., detected; room temperature. With satisfactory conditions (Condition A: 1, 1) hand, aimed investigate scope 2). A diversity 2-methylacrylates bearing tertiary ( 1a– 1e), secondary 1f– 1h), primary 1i 1j) alkyl substituents ester moiety underwent regioselectivity. methyl, other kinds 1k– 1o), 1p– 1r), 1s) groups, groups 1t– 1w), tolerated α-position tert-butyl acrylates. Excellent observed 2-allylacrylate 1o. Furthermore, β-substituted products 2x– 2ba good yields. steric hindrance, 1ca 1da, moderate accompanied recovery starting material (in 28% 44% respectively) without any reduction, detected. some 1ea– 1ia) motifs, isoborneol, L-(–)-menthol, α-terpineol, 4-carvomenthenol, β-cholesterol, applicable transformation, acids Substrate styrenes. Condition B: h, C: (0.02 4-PE-HE (0.6 aThe diastereoselectivity (d.r.) values about 1∶1 NMR. b3 used. cd.r. = 3∶1. dd.r. 1.8∶1. eThe Z/E ratio 1∶1. fd.r. 5∶1. gd.r. > 19∶1, cis-isomer (see Information details). h3 3.5 used, 48 iGram scale. j2 p-tBuC6H4SNa NaOtBu, tBuOH. kThe (95∶5) 4p 4a ultra-performance (UPLC). temperature; 1a),35,43–45 slightly modified A), either electron-neutral 3a– 3c, 3i, 3m) electron-donating 3d, 3f, 3j) arene reacted smoothly afford heteroarenes 3g 3ba) well. electron-withdrawing CF3 group 3h) compatible 31% when employing p-tBuC6H4SNa. o-allyloxystyrene 3l 4l excellent chemoselectivity. 3-Chlorostyrene 3q provides 4q little dehalogenation (95∶5 4q: 4a). mono-, di-, trisubstituted arenes α-substitution suitable substrates protocol. 4ia, antidiabetic GPR40 agonist, generated 74% through 3ia. substrates, 3ma), 50% yield. gram-scale 3a went 78%. Interestingly, dihydrobenzothiazole replace generation 68% otherwise identical Given act main byproducts incorporated products, reductant. If successful, would However, significant challenges remained facile alkenes, thiocarboxylation, consume catalyst terminate catalytic cycle. competitive reductant difficult Therefore, strove Fortunately, (4-PE-HE)53 promote catalysis, 70% C), acrylates, those different moieties 1a, 1f, 1h, 1i), α-alkyl 1k, 1r, 1s), α-phenyl 1t), β-ethyl 1y) substitution, substrates. 1ha 1ia, transformation smoothly. mono- 3b, 3e, disubstituted 3r 3x) delivered successful application α-aryl 3ca– 3ea) α-methyl 3ja) realized. gain insights mechanism, tested various control 3). When 2,2,6,6-tetramethyl-1-piperinedinyloxy (TEMPO) mixture, detected 3a). “Radical clock” exclusive ring-opening 3b). These suggested intermediates. addition, reductive coupling 3a, 3aa, 3la (Figures 3c–3e). Cyclic voltammetry (CV) test demonstrated Electron paramagnetic resonance (EPR) spectroscopy supported radicals system 3f 3g). 13C-labeled 2a, sodium formate, oxalate, 13C-labeling 3h). formate oxalate 3i), reduced conditions. (a–i) Mechanistic studies. EPR, resonance; HRMS, high-resolution mass spectra; TEMPO, 2,2,6,6-tetramethyl-1-piperinedinyloxy. probe hypothesis conducted absorption spectra tests. slight bathochromic shift 4b). 4-(trifluoromethyl)styrene, 4c). seek evidence formation, 19F-NMR experiments, mixing certain amount 4-(trifluoromethyl)styrene increasing amounts distinctly downfield 4d), indicating increased donation from strongly (−2.66 V vs Ag/Ag+; see details) indicated measurements measurement 1a. (b) 3a. (c) 4-(trifluoromethyl)styrene. (d) Correlation relative concentration 19F-NMR. (e) HOMO −6.45 eV. (f) LUMO +0.86 (g) ESP surface singlet state CTC. (h) triplet DFT, theory; ESP, electrostatic potential; HOMO, highest occupied molecular orbital; LUMO, lowest unoccupied orbital. experimental evidence, acrylate ωB97XD/6–31+G(d) level theory. gap 7.31 eV 4e 4f) compared Figures S18a–S18d), arise orbital (HOMO) (LUMO) HOMO–LUMO explained potential (ESP) states showed take place 4g 4h). Although acceptor, thiolate, favored because higher (8.06 eV) (65.5 kcal/mol; S21 S23) thiolate–alkene (7.31 eV; 56.5 system. Based results, possible pathways 5a). Irradiation styrene anion (Path a) b) 8. Both same intermediate hydrogen atom transfer (HAT) produce carboxylate 10. Final protonation lead 4a. 4a, hydrothiolation 12, 9. (a–c) Proposed mechanism calculations. possibility two productive 5a, Paths b), did drive single (SET) process (−4.0 kcal/mol) (−9.7 respectively. This thermodynamically favorable 5b). spin distribution complexes calculated β-position, issue 5c). TS-1 afforded carboxylated barrier 11.6 kcal/mol, leading hydrocarboxylation. radical, leads (via TS-2), up 13.2 kcal/mol. 9.9 kcal/mol endergonic kinetically hydrothiolation. alternative TS-1-iso unfavorable (16.2 comparison selectivity. Starting distinct TS-4, 17.5 observed, inclined conduct HAT TS-3, 10.9 kcal/mol). process, dihygrobenzothiazole-involved case clarity Conclusion discovered acrylate/styrene, tests, investigations. acids, featuring regio- chemoselectivities. general practical substitution modes, ones. can transition-metal-free show pharmaceuticals, chemistry, industry, applications underway laboratory. available. Conflict Interest authors declare following competing financial interest: Chinese patent work pending number (201911022392.0). Acknowledgments Financial National Natural Science Foundation China (nos. 21822108, 21822303, 21801176, 21772129, 21772020), Fok Ying Tung Education (no. 161013), Program 2019YJ0379 20CXTD0112), Fundamental Research Funds Central Universities. References 1. Xuan J.; Xiao W.-J.Visible-Light Photoredox Catalysis.Angew. Chem. Int. Ed.2012, 51, 6828–6838. 2. Stephenson C. R. Yoon T.; MacMillan D. W. C.Visible Light Photocatalysis Organic Chemistry; Wiley-VCH, 2018. 3. Y.; Lu L.-Q.; D.-G.; C.-J.; W.-J.Visible photochemical synthesis China. Sci. 2019, 62, 24–57 4. Liu Q.; Wu L.-Z.Recent Advances Visible-Light-Driven Reactions.Natl. Rev.2017, 4, 359–380. 5. Marzo L.; Pagire S. K.; Reiser O.; B.Visible-Light Photocatalysis: Does It Make Difference Synthesis?Angew. Ed.2018, 57, 10034–10072. 6. Buzzetti Crisenza G. E. M.; Melchiorre P.Mechanistic Studies Photocatalysis.Angew. Ed.2019, 58, 3730–3747. 7. Dénès F.; Pichowicz Povie G.; Renaud P.Thiyl Radicals Synthesis.Chem. 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