Next Article in Journal
Promotional Effect of Manganese on Selective Catalytic Reduction of NO by CO in the Presence of Excess O2 over M@La–Fe/AC (M = Mn, Ce) Catalyst
Previous Article in Journal
Dry Hydrogen Production in a Tandem Critical Raw Material-Free Water Photoelectrolysis Cell Using a Hydrophobic Gas-Diffusion Backing Layer
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 10
Issue 11
10.3390/catal10111320
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Iron-Catalyzed Conjugate Addition of Aryl Iodides onto Activated Alkenes under Air in Water

by
Chung-Min Huang
†,
Wen-Sheng Peng
†,
Ling-Jun Liu
,
Chien-Chi Wu
and
Fu-Yu Tsai
*
Institute of Organic and Polymeric Materials, National Taipei University of Technology, 1, Sec. 3, Chung-Hsiao E. Rd., Taipei 10608, Taiwan
*
Author to whom correspondence should be addressed.
†
These authors contributed equally.
Catalysts 2020, 10(11), 1320; https://doi.org/10.3390/catal10111320
Submission received: 29 September 2020 / Revised: 11 November 2020 / Accepted: 12 November 2020 / Published: 13 November 2020
Browse Figures
Versions Notes

Abstract

:
The combination of commercially available FeCl3·6H2O with a water-soluble cationic 2,2′-bipyridyl catalytic system was found to enable the direct conjugate addition of aryl iodides onto activated alkenes, such as an α,β-unsaturated ester and a ketone, in a weakly acidic aqueous solution. This operationally simple protocol was carried out at 80 °C under air atmosphere in a potassium acetate-buffered aqueous solution for 12 h in the presence of Zn dust as a reductant to provide the desired 1,4-adducts in good yields.

Graphical Abstract

1. Introduction

Transition-metal-catalyzed conjugate addition onto α,β-unsaturated carbonyl compounds for the formation of C–C bonds is one of the most promising and powerful methods in organic synthesis [1]. Conventionally, pre-formed stoichiometric organometallic compounds, such as organoboron, organotin, organozinc, and organosilicon (which are usually prepared from alkyl/aryl halides), are required as the nucleophilic reagents to couple with activated olefins under Co [2], Ni [3,4,5,6,7], Cu [8,9,10], Ru [11], Rh [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40], Pd [41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63], and Ir [64,65] catalysis. Recently, Pd-based [66,67,68,69] and first transition series catalysts, such as Co [70,71,72,73,74,75,76,77], Ni [77,78,79,80], In/Cu [81], and Cu [82,83,84,85,86], for the conjugate addition of organic halides, triflates, or tosylates onto activated alkenes have been well-documented. The advantage of this protocol is that the pre-formed stoichiometric organometallic nucleophile is not required prior to the conjugate addition [87]. Typically, the transition-metal-catalyzed conjugate addition of organic halides onto activated olefins is conducted in hydrous organic solvents, where H2O is used to facilitate the protonolysis of the carbon–metal bond to afford the 1,4-adducts. There are only a few reports of these reactions performing in aqueous media [81,82,83,84,85,86]. Hence, the challenge remains to develop efficient conjugate addition reactions conducted in aqueous solutions to reduce the waste of organic solvents.
Based on the environmental and economic concerns, the use of iron—which is nontoxic and the cheapest transition metal—to catalyze 1,4-addition is highly desirable. Lipshutz reported that an Fe(II) salt can catalyze the reductive coupling of alkyl halides with either vinyl aromatics or heteroaromatics in an aqueous solution in the presence of a surfactant [88]. However, the iron-catalyzed conjugate addition of aryl halides onto activated olefins in water has not yet been explored. We previously found that the combination of commercially available FeCl3·6H2O with a water-soluble cationic 2,2′-bipyridyl ligand, L, as a catalytic system is able to catalyze the Sonogashira coupling of aryl iodides with terminal alkynes in water in the presence of excess Zn dust as a reductant [89]. Herein, we report that this iron catalytic system is capable of catalyzing the conjugate addition of aryl iodides onto activated alkenes in water under an air atmosphere by an operationally simple procedure (Scheme 1).

2. Results and Discussion

To examine our initial idea for iron-catalyzed conjugate addition, iodobenzene 1a (1 mmol) and n-butyl acrylate 2a (4 mmol) were added into an FeCl3·6H2O/L aqueous solution (10 mol% in 3 mL H2O) in the presence of Zn dust (3 mmol) as a reductant at 80 °C for 12 h; this produced butyl 3-phenylpropanoate, 3a, with a yield of only 22% (Table 1, Entry 1). We found that the FeCl3·6H2O/L aqueous solution was very acidic with a pH value of 1.8; hence, Zn may have reacted with the acid prior to reducing Fe(III). The addition of various amounts of potassium acetate (KOAc) to the aqueous phase led to the formation of a buffer solution with pH values between 5.0 and 5.8, which further increased the 1,4-adduct yields (Table 1, Entries 2–4). A more effective outcome was achieved when 2 mmol KOAc was added to the aqueous solution (Table 1, Entry 3). Other, stronger inorganic bases were also screened, but these basic aqueous solutions produced low yields of 3a, presumably due to the high hydroxide concentration that retarded the protonolysis of the C–Fe bond. This observation suggested that the pH control for this conjugate addition could be crucial (Table 1, Entries 5–7). Organic bases, such as Bu3N and iPr2NEt, are known to promote the Pd-catalyzed conjugate addition of aryl iodides onto α,β-unsaturated carbonyl compounds [66,67,68]; in our system, however, only a 47% yield of 3a was achieved when Bu3N was used (Table 1, Entry 8). A higher concentration of n-butyl acrylate, 2a, was necessary to provide higher product yields (Table 1, Entries 3, 9, and 10), which was also reported for the Ni-catalyzed reaction [78]. For the loading amount of Zn, we observed that 3 equivalents of Zn against 1a resulted in the highest product yield of 3a (Table 1, Entries 3 and 11–13). In addition, 99.99% pure FeCl3 was used to verify that this conjugate addition reaction was catalyzed by iron (Table 1, Entry 14) [90]. Without the addition of L, FeCl3·6H2O could not catalyze this conjugate addition, leading to the recovery of 86% of 1a (Table 1, Entry 15). Furthermore, the replacement of L by neutral 2,2′-bipyridine gave rise to an inferior yield of 3a (Table 1, Entry 16). These results revealed that the water-soluble ligand in the reaction was indispensable. Similarly, no 3a was formed when the catalytic system was left out of the reaction (Table 1, Entry 17). Finally, a scaled-up reaction was performed employing 5 mmol of 1a to give 3a in 75% yield (Table 1, Entry 18). Unfortunately, an aryl bromide, such as bromobenzene, did not participate in this 1,4 addition; hence, bromobenzene remained intact (Table 1, Entry 19).
Since the reaction conditions had been optimized, a variety of aryl iodides (1) were further employed to evaluate the conjugate addition with 2a under the conditions listed in Table 1, Entry 3, and the results are described in Table 2. A weakly electron-donating methyl group at the para position underwent a smooth reaction to produce 3b with a 74% yield (Table 2, Entry 1). However, this conjugate addition reaction did not proceed efficiently when a strong electron-donating group was added (Table 2, Entry 2). The low yield of 3c could be attributed to the methoxy group at the para position that decelerated the oxidative addition rate. Sterically congested aryl iodides, such as 1d and 1e, only slightly affected the reaction, producing 70% and 72% yields of 3d and 3e, respectively (Table 2, Entries 3 and 4). 3-Substituted aryl and 1-naphthyl iodides, 1f–1i, can also participate in this reaction, which produced the corresponding 1,4-adducts with yields between 75% and 79% (Table 2, Entries 5–8). For the electron-withdrawing groups 1j and 1k, moderate product yields were recorded (Table 2, Entries 9 and 10). Because Zn was prone to insertion into the carbon–iodine bond in the presence of aryl iodides bearing an electron-withdrawing group at the para position, the formation of ArZnI was dominant when 1j and 1k were applied. Though arylzinc iodides could be temporarily stabilized by a certain surfactant in water [91], in our cases with 1j and 1k, the swift protonolysis of the moisture-sensitive arylzinc iodides in weakly-acidic hot water resulted in the formation of the deiodinated by-products acetophenone and chlorobenzene, respectively [72,89]. The fast hydrolysis of ArZnX was further demonstrated using 3,5-dimethylphenylzinc chloride instead of using the iodide analogue, which gave rise to only m-xylene under the reaction conditions of Entry 7 in Table 2. The heteroaromatic 2-iodothiophene, 1l, failed to provide the desired conjugate adduct, resulting in the recovery of 1l (Table 2, Entry 11). A similar outcome was also observed in the Pd nanoparticle-catalyzed 1,4-addition reaction [68].
To further expand the substrate scope, other α,β-unsaturated carbonyl compounds, 2b and 2c, were added to this reaction (Table 3). The conjugate addition of aryl iodides onto alkenes proceeded smoothly, producing the desired products in yields of 70−84% (Table 3, Entries 1, 2, 4–11, and 13–18), except for the use of 4-iodoanisole 1c (Table 3, Entries 3 and 12). In contrast to 2-substituted aryl iodides, the steric hindrance on activated olefins inhibited the application of 2d and 2e in the conjugate addition reactions (Table 3, Entries 19 and 20).
To elucidate the reaction mechanism, the reaction conditions listed in Table 1, Entry 3 were performed in the presence of a 1 mmol radical scavenger, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl—TEMPO. We found that the presence of TEMPO in the reaction did not suppress the conjugate addition, which still produced 3a in an identical yield to that in Table 1, Entry 3; the radical pathway for this conjugate addition is therefore unlikely. In addition, >98% deuterium at the α-carbon to the product was observed when the reaction was conducted in D2O (see the Supporting Information for the 1H and 13C NMR spectra). This result implied that the Csp3–Fe bond was hydrolyzed by H2O to release the final product in the reaction. Following the above results, although the radical pathway cannot be completely ruled out, a similar mechanism to those in first-series transition-metal-catalyzed conjugate additions of aryl/alkyl halides onto α,β-unsaturated carbonyl compounds has been proposed [71,72,78]. As shown in Scheme 2, Fe(III) was first reduced by Zn dust, followed by the oxidative addition of an aryl iodide, to deliver aryl iron(III) intermediate A. The coordination of an activated olefin to the Fe(III) center and a subsequent migratory insertion provided intermediate B. The protonolysis of B by water afforded the conjugated addition product along with Fe(III). Then, reduction of Fe(III) by Zn regenerated Fe(I) for the next catalytic cycle.

3. Materials and Methods

3.1. General Methods

Aryl iodides, butyl acrylates, 2-cyclohexen-1-one, Bu3N, D2O, and FeCl3·6H2O were acquired from Acros Organics. KOAc, K2CO3, K3PO4, and KOH were purchased from SHOWA Chemical Co. Ltd (Tokyo, Japan). The cationic 2,2′-bipyridyl ligand (L) was prepared according to the known procedure [92,93]. NMR spectra were recorded in CDCl3 on a Bruker Biospin AG 300 NMR spectrometer (Bruker Co., Faellanden, Switzerland) at 25 °C, where the chemical shifts (δ in ppm) were established with respect to CHCl3, which was used as a reference (1H NMR: CHCl3 at 7.24; 13C NMR: CDCl3 at 77.0). High-resolution mass spectrometry (HRMS) was performed on a JEOL AccuTOF GCx-plus and SHIMADZU QP2020 at the Instrument Center Service, Ministry of Science and Technology of Taiwan. The spectral data of all conjugate adducts can be found in the Supporting Information.

3.2. Typical Procedure for the Conjugate Addition of Aryl Iodides onto Activated Olefins

A 20 mL cylinder reactor was charged with FeCl3·6H2O (0.1 mmol) and cationic 2,2′-bipyridyl ligand L (0.1 mmol in 3 mL of H2O). After stirring this solution at room temperature for 30 min, KOAc (2.0 mmol) was then added to the wine-red solution, which stirred for an additional 5 min. Aryl iodide (1.0 mmol), activated alkene (4.0 mmol), and Zn dust (3.0 mmol) were added in sequence, and the reaction mixture was then stirred at 80 °C under air atmosphere for 12 h. After cooling the reaction to room temperature, 3 N HCl (2 mL) was added into the aqueous solution and extracted with ethyl acetate (3 × 5 mL); the combined organic phase was then dried over MgSO4. The solvent was removed under reduced pressure, and the residue was purified by column chromatography on silica gel to give the desired product.

4. Conclusions

In conclusion, we developed an environmentally friendly method for the conjugate addition of aryl iodides onto activated alkenes catalyzed by a green catalytic system in water under an air atmosphere. Several activated olefins, such as an α,β-unsaturated ester and a ketone, can be applied to form 1,4-adducts in good-to-high yields. Nontoxic and cheap iron is used as the catalyst, and neither organometallic reagents nor organic solvents are required in this reaction, rendering this procedure sustainable. Further development of this green catalytic system for other reactions in water under ambient conditions is now underway in our laboratory.

Supplementary Materials

The following are available online at https://www.mdpi.com/2073-4344/10/11/1320/s1: the spectral data and copies of 1H- and 13C-NMR spectra of all conjugate addition products.

Author Contributions

C.-M.H., W.-S.P., L.-J.L., and F.-Y.T. conceived, designed, and executed the experiments and analyzed the data; W.-S.P. and C.-C.W. performed the NMR measurements; F.-Y.T. wrote the paper. All authors have read and agreed to the published version of the manuscript.

Funding

This research was financially supported by the Ministry of Science and Technology of Taiwan (MOST 108-2113-M-027-003).

Acknowledgments

We thank the Instrument Center Service at National Cheng Kung University, Ministry of Science and Technology of Taiwan for high-resolution mass spectrometry measurement.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Perlmutter, P. Conjugate Addition Reactions in Organic Synthesis; Pergamon Press: Oxford, UK, 1992. [Google Scholar]
  2. Chen, M.-H.; Mannathan, S.; Lin, P.-S.; Cheng, C.-H. Cobalt(II)-catalyzed 1,4-addition of organoboronic acids to activated alkenes: An application to highly cis-stereoselective synthesis of aminoindane carboxylic acid derivatives. Chem. Eur. J. 2012, 18, 14918–14922. [Google Scholar] [CrossRef] [PubMed]
  3. Shirakawa, E.; Yashuhara, Y.; Hayashi, T. Nickel-catalyzed conjugate addition of arylboron reagents to α,β-unsaturated carbonyl compounds with the aid of a catalytic amount of an alkyne. Chem. Lett. 2006, 35, 768–769. [Google Scholar] [CrossRef]
  4. Sieber, J.D.; Liu, S.; Morken, J.P. Catalytic conjugate addition of allyl groups to styryl-activated enones. J. Am. Chem. Soc. 2007, 129, 2214–2215. [Google Scholar] [CrossRef] [PubMed]
  5. Hirano, K.; Yorimitsu, H.; Oshima, K. Nickel-catalyzed 1,4-addition of trialkylboranes to α,β-unsaturated esters: Dramatic enhancement by addition of methanol. Org. Lett. 2007, 9, 1541–1544. [Google Scholar] [CrossRef] [PubMed]
  6. Meng, J.-J.; Gao, M.; Dong, M.; Wei, Y.-P.; Zhang, W.-Q. Catalyzation of 1,4-additions of arylboronic acids to α,β-unsaturated substrates using nickel(I) complexes. Tetrahedron Lett. 2014, 55, 2107–2109. [Google Scholar] [CrossRef]
  7. Chen, W.; Sun, L.; Huang, X.; Wang, J.; Peng, Y.; Song, G. Ligand-free nickel-catalysed 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds. Adv. Synth. Catal. 2015, 357, 1474–1482. [Google Scholar] [CrossRef]
  8. Takatsu, K.; Shintani, R.; Hayashi, T. Copper-catalyzed 1,4-addition of organoboronates to alkylidene cyanoacetates: Mechanistic insight and application to asymmetric catalysis. Angew. Chem. Int. Ed. 2011, 50, 5548–5552. [Google Scholar] [CrossRef]
  9. Yoshida, M.; Ohmiya, H.; Sawamura, M. Enantioselective conjugate addition of alkylboranes catalyzed by a copper−N-heterocyclic carbene complex. J. Am. Chem. Soc. 2012, 134, 11896–11899. [Google Scholar] [CrossRef]
  10. Liao, Y.-X.; Hu, Q.-S. CuCl/bipyridine-catalyzed addition reactions of arylboroxines with aldehydes, α,β-unsaturated ketones, and N-tosyl aldimines. J. Org. Chem. 2011, 76, 7602–7607. [Google Scholar] [CrossRef]
  11. Zhang, L.; Xie, X.; Peng, Z.; Fu, L.; Zhang, Z. Ru-catalyzed 1,4-addition of arylboronic acids to acrylic acid derivatives in the presence of phenols. Chem. Commun. 2013, 49, 8797–8799. [Google Scholar] [CrossRef]
  12. Hayashi, T.; Yamasaki, K. Rhodium-catalyzed asymmetric 1,4-addition and its related asymmetric reactions. Chem. Rev. 2003, 103, 2829–2844. [Google Scholar] [CrossRef] [PubMed]
  13. Zhao, G.-Z.; Foster, D.; Sipos, G.; Gao, P.; Skelton, B.W.; Sobolev, A.N.; Dorta, R. Electronic and steric tuning of an atropisomeric disulfoxide ligand motif and its use in the Rh(I)-catalyzed addition reactions of boronic acids to a wide range of acceptors. J. Org. Chem. 2018, 83, 9741–9755. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  14. Kamikawa, K.; Tseng, Y.-Y.; Jian, J.-H.; Takahashi, T.; Ogasawara, M. Planar-chiral phosphine-olefin ligands exploiting a (cyclopentadienyl)manganese(I) scaffold to achieve high robustness and high enantioselectivity. J. Am. Chem. Soc. 2017, 139, 1545–1553. [Google Scholar] [CrossRef] [PubMed]
  15. Lee, A.; Kim, H. Chiral bicyclic bridgehead phosphoramidite (briphos) ligands for asymmetric rhodium-catalyzed 1,2- and 1,4-addition. J. Org. Chem. 2016, 81, 3520–3527. [Google Scholar] [CrossRef]
  16. Ogasawara, M.; Tseng, Y.-Y.; Arae, S.; Morita, T.; Nakaya, T.; Wu, W.-Y.; Takahashi, T.; Kamikawa, K. Phosphine−olefin ligands based on a planar-chiral (π-arene)chromium scaffold: Design, synthesis, and application in asymmetric catalysis. J. Am. Chem. Soc. 2014, 136, 9377–9384. [Google Scholar] [CrossRef]
  17. Korenaga, T.; Ko, A.; Shimada, K. Low-temperature Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds. J. Org. Chem. 2013, 78, 9975–9980. [Google Scholar] [CrossRef]
  18. Liu, C.-C.; Janmanchi, D.; Chen, C.-C.; Wu, H.-L. Expanding the C1-symmetric bicyclo[2.2.1]heptadiene ligand family: Highly enantioselective synthesis of cyclic β-aryl-substituted carbonyl compounds. Eur. J. Org. Chem. 2012, 2012, 2503–2507. [Google Scholar] [CrossRef]
  19. Thaler, T.; Guo, L.-N.; Steib, A.K.; Raducan, M.; Karaghiosoff, K.; Mayer, P.; Knochel, P. Sulfoxide-alkene hybrids: A new class of chiral ligands for the Hayashi-Miyaura reaction. Org. Lett. 2011, 13, 3182–3185. [Google Scholar] [CrossRef]
  20. Xue, F.; Li, X.; Wan, B. A class of benzene backbone-based olefin-sulfoxide ligands for Rh-catalyzed enantioselective addition of arylboronic acids to enones. J. Org. Chem. 2011, 76, 7256–7262. [Google Scholar] [CrossRef]
  21. Berhal, F.; Wu, Z.; Genet, J.-P.; Ayad, T.; Ratovelomanana-Vidal, V. Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated ketones with DIFLUORPHOS and SYNPHOS analogues. J. Org. Chem. 2011, 76, 6320–6326. [Google Scholar] [CrossRef]
  22. Le Boucher d’Herouville, F.; Millet, A.; Scalone, M.; Michelet, V. Room-temperature Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to maleimides and enones in the presence of CF3-substituted MeOBIPHEP analogues. J. Org. Chem. 2011, 76, 6925–6930. [Google Scholar] [CrossRef] [PubMed]
  23. Duan, W.-L.; Iwamura, H.; Shintani, R.; Hayashi, T. Chiral phosphine-olefin ligands in the rhodium-catalyzed asymmetric 1,4-addition reactions. J. Am. Chem. Soc. 2007, 129, 2130–2138. [Google Scholar] [CrossRef] [PubMed]
  24. Shintani, R.; Yamagami, T.; Kimura, T.; Hayashi, T. Asymmetric synthesis of 2-aryl-2,3-dihydro-4-quinolones by rhodium-catalyzed 1,4-addition of arylzinc reagents in the presence of chlorotrimethylsilane. Org. Lett. 2005, 7, 5317–5319. [Google Scholar] [CrossRef]
  25. Chen, G.; Tokunaga, N.; Hayashi, T. Rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to coumarins: Asymmetric synthesis of (R)-tolterodine. Org. Lett. 2005, 7, 2285–2288. [Google Scholar] [CrossRef] [PubMed]
  26. Shintani, R.; Tokunaga, N.; Doi, H.; Hayashi, T. A new entry of nucleophiles in rhodium-catalyzed asymmetric 1,4-addition reactions: Addition of organozinc reagents for the synthesis of 2-aryl-4-piperidones. J. Am. Chem. Soc. 2004, 126, 6240–6241. [Google Scholar] [CrossRef] [PubMed]
  27. Oi, S.; Moro, M.; Ito, H.; Honma, Y.; Miyano, S. Rhodium-catalyzed conjugate addition of aryl- and alkenyl-stannanes to α,β-unsaturated carbonyl compounds. Tetrahedron 2002, 58, 91–97. [Google Scholar] [CrossRef]
  28. Oi, S.; Honma, Y.; Inoue, Y. Conjugate addition of organosiloxanes to α,β-unsaturated carbonyl compounds catalyzed by a cationic rhodium complex. Org. Lett. 2002, 4, 667–669. [Google Scholar] [CrossRef] [PubMed]
  29. Mori, A.; Danda, Y.; Fujii, T.; Hirabayashi, K.; Osakada, K. Hydroxorhodium complex-catalyzed carbon-carbon bond-forming reactions of silanediols with α,β-unsaturated carbonyl compounds. Mizoroki-Heck-type reaction vs conjugate addition. J. Am. Chem. Soc. 2001, 123, 10774–10775. [Google Scholar] [CrossRef]
  30. Takaya, Y.; Ogasawara, M.; Hayashi, T.; Sakai, M.; Miyaura, N. Rhodium-catalyzed asymmetric 1,4-addition of aryl- and alkenylboronic acids to enones. J. Am. Chem. Soc. 1998, 120, 5579–5580. [Google Scholar] [CrossRef]
  31. Ruiz-Botella, S.; Peris, E. Immobilization of pyrene-adorned N-heterocyclic carbene complexes of rhodium (I) on reduced graphene oxide and study of catalytic activity. ChemCatChem 2018, 10, 1874–1881. [Google Scholar] [CrossRef]
  32. Mühlhäuser, T.; Savin, A.; Frey, W.; Baro, A.; Schneider, A.J.; Döteberg, H.-G.; Bauer, F.; Köhn, A.; Laschat, S. Role of regioisomeric bicyclo[3.3.0]octa-2,5-diene ligands in Rh catalysis: Synthesis, structural analysis, theoretical study, and application in asymmetric 1,2- and 1,4-additions. J. Org. Chem. 2017, 82, 13468–13480. [Google Scholar] [CrossRef] [PubMed]
  33. Melcher, M.-C.; da Silva, B.R.A.; Ivšić, T.; Strand, D. Chiral discrimination in rhodium(I) catalysis by 2,5-disubstituted 1,3a,4,6a-tetrahydropenatalene ligands–more than just a twist of the Olefins? ACS Omega 2018, 3, 3622–3630. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  34. Ramasamy, B.; Prakasham, A.P.; Gangwar, M.K.; Ghosh, P. 1,4-Conjugate addition of aryl boronic acids on cyclohexenone as catalyzed by rhodium(I) complexes of C2-symmetric bioxazoline fused N-heterocyclic carbenes. ChemistrySelect 2019, 4, 8526–8533. [Google Scholar] [CrossRef]
  35. Motokura, K.; Hashiguchi, K.; Maeda, K.; Nambo, M.; Manaka, Y.; Chun, W.-J. Rh-catalyzed 1,4-addition reactions of arylboronic acids accelerated by co-immobilized tertiary amine in silica mesopores. Mol. Catal. 2019, 472, 1–9. [Google Scholar] [CrossRef]
  36. Borrego, L.G.; Recio, R.; Álvarez, E.; Sánchez-Coronilla, A.; Khiar, N.; Fernández, I. Steric tuning of sulfinamide/sulfoxides as chiral ligands with C1, pseudo-meso, and pseudo-C2 symmetries: Application in rhodium(I)-mediated arylation. Org. Lett. 2019, 21, 6513–6518. [Google Scholar] [CrossRef]
  37. Fan, C.; Wu, Q.; Zhu, C.; Wu, X.; Li, Y.; Luo, Y.; He, J.-B. Enantioselective conjugate addition of aryl halides and triflates to electron-deficient olefins via nickel- and rhodium-catalyzed sequential relay reactions. Org. Lett. 2019, 21, 8888–8892. [Google Scholar] [CrossRef]
  38. Pecchioli, T.; Christmann, M. Synthesis of highly enantioenriched propelladienes and their application as ligands in asymmetric Rh-catalyzed 1,4-additions. Org. Lett. 2018, 20, 5256–5259. [Google Scholar] [CrossRef]
  39. Nikol, A.; Zhang, Z.; Chelouan, A.; Falivene, L.; Cavallo, L.; Herrera, A.; Heinemann, F.W.; Escalona, A.; Frieß, S.; Grasruck, A.; et al. Tricyclic sulfoxide-alkene hybrid ligands for chiral Rh(I) complexes: The “matched” diastereomer catalyzes asymmetric C–C bond formations. Organometallics 2020, 39, 1348–1359. [Google Scholar] [CrossRef] [Green Version]
  40. Kirchhof, M.; Gugeler, K.; Fischer, F.R.; Nowakowski, M.; Bauer, A.; Alvarez-Barcia, S.; Abitaev, K.; Schnierle, M.; Qawasmi, Y.; Frey, W.; et al. Experimental and theoretical Sstudy on the role of monomeric vs dimeric rhodium oxazolidinone norbornadiene complexes in catalytic asymmetric 1,2- and 1,4-additions. Organometallics 2020, 39, 3131–3145. [Google Scholar] [CrossRef]
  41. Hamasaka, G.; Muto, T.; Andoh, Y.; Fujimoto, K.; Kato, K.; Takata, M.; Okazaki, S.; Uozumi, Y. Detailed structural analysis of a self-assembled vesicular amphiphilic NCN-pincer palladium complex by using wide-angle X-ray scattering and molecular dynamics calculations. Chem. Eur. J. 2017, 23, 1291–1298. [Google Scholar] [CrossRef]
  42. Tamura, M.; Ogata, H.; Ishida, Y.; Takahashi, Y. Design and synthesis of chiral 1,10-phenanthroline ligand, and application in palladium catalyzed asymmetric 1,4-addition reactions. Tetrahedron Lett. 2017, 58, 3808–3813. [Google Scholar] [CrossRef]
  43. de Gracia Retamosa, M.; Álvarez-Casao, Y.; Matador, E.; Gómez, Á.; Monge, D.; Fernández, R.; Lassaletta, J.M. Pyridine-hydrazone ligands in asymmetric palladium-catalyzed 1,4- and 1,6-additions of arylboronic acids to cyclic (di)enones. Adv. Synth. Catal. 2019, 361, 176–184. [Google Scholar] [CrossRef]
  44. Shimizu, M.; Yamamoto, T. 9-(Diphenylphosphino)anthracene-based phosphapalladacycle catalyzed conjugate addition of arylboronic acids to electron-deficient alkenes. Tetrahedron Lett. 2020, 61, 152257. [Google Scholar] [CrossRef]
  45. Gerten, A.L.; Stanley, L.M. Palladium-catalyzed conjugate addition of arylboronic acids to 2-substituted chromones in aqueous media. Tetrahedron Lett. 2016, 57, 5460–5463. [Google Scholar] [CrossRef]
  46. Shockley, S.E.; Holder, J.C.; Stoltz, B.M. Palladium-catalyzed asymmetric conjugate addition of arylboronic acids to α,β-unsaturated cyclic electrophiles. Org. Process Res. Dev. 2015, 19, 974–981. [Google Scholar] [CrossRef] [Green Version]
  47. Lan, Y.; Houk, K.N. Mechanism of the palladium-catalyzed addition of arylboronic acids to enones: A computational study. J. Org. Chem. 2011, 76, 4905–4909. [Google Scholar] [CrossRef]
  48. Tomás-Mendivil, E.; Díez, J.; Cadierno, V. Conjugate addition of arylboronic acids to α,β-unsaturated carbonyl compounds in aqueous medium using Pd(II) complexes with dihydroxy-2,2’-bipyridine ligands: Homogeneous or heterogeneous nano-catalysis? Catal. Sci. Technol. 2011, 1, 1605–1615. [Google Scholar] [CrossRef]
  49. Huang, S.-H.; Wu, T.-M.; Tsai, F.-Y. pH-dependent conjugate addition of arylboronic acids to α,β-unsaturated enones catalyzed by a reusable palladium(II)/cationic 2,2’-bipyridyl system in water under air. Appl. Organometal. Chem. 2010, 24, 619–624. [Google Scholar] [CrossRef]
  50. Nishikata, T.; Kiyomura, S.; Yamamoto, Y.; Miyaura, N. Asymmetric 1,4-addition of arylboronic acid to α,β-unsaturated esters catalyzed by dicationic palladium(II)-chiraphos complex for short-step synthesis of SmithKline Beecham’s endothelin receptor antagonist. Synlett 2008, 2008, 2487–2488. [Google Scholar] [CrossRef]
  51. Nishikata, T.; Yamamoto, Y.; Miyaura, N. Palladium(II)-catalyzed 1,4-addition of arylboronic acids to β-arylenals for enantioselective syntheses of 3,3-diarylalkanals: A short synthesis of (+)-(R)-CDP 840. Tetrahedron Lett. 2007, 48, 4007–4010. [Google Scholar] [CrossRef] [Green Version]
  52. He, P.; Lu, Y.; Dong, C.-G.; Hu, Q.-S. Anionic four-electron donor-based palladacycles as catalysts for addition reactions of arylboronic acids with α,β-unsaturated ketones, aldehydes, and α-ketoesters. Org. Lett. 2007, 9, 343–346. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  53. Gini, F.; Hessen, B.; Feringa, B.L.; Minnaard, A.J. Enantioselective palladium-catalysed conjugate addition of arylsiloxanes. Chem. Commun. 2007, 710–712. [Google Scholar] [CrossRef] [PubMed]
  54. Nishikata, T.; Yamamoto, Y.; Miyaura, N. Palladium(II)-catalyzed 1,4-addition of arylboronic acids to β-arylenones enantioselective synthesis of 4-aryl-4H-chromenes. Adv. Synth. Catal. 2007, 349, 1759–1764. [Google Scholar] [CrossRef]
  55. Yamamoto, T.; Iizuka, M.; Ohta, T.; Ito, Y. Palladium catalyzed conjugate 1,4-addition of organoboronic acids to α,β-unsaturated ketones. Chem. Lett. 2006, 35, 198–199. [Google Scholar] [CrossRef]
  56. Gini, F.; Hessen, B.; Minnaard, A.J. Palladium-catalyzed enantioselective conjugate addition of arylboronic acids. Org. Lett. 2005, 7, 5309–5312. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  57. Lu, X.; Lin, S. Pd(II)-bipyridine catalyzed conjugate addition of arylboronic acid to a,β-unsaturated carbonyl compounds. J. Org. Chem. 2005, 70, 9651–9653. [Google Scholar] [CrossRef] [PubMed]
  58. Nishikata, T.; Yamamoto, Y.; Miyaura, N. Asymmetric 1,4-addition of potassium aryltrifluoroborates [ArBF3]K to enones catalyzed by dicationic palladium(II) complexes. Chem. Lett. 2005, 34, 720–721. [Google Scholar] [CrossRef]
  59. Nishikata, T.; Yamamoto, Y.; Miyaura, N. 1,4-Addition of arylboronic acids and arylsiloxanes to α,β-unsaturated carbonyl compounds via transmetalation to dicationic palladium(II) complexes. Organometallics 2004, 23, 4317–4324. [Google Scholar] [CrossRef]
  60. Nishikata, T.; Yamamoto, Y.; Miyaura, N. Conjugate addition of aryl boronic acids to enones catalyzed by cationic palladium(II)–phosphane complexes. Angew. Chem. Int. Ed. 2003, 42, 2768–2770. [Google Scholar] [CrossRef]
  61. Ohe, T.; Wakita, T.; Motofusa, S.-I.; Cho, C.-S.; Ohe, K.; Uemura, S. Palladium(II)-catalyzed Michael-type addition reactions using aryltin compounds. Bull. Chem. Soc. Jpn. 2000, 73, 2149–2155. [Google Scholar] [CrossRef]
  62. Denmark, S.E.; Amishiro, N. Palladium-catalyzed conjugate addition of organosiloxanes to α,β-unsaturated carbonyl compounds and nitroalkenes. J. Org. Chem. 2003, 68, 6997–7003. [Google Scholar] [CrossRef] [PubMed]
  63. Nishikata, T.; Yamamoto, Y.; Miyaura, N. 1,4-Addition of arylsiloxanes to enones catalyzed by dicationic palladium(II) complexes in aqueous media. Chem. Lett. 2003, 32, 752–753. [Google Scholar] [CrossRef]
  64. Koike, T.; Du, X.; Sanada, T.; Danda, Y.; Mori, A. Iridium-catalyzed Mizoroki-Heck-type reaction of organosilicon reagents. Angew. Chem. Int. Ed. 2003, 42, 89–92. [Google Scholar] [CrossRef] [PubMed]
  65. Fei, F.; Lu, T.; Yang, C.-F.; Chen, X.-T.; Xue, Z.-L. Synthesis, structures, and catalytic properties of dinuclear iridium(I) complexes with a hexadentate macrocyclic diamine tetracarbene ligand. Eur. J. Inorg. Chem. 2018, 2018, 1595–1602. [Google Scholar] [CrossRef]
  66. Gottumukkala, A.L.; de Vries, J.G.; Minnaard, A.J. Pd–NHC catalyzed conjugate addition versus the Mizoroki–Heck reaction. Chem. Eur. J. 2011, 17, 3091–3095. [Google Scholar] [CrossRef] [Green Version]
  67. Mannathan, S.; Raoufmoghaddam, S.; Reek, J.N.H.; de Vries, J.G.; Minnaard, A.J. Palladium(II) acetate catalyzed reductive Heck reaction of enones; a practical approach. ChemCatChem 2015, 7, 3923–3927. [Google Scholar] [CrossRef]
  68. Parveen, N.; Saha, R.; Sekar, G. Stable and reusable palladium nanoparticles-catalyzed conjugate addition of aryl iodides to enones: Route to reductive Heck products. Adv. Synth. Catal. 2017, 359, 3741–3751. [Google Scholar] [CrossRef]
  69. Yang, W.; Ling, B.; Hu, B.; Yin, H.; Mao, J.; Walsh, P.J. Synergistic N-heterocyclic carbene/palladium-catalyzed umpolung 1,4-addition of aryl iodides to enals. Angew. Chem. Int. Ed. 2020, 59, 161–166. [Google Scholar] [CrossRef] [Green Version]
  70. Gomes, P.; Gosmini, C.; Nédélec, J.-Y.; Périchon, J. Cobalt bromide as catalyst in electrochemical addition of aryl halides onto activated olefins. Tetrahedron Lett. 2000, 41, 3385–3388. [Google Scholar] [CrossRef]
  71. Shukla, P.; Hsu, Y.-C.; Cheng, C.-H. Cobalt-catalyzed reductive coupling of saturated alkyl halides with activated alkenes. J. Org. Chem. 2006, 71, 655–658. [Google Scholar] [CrossRef]
  72. Amatore, M.; Gosmini, C.; Périchon, J. CoBr2(Bpy): An efficient catalyst for the direct conjugate addition of aryl halides or triflates onto activated olefins. J. Org. Chem. 2006, 71, 6130–6134. [Google Scholar] [CrossRef] [PubMed]
  73. Hsieh, J.-C.; Chu, Y.-H.; Muralirajan, K.; Cheng, C.-H. A simple route to 1,4-addition reactions by Co-catalyzed reductive coupling of organic tosylates and triflates with activated alkenes. Chem. Commun. 2017, 53, 11584–11587. [Google Scholar] [CrossRef] [PubMed]
  74. Aizawa, S.-I.; Fukumoto, K.; Kawamoto, T. Effect of phosphine and phosphine sulfide ligands on the cobalt-catalyzed reductive coupling of 2-iodobutane with n-butyl acrylate. Polyhedron 2013, 62, 37–41. [Google Scholar] [CrossRef]
  75. Lu, S.; Jin, T.; Bao, M.; Yamamoto, Y. Cobalt-catalyzed hydroalkylation of [60] fullerene with active alkyl bromides: Selective synthesis of monoalkylated fullerenes. J. Am. Chem. Soc. 2011, 133, 12842–12848. [Google Scholar] [CrossRef]
  76. Amatore, M.; Gosmini, C. Direct cobalt-catalyzed conjugate addition of functionalized aryl halides and triflates: A new strategy for the conjugate addition onto methyl vinyl ketone. Synlett 2009, 2009, 1073–1076. [Google Scholar] [CrossRef]
  77. Qian, Q.; Zang, Z.; Chen, Y.; Tong, W.; Gong, H. Nickel and cobalt-catalyzed coupling of alkyl halides with alkenes via Heck reactions and radical conjugate addition. Mini-Rev. Med. Chem. 2013, 13, 802–813. [Google Scholar] [CrossRef] [PubMed]
  78. Shukla, P.; Sharma, A.; Pallavi, B.; Cheng, C.-H. Nickel-catalyzed reductive Heck type coupling of saturated alkyl halides with acrylates and oxabenzonorbornadiene. Tetrahedron 2015, 71, 2260–2266. [Google Scholar] [CrossRef]
  79. Shrestha, R.; Weix, D.J. Reductive conjugate addition of haloalkanes to enones to form silyl Enol ethers. Org. Lett. 2011, 13, 2766–2769. [Google Scholar] [CrossRef]
  80. Shrestha, R.; Dorn, S.C.M.; Weix, D.J. Nickel-catalyzed reductive conjugate addition to enones via allylnickel intermediates. J. Am. Chem. Soc. 2013, 135, 751–762. [Google Scholar] [CrossRef] [Green Version]
  81. Shen, Z.-L.; Cheong, H.-L.; Loh, T.-P. Indium/copper-mediated conjugate addition of unactivated alkyl iodides to α,β-unsaturated carbonyl compounds in water. Tetrahedron Lett. 2009, 50, 1051–1054. [Google Scholar] [CrossRef]
  82. Fleming, F.F.; Gudipati, S. Alkenenitriles: Zn−Cu promoted conjugate additions of alkyl iodides in water. Org. Lett. 2006, 8, 1557–1559. [Google Scholar] [CrossRef] [PubMed]
  83. Zhou, F.; Hu, X.; Zhang, W.; Li, C.-J. Direct conjugate additions using aryl and alkyl organic halides in air and water. Org. Chem. Front. 2018, 5, 3579–3584. [Google Scholar] [CrossRef]
  84. Zhou, F.; Hu, X.; Zhang, W.; Li, C.-J. Copper-catalyzed radical reductive arylation of styrenes with aryl iodides mediated by zinc in water. J. Org. Chem. 2018, 83, 7416–7422. [Google Scholar] [CrossRef]
  85. Lipshutz, B.H.; Huang, S.; Leong, W.W.Y.; Zhong, G.; Isley, N.A. C−C bond formation via copper-catalyzed conjugate addition reactions to enones in water at room temperature. J. Am. Chem. Soc. 2012, 134, 19985–19988. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  86. Fleming, F.F.; Gudipati, S.; Aitken, J.A. Alkenenitriles: Conjugate additions of alkyl iodides with a silica-supported zinc-copper matrix in water. J. Org. Chem. 2007, 72, 6961–6969. [Google Scholar] [CrossRef]
  87. Streuff, J.; Gansäuer, A. Metal-catalyzed β-functionalization of Michael acceptors through reductive radical addition reactions. Angew. Chem. Int. Ed. 2015, 54, 14232–14242. [Google Scholar] [CrossRef]
  88. Pang, H.; Wang, Y.; Gallou, F.; Lipshutz, B.H. Fe-catalyzed reductive couplings of terminal (hetero)aryl alkenes and alkyl halides under aqueous micellar conditions. J. Am. Chem. Soc. 2019, 141, 17117–17124. [Google Scholar] [CrossRef]
  89. Hung, T.-T.; Huang, C.-M.; Tsai, F.-Y. Sonogashira–Hagihara coupling towards diaryl alkynes catalyzed by FeCl3·6H2O/cationic 2,2’-bipyridyl. ChemCatChem 2012, 4, 540–545. [Google Scholar] [CrossRef]
  90. Buchwald, S.L.; Bolm, C. On the role of metal contaminants in catalyses with FeCl3. Angew. Chem. Int. Ed. 2009, 48, 5586–5587. [Google Scholar] [CrossRef] [Green Version]
  91. Zhou, F.; Li, C.-J. The Barbier-Grignard-type arylation of aldehydes using unactivated aryl iodides in water. Nat. Commun. 2014, 5, 4254. [Google Scholar] [CrossRef] [Green Version]
  92. Wu, W.-Y.; Chen, S.-N.; Tsai, F.-Y. Recyclable and highly active cationic 2,2’-bipyridyl palladium(II) catalyst for Suzuki cross-coupling reaction in water. Tetrahedron Lett. 2006, 47, 9267–9270. [Google Scholar] [CrossRef]
  93. Chen, S.-N.; Wu, W.-Y.; Tsai, F.-Y. Hiyama reaction of aryl bromides with arylsiloxanes catalyzed by a reusable palladium(II)/cationic bipyridyl system in water. Tetrahedron 2008, 64, 8164–8168. [Google Scholar] [CrossRef]
Catalysts 10 01320 sch001 550
Scheme 1. Iron-catalyzed conjugate addition of aryl iodides onto activated alkenes.
Scheme 1. Iron-catalyzed conjugate addition of aryl iodides onto activated alkenes.
Catalysts 10 01320 sch001
Catalysts 10 01320 sch002 550
Scheme 2. Proposed mechanism for the conjugated addition.
Scheme 2. Proposed mechanism for the conjugated addition.
Catalysts 10 01320 sch002
Table
Table 1. Iron-catalyzed conjugate addition of iodobenzene (1a) onto n-butyl acrylate (2a) a.
Table 1. Iron-catalyzed conjugate addition of iodobenzene (1a) onto n-butyl acrylate (2a) a.
Entry2a (mmol)Zn (mmol)Base (mmol)pHYield (%) b
143--1.822
243KOAc (1)5.074
343KOAc (2)5.585
443KOAc (3)5.880
543K2CO3 (2)11.540
643K3PO4 (2)13.535
743KOH (2)15.423
843Bu3N (2)6.847
933KOAc (2) 77
1023KOAc (2) 52
1142.5KOAc (2) 74
1242KOAc (2) 61
1340KOAc (2) 0
14 c43KOAc (2) 86
15 d43KOAc (2) 0
16 e43KOAc (2) 12
17 f43KOAc (2) 0
18 g2015KOAc (10) 75
19 h43KOAc (2) 0
a Reaction conditions: 1a (1 mmol), 2a, Zn, base, FeCl3·6H2O/L (10 mol%), and H2O (3 mL) at 80 °C for 12 h. b Isolated yields. c 99.99% pure FeCl3 was used. d In the absence of ligand L. e Neutral 2,2′-bipyridine was used as the ligand. f In the absence of FeCl3·6H2O/L. g 5 mmol of 1a was used. h Iodobenzene 1a was replaced by bromobenzene.
Table
Table 2. Iron-catalyzed conjugate addition of aryl iodides (1) onto n-butyl acrylate (2a) a.
Table 2. Iron-catalyzed conjugate addition of aryl iodides (1) onto n-butyl acrylate (2a) a.
EntryAryl IodideProductYield (%) b
1 Catalysts 10 01320 i0011b Catalysts 10 01320 i0023b74
2 Catalysts 10 01320 i0031c Catalysts 10 01320 i0043c44
3 Catalysts 10 01320 i0051d Catalysts 10 01320 i0063d70
4 Catalysts 10 01320 i0071e Catalysts 10 01320 i0083e72
5 Catalysts 10 01320 i0091f Catalysts 10 01320 i0103f75
6 Catalysts 10 01320 i0111g Catalysts 10 01320 i0123g79
7 Catalysts 10 01320 i0131h Catalysts 10 01320 i0143h78
8 Catalysts 10 01320 i0151i Catalysts 10 01320 i0163i75
9 Catalysts 10 01320 i0171j Catalysts 10 01320 i0183j40
10 Catalysts 10 01320 i0191k Catalysts 10 01320 i0203k52
11 Catalysts 10 01320 i0211l Catalysts 10 01320 i0223l 0
a Reaction conditions: 1 (1 mmol), 2a (4 mmol), Zn (3 mmol), KOAc (2 mmol), FeCl3·6H2O/L (10 mol%), and H2O (3 mL) at 80 °C for 12 h. b Isolated yields.
Table
Table 3. Iron-catalyzed conjugate addition of aryl iodides (1) onto activated alkenes (2) a.
Table 3. Iron-catalyzed conjugate addition of aryl iodides (1) onto activated alkenes (2) a.
EntryAryl IodideAlkeneProductYield (%) b
11a Catalysts 10 01320 i0232b Catalysts 10 01320 i0244a82
21b2b Catalysts 10 01320 i0254b81
31c2b Catalysts 10 01320 i0264c43
41d2b Catalysts 10 01320 i0274d84
51e2b Catalysts 10 01320 i0284e74
61f2b Catalysts 10 01320 i0294f77
71g2b Catalysts 10 01320 i0304g73
81h2b Catalysts 10 01320 i0314h77
91i2b Catalysts 10 01320 i0324i80
101a Catalysts 10 01320 i0332c Catalysts 10 01320 i0345a77
111b2c Catalysts 10 01320 i0355b75
121c2c Catalysts 10 01320 i0365c55
131d2c Catalysts 10 01320 i0375d73
141e2c Catalysts 10 01320 i0385e74
151f2c Catalysts 10 01320 i0395f70
161g2c Catalysts 10 01320 i0405g72
171h2c Catalysts 10 01320 i0415h81
181i2c Catalysts 10 01320 i0425i78
191a Catalysts 10 01320 i0432d Catalysts 10 01320 i0446a0
201a Catalysts 10 01320 i0452e Catalysts 10 01320 i0467a0
a Reaction conditions: 1 (1 mmol), 2 (4 mmol), Zn (3 mmol), KOAc (2 mmol), FeCl3·6H2O/L (10 mol%), and H2O (3 mL) at 80 °C for 12 h. b Isolated yields.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Huang, C.-M.; Peng, W.-S.; Liu, L.-J.; Wu, C.-C.; Tsai, F.-Y. Iron-Catalyzed Conjugate Addition of Aryl Iodides onto Activated Alkenes under Air in Water. Catalysts 2020, 10, 1320. https://doi.org/10.3390/catal10111320

AMA Style

Huang C-M, Peng W-S, Liu L-J, Wu C-C, Tsai F-Y. Iron-Catalyzed Conjugate Addition of Aryl Iodides onto Activated Alkenes under Air in Water. Catalysts. 2020; 10(11):1320. https://doi.org/10.3390/catal10111320

Chicago/Turabian Style

Huang, Chung-Min, Wen-Sheng Peng, Ling-Jun Liu, Chien-Chi Wu, and Fu-Yu Tsai. 2020. "Iron-Catalyzed Conjugate Addition of Aryl Iodides onto Activated Alkenes under Air in Water" Catalysts 10, no. 11: 1320. https://doi.org/10.3390/catal10111320

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop