Citation: Zhang Zhen, Gong Li, Zhou Xiao-Yu, Yan Si-Shun, Li Jing, Yu Da-Gang. Radical-Type Difunctionalization of Alkenes with CO₂[J]. Acta Chimica Sinica, ;2019, 77(9): 783-793. doi: 10.6023/A19060208 shu

Radical-Type Difunctionalization of Alkenes with CO₂

Zhang Zhen ^a,b ,
Gong Li ^b ,
Zhou Xiao-Yu ^b ,
Yan Si-Shun ^b ,
Li Jing ^b,, ,
Yu Da-Gang ^b,,

a.
Key Laboratory of Coarse Cereal Processing (Ministry of Agriculture and Rural Affairs), College of Pharmacy and Biological Engineering, Chengdu University, Chengdu 610106
b.
Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064

Corresponding author: Li Jing, jingli@scu.edu.cn Yu Da-Gang, dgyu@scu.edu.cn
Received Date: 12 June 2019
Available Online: 12 September 2019
Fund Project: the National Natural Science Foundation of China 21801025the National Natural Science Foundation of China 21822108the Fok Ying Tung Education Foundation 161013the "973" Project from the Ministry of Science and Technology of China 2015CB856600Project supported by the "973" Project from the Ministry of Science and Technology of China (No. 2015CB856600), the National Natural Science Foundation of China (Nos. 21822108, 21801025), the Fok Ying Tung Education Foundation (No. 161013) and the Fundamental Research Funds for the Central Universities

Figures(15)

CO₂ is an ideal C1 source in chemical transformations. It is of great significance to utilize CO₂ in chemical conversion to synthesize high value-added compounds, including carboxylic acids and carbonyl-containing heterocycles. On the other hand, the difunctionalization of olefins is an important organic reaction, which can efficiently convert easily available olefins into important compounds with structural diversity. However, due to the low reactivity of CO₂ and the difficulty in controlling the selectivity, the difunctionalization of olefins with CO₂ is highly challenging. Recently, the significant progress of radical chemistry has provided new strategies and promoted the development of novel transformations in this field. This Perspective summarizes the recent progress of the radical-type difunctionalization of olefins with CO₂, including the oxy-alkylation, carbocarboxylation, silacarboxylation, thiocarboxylation, and dicarboxylation of alkenes with CO₂. At the same time, we also highlight the mechanism with radicals and four kinds of pathways are proposed:(1) Free radicals attack olefins to form new carbon radical intermediates. The radicals are then oxidized to form carbocations, which are further captured by carbonates or carbamates. It is also possible for direct C-O bonding reaction or sequent C-I and C-O bonds formation. (2) The new carbon radical intermediates, in-situ generated through attack of alkenes with radicals, are reduced via single electron transfer into carbanions, which could attack CO₂to form C-C bonds. (3) CO₂is reduced into CO₂ radical anions in the highly reductive reaction conditions. Once generated, the CO₂ radical anions might attack olefins to form carboxylate bearing more stable carbon radical intermediates (such as benzylic ones) and further form C-C bonds or carbon-heteroatom bonds. (4) Olefins are reduced via single electron transfer into alkenyl free radical anions in the highly reductive reaction conditions. These anions may attack CO₂to form carboxylate bearing carbon radical intermediates and are further reduced to generate carbanions. Finally they may attack another CO₂to form succinic acid derivatives. We point out the challenges and predict the future development in the field, including the more challenging substrates, more reaction types, better selectivities, and deeper mechanistic understanding.
- carbon dioxide,
- olefin,
- difunctionalization,
- radical,
- visible-light photoredox catalysis
1. [1]
2. [2]
3. [3]
  (a) Sasano, K.; Takaya, J.; Iwasawa, N. J. Am. Chem. Soc. 2013, 135, 1251. (b) Sekine, K.; Sadamitsu, Y.; Yamada, T. Org. Lett. 2015, 17, 5706. (c) Moragas, T.; Gaydou, M.; Martin, R. Angew. Chem., Int. Ed. 2016, 55, 5053. (d) Miao, B.; Li, S.; Li, G.; Ma, S. Org. Lett. 2016, 18, 2556. (e) Nogi, K.; Fujihara, T.; Terao, J.; Tsuji, Y. J. Am. Chem. Soc. 2016, 138, 5547. (f) Gholap, S. S.; Takimoto, M.; Hou, Z. Chem. Eur. J. 2016, 22, 8547. (g) Yan, S.-S.; Zhu, L.; Ye, J.-H.; Zhang, Z.; Huang, H.; Zeng, H.; Li, C.-J.; Lan, Y.; Yu, D.-G. Chem. Sci. 2018, 9, 4873. (h) Song, L.; Zhu, L.; Zhang, Z.; Ye, J.-H.; Yan, S.-S.; Han, J.-L.; Yin, Z.-B.; Lan, Y.; Yu, D.-G. Org. Lett. 2018, 20, 3776. (i) Fu, L.; Li, S.; Cai, Z.; Ding, Y.; Guo, X.; Zhou, L.; Yuan, D.; Sun, Q.; Li, G. Nat. Catal. 2018, 1, 469. (j) Xiong, W. F.; Yan, D. H.; Qi, C. R.; Jiang, H. F. Org. Lett. 2018, 20, 672. (k) Wang, S.; Xi, C. J. Org. Lett. 2018, 20, 4131. (l) Song, L.; Cao, G.-M.; Zhou, W.; Ye, J.-H.; Zhang, Z.; Tian, X.-Y.; Li, J.; Yu, D.-G. Org. Chem. Front. 2018, 5, 2086. (m) Cai, Z.; Li, S.; Gao, Y.; Li, G. Adv. Synth. Catal. 2018, 360, 4005. (n) Huang, R.; Li, S.; Fu, L.; Li, G. Asian J. Org. Chem. 2018, 7, 1376. (o) Gao, Y.; Cai, Z.; Li, S.; Li, G. Org. Lett. 2019, 21, 3663. (p) Yan, S.-S.; Wu, D.-S.; Ye, J.-H.; Gong, L.; Zeng, X.; Ran, C.-K.; Gui, Y.-Y.; Li, J.; Yu, D.-G. ACS Catal. 2019, 9, 6987.
4. [4]
  (a) Seo, H; Katcher, M. H.; Jamison, T. F. Nat. Chem. 2017, 9, 453. (b) Meng, Q.; Wang, S.; König, B. Angew. Chem., Int. Ed. 2017, 56, 13426. (c) Shimomaki, K.; Murata, K.; Martin, R.; Iwasawa, N. J. Am. Chem. Soc. 2017, 139, 9467. (d) Liao, L.-L.; Cao, G.-M.; Ye, J.-H.; Sun, G.-Q.; Zhou, W.-J.; Gui, Y.-Y.; Yan, S.-S.; Shen, G.; Yu, D.-G. J. Am. Chem. Soc. 2018, 140, 17338. (e) Ju, T.; Fu, Q.; Ye, J.-H.; Zhang, Z.; Liao, L.-L.; Yan, S.-S.; Tian, X.-Y.; Luo, S.-P.; Li, J.; Yu, D.-G. Angew. Chem. Int. Ed. 2018, 57, 13897. (f) Fan, X.; Gong, X.; Ma, M.; Wang, R.; Walsh, P. J. Nat. Commun. 2018, 9, 4936.
5. [5]
  (a) Wang, H.; Lin, M.-Y.; Fang, H. J.; Chen, T. T.; Lu, J.-X. Chin. J. Chem. 2007, 25, 913. (b) Wang, H.; Du, Y. F.; Lin, M. Y.; Zhang, K.; Lu, J.-X. Chin. J. Chem. 2008, 26, 1745. (c) Jiao, K.; Li, Z.; Xu, X.; Zhang, L.; Li, Y.; Zhang, K.; Mei, T.-S. Org. Chem. Front. 2018, 5, 2244.
6. [6]
  (a) Xin, Z.; Lescot, C.; Friis, S. D.; Daasbjerg, Kim; Skrydstrup, T. Angew. Chem. Int. Ed. 2015, 54, 6862. (b) Zhang, W.; Yang, M. W.; Lv, X. Green Chem. 2016, 18, 4181. (c) Zhang, Z.; Liao, L.-L.; Yan, S.-S.; Wang, L.; He, Y.-Q.; Ye, J.-H.; Li, J.; Zhi, Y.-G.; Yu, D.-G. Angew. Chem., Int. Ed., 2016, 55, 7068. (d) Wang, S.; Shao, P.; Du, G.; Xi, C. J. Org. Chem. 2016, 81, 6672.
7. [7]
  (a) Hu, J.; Ma, J.; Zhu, Q.; Zhang, Z.; Wu, C.; Han, B. Angew. Chem. Int. Ed. 2015, 54, 5399. (b) Gao, X.; Yu, B.; Yang, Z.; Zhao, Y.; Zhang, H.; Hao, L.; Han, B.; Liu, Z. ACS Catal. 2015, 5, 6648. (c) Zhao, Y.; Wu, Y.; Yuan, G.; Hao, L.; Gao, X.; Yang, Z.; Yu, B.; Zhang, H.; Liu, Z. Chem. Asian J. 2016, 11, 2735.
8. [8]
  (a) Li, Y.; Fang, X.; Junge, K.; Beller, M. Angew. Chem. Int. Ed. 2013, 52, 9568. (b) Zhang, Z.; Sun, Q.; Xia, C.; Sun, W. Org. Lett. 2016, 18, 6316. (c) Zhang, Y.; Wang, H.; Yuan, H.; Shi, F. ACS Sustainable Chem. Eng. 2017, 5, 5758. (d) Ren, X.; Zheng, Z.; Zhang, L.; Wang, Z.; Xia, C.; Ding, K. Angew. Chem., Int. Ed. 2017, 56, 310.
9. [9]
  (a) Lehn, J.-M.; Ziessel, R. Proc. Natl. Acad. Sci. USA 1982, 79, 701. (b) Burgess, S. A.; Kendall, A. J.; Tyler, D. R.; Linehan, J. C.; Appel, A. M. ACS Catal. 2017, 7, 3089.
10. [10]
  (a) Pupo, G.; Properzi, R.; List, B. Angew. Chem., Int. Ed. 2016, 55, 6099. (b) Riemer, D.; Mandaviya, B.; Schilling, W.; Götz, A. C.; Kühl, T.; Finger, M.; Das, S. ACS Catal. 2018, 8, 3030. (c) Roy, T.; Kim, M. J.; Yang, Y.; Kim, S.; Kang, G.; Ren, X.; Kadziola, A.; Lee, H.-Y.; Baik, M.-H. Lee, J.-W. ACS Catal. 2019, 9, 6006.
11. [11]
  For selected reviews, see: (a) Cao, M.-Y.; Ren, X.; Lu, Z. Tetrahedron Lett. 2015, 56, 3732. (b) Chen, J.-R.; Yu, X.-Y.; Xiao, W.-J. Synthesis 2015, 47, 604. (c) Koike, T.; Akita, M. Acc. Chem. Res. 2016, 49, 1937. (d) Koike, T.; Akita, M. Chem 2018, 4, 409. (e) Li, W.; Xu, W.; Xie, J.; Yu, S.; Zhu, C. Chem. Soc. Rev. 2018, 47, 654. (f) Wu, X.; Wu, S.; Zhu, C. Tetrahedron Lett. 2018, 59, 1328.
12. [12]
  (a) Yan, M.; Kawamata, Y.; Baran, P. S. Chem. Rev. 2017, 117, 13230. (b) Zhang, Z.; Ye, J.-H.; Wu, D.-S.; Zhou, Y.-Q.; Yu, D.-G. Chem. Asian J. 2018, 13, 2292. (c) Peshkov, V. A.; Pereshivko, O. P.; Nechaev, A. A; Peshkov, A. A.; Vander Eycken, E. V. Chem. Soc. Rev. 2018, 47, 3861. (d) Tortajada, A.; Juliá-Hernández, F.; Börjesson, M.; Moragas, T.; Martin, R. Angew. Chem., Int. Ed. 2018, 57, 15948. (e) Yan, S.-S.; Fu, Q.; Liao, L.-L.; Sun, G.-Q.; Ye, J.-H.; Gong, L.; Bo-Xue, Y.-Z.; Yu, D.-G. Coord. Chem. Rev. 2018, 374, 439. (f) Cao, Y.; He, X.; Wang, N.; Li, H.-R.; He, L.-N. Chin. J. Chem. 2018, 36, 644. (g) Hou, J.; Li, J.-S.; Wu, J. Asian J. Org. Chem. 2018, 7, 1439. (h) Tan, F.; Yin, G. Chin. J. Chem. 2018, 36, 545. (i) Yeung, C. S. Angew. Chem., Int. Ed. 2019, 58, 5492.
13. [13]
  Luan, Y.-X.; Ye, M. Tetrahedron Lett. 2018, 59, 853. doi: 10.1016/j.tetlet.2018.01.035
14. [14]
  (a) Tominaga, K.-I.; Sasaki, Y. Catal. Commun. 2000, 1, 1. (b) Tominaga, K.-i.; Sasaki, Y. J. Mol. Catal. A: Chem. 2004, 220, 159. (c) Liu, Q.; Wu, L.; Fleischer, I.; Selent, D.; Franke, R.; Jackstell, R.; Beller, M. Chem.-Eur. J. 2014, 20, 6888. (d) Tani, Y.; Kuga, K.; Fujihara, T.; Terao, J.; Tsuji, Y. Chem. Commun. 2015, 51, 13020. (e) Gui, Y.-Y.; Hu, N.; Chen, X.-W.; Liao, L.-L.; Ju, T.; Ye, J.-H.; Zhang, Z.; Li, J.; Yu, D.-G. J. Am. Chem. Soc. 2017, 139, 17011.
15. [15]
  Seo, H.; Liu, A.-F.; Jamison, T. F. J. Am. Chem. Soc. 2017, 139, 13969. doi: 10.1021/jacs.7b05942
16. [16]
  (a) Evans, D. A.; Bartroli, J.; Shih, L. T. J. Am. Chem. Soc. 1981, 103, 2127. (b) Pandit, N.; Singla, R. K.; Shrivastava, B. Int. J. Med. Chem. 2012, 2012, 159285. (c) Ed.: Acton, Q. A., Oxazolidinones-Advances in Research and Application, Scholarly Editions, Atlanta, U.S., 2012.
17. [17]
  Ye, J.-H.; Song, L.; Zhou, W.-J.; Ju, T.; Yin, Z.-B.; Yan, S.-S.; Zhang, Z.; Li, J.; Yu, D.-G. Angew. Chem. Int. Ed. 2016, 55, 10022. doi: 10.1002/anie.201603352
18. [18]
  Zhu, L.; Ye, J.-H.; Duan, M.; Qi, X.; Yu, D.-G.; Bai, R.; Lan, Y. Org. Chem. Front. 2018, 5, 633. doi: 10.1039/C7QO00838D
19. [19]
  Ye, J.-H.; Zhu, L.; Yan, S.-S.; Miao, M.; Zhang, X.-C.; Zhou, W.-J.; Li, J.; Lan, Y.; Yu, D.-G. ACS Catal. 2017, 7, 8324. doi: 10.1021/acscatal.7b02533
20. [20]
  Wang, M.-Y.; Cao, Y.; Liu, X.; Wang, N.; He, L.-N.; Li, S.-H. Green Chem. 2017, 19, 1240. doi: 10.1039/C6GC03200A
21. [21]
  Yin, Z.-B.; Ye, J.-H.; Zhou, W.-J.; Zhang, Y.-H.; Ding, L.; Gui, Y.-Y.; Yan, S.-S.; Li, J.; Yu, D.-G. Org. Lett. 2017, 20, 190.
22. [22]
  Zhou, W.-J.; Cao, G.-M.; Sen, G.; Zhu, X.-Y.; Gui, Y.-Y.; Ye, J.-H.; Sun, L.; Liao, L.-L.; Li, J.; Yu, D.-G. Angew. Chem., Int. Ed. 2017, 56, 15683. doi: 10.1002/anie.201704513
23. [23]
  (a) Sun, L.; Ye, J.-H.; Zhou, W.-J.; Zeng, X.; Yu, D.-G. Org. Lett. 2018, 20, 3049. (b) For a very recent work, see: Sun, S.; Zhou, C.; Yu, J.-T.; Cheng, J. Org. Lett. 2019, DOI: 10.1021/acs.org-lett.9b02700.
24. [24]
  Yatham, V. R.; Shen, Y.; Martin, R. Angew. Chem., Int. Ed. 2017, 56, 10915. doi: 10.1002/anie.201706263
25. [25]
  Hou, J.; Ee, A.; Cao, H.; Ong, H.-W.; Xu, J.-H.; Wu J. Angew. Chem., Int. Ed. 2017, 57, 17220.
26. [26]
  Ye, J.-H.; Miao, M.; Huang, H.; Yan, S.-S.; Yin, Z.-B.; Zhou, W.-J.; Yu, D.-G. Angew. Chem., Int. Ed. 2017, 56, 15416. doi: 10.1002/anie.201707862
27. [27]
  Senboku, H.; Komatsu, H.; Fujimura, Y.; Tokuda, M. Synlett 2001, 2001, 418. doi: 10.1055/s-2001-11417
28. [28]
  Yuan, G.-Q.; Jiang, H.-F.; Lin, C.; Liao, S.-J. Electrochim. Acta 2008, 53, 2170. doi: 10.1016/j.electacta.2007.09.023
29. [29]
  Li, C.-H.; Yuan, G.-Q.; Ji, X.-C.; Wang, X.-J.; Ye, J.-S.; Jiang, H.-F. Electrochim. Acta 2011, 56, 1529. doi: 10.1016/j.electacta.2010.06.057
30. [30]
  For a very recent work on phosphonocarboxylation of alkenes with CO₂, see: Fu, Q.; Bo, Z.-Y.; Ye, J.-H.; Ju, T.; Huang, H.; Liao, L.-L.; Yu, D.-G. Nat. Commun. 2019, 10, 3592.
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Radical-Type Difunctionalization of Alkenes with CO2

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Radical-Type Difunctionalization of Alkenes with CO₂