Oxy-Difluoroalkylation of Allylamines with CO2 via Visible-Light

Letter Cite This: Org. Lett. XXXX, XXX, XXX−XXX

pubs.acs.org/OrgLett

Oxy-Difluoroalkylation of Allylamines with CO2 via Visible-Light Photoredox Catalysis Zhu-Bao Yin,†,‡ Jian-Heng Ye,†,‡ Wen-Jun Zhou,†,§ Yi-Han Zhang,† Li Ding,† Yong-Yuan Gui,† Si-Shun Yan,† Jing Li,† and Da-Gang Yu*,† †

Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, P. R. China § College of Chemistry and Chemical Engineering, Neijiang Normal University, Neijiang 641112, P. R. China S Supporting Information *

ABSTRACT: A selective oxy-difluoroalkylation of allylamines with carbon dioxide (CO2) via visible-light photoredox catalysis is reported. These multicomponent reactions are efficient and environmentally friendly to generate a series of important 2-oxazolidinones with functionalized difluoroalkyl groups. The good functional group tolerance, broad substrate scope, easy scalability, mild reaction conditions, and facile functionalization of products provide great potential for application in organic synthesis and pharmaceutical chemistry.

A

pressure (Scheme 1). This method affords important CF2containing 2-oxazolidinones, which are very important motifs in

s is well-known, CO2 is an ideal C1 synthon with characters of nontoxicity, abundance, easy availability, and recyclability.1 Although it is challenging to utilize CO2 due to its thermodynamic stability and kinetic inertness, many methods have been developed to harness CO2 in organic synthesis to construct important carboxylic acids2 and carbonyl-containing heterocycles.3 In spite of this, selective transformations of CO2 for value-added chemicals under mild reaction conditions are still worth exploring. Recently, chemists have developed many methods to generate various kinds of radicals through visible-light photoredox catalysis,4 which features the unique advantages of mild conditions, high efficiency, and facile operation. Although UV light-promoted CO2 utilization in C−C bond formation has been realized by Murakami,5 Jamison,6 and others,7 selective and mild utilization of CO2 in organic synthesis have rarely been reported via visible-light photoredox catalysis.1p For example, Iwasawa8 and König9 independently reported the novel carboxylation with CO2 via photoredox and transition metal (i.e., Rh, Pd, and Ni) dual catalysis. Martin recently also realized an unprecedented carbo-carboxylation of styrenes with radical sources, such as Langlois reagent (CF3SO2Na) and CO2.10 Although Cucatalyzed carboxylative cyclization with CO2 and Togni’s reagent as well as photoinduced radical atom transfer (RAT)/ carboxylative cyclization with CO2 and highly reactive perfluoroalkylation reagents were achieved by our3g and He’s groups,3j the introduction of difluoroalkyl groups, which are usually employed as a bioisostere for an oxygen atom or a carbonyl group and can easily undergo late-stage functionalization,11 along with CO2 to generate important heterocycles via photoredox-catalysis has not been documented. With the continuous interest in CO2 utilization3e,g,i,n,12 and photoredox catalysis,13 we herein report the first photoredox-catalyzed oxydifluoroalkylation of allylamines with CO2 at atmospheric © XXXX American Chemical Society

Scheme 1. Radical Oxy-difluoroalkylation of Allylamines with CO2 via Visible-Light Photoredox Catalysis

drugs, semiconductor devices, and chiral auxiliaries,14 with high efficiency and selectivity using mild reaction conditions. We began our investigation by using N-benzyl-2-phenylprop2-en-1-amine (1a) as the model substrate and bromodifluoroacetate 2a as the difluoroalkylation reagent (Table S1, Supporting Information (SI)). First, we screened various kinds of bases (Table S2, SI) and found that DABCO promoted the reaction to give 3aa in 79% GC-yield with fac-Ir(ppy)3 as the photocatalyst (Table S1, entry 1). Among different solvents (Table S1, entries 1−5), DMF was the best choice. Furthermore, several photocatalysts were investigated. Ru(bpy)3Cl2·6H2O, which is commercially available and much cheaper than iridiumphotocatalysts, was found to be the best choice (Table S1, entries 6−8). Moreover, the catalyst loading can be further reduced to 0.5 mol % (Table S1, entry 9). Importantly, the aminodifluoroalkylation byproduct can hardly be detected (less than 5% yield), indicating the high selectivity. Notably, control experiments showed that both irradiation and photocatalyst were vital to this process (Table S1, entries 10−11). Received: November 16, 2017

A

DOI: 10.1021/acs.orglett.7b03551 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters Scheme 3. Scope of Difluoroalkyl Reagentsa

With the optimized conditions (Table S1, entry 9) in hand, we then explored the substrate scope of the reaction. As shown in Scheme 2, a variety of allylamines were tested to afford the CF2Scheme 2. Scope of Allylaminesa

a

The standard reaction conditions. Yields are those of the isolated products. b36 h. cWith fac-Ir(ppy)3 (2 mol %), 72 h. dWith facIr(ppy)3 (1 mol %). eWith 2h (0.3 mmol), Ru(bpy)3Cl2·6H2O (2 mol %). TIPS = triisopropylsilyl.

this reaction, which has been rarely used as a radical precursor in photoredox catalysis. The mixture of 3ca and 3cb was obtained with the total yield of 54%. Notably, since the phosphonyldifluoromethyl group is a significant moiety in medicinal chemistry,15 the successful production of 3d shows a powerful application of this strategy. Furthermore, CF2H-containing 2oxazolidinones 3h was synthesized efficiently by changing difluoroalkyl bromides to the CF2H radical precursor 2h (Scheme 3B).16 To gain more insight into the reaction mechanism, a series of experiments were conducted (Scheme 4; see the SI for details).

a

The standard reaction conditions. Yields are those of the isolated products. bdr = 1:1. cdr = 10:1. ddr > 19. Piv = pivaloyl.

containing 2-oxazolidinones in moderate to good yields. Besides 1a, the substrate 1b with n-butyl group on the amine nitrogen can also give the product 3ab in a comparably high yield, while those with the phenyl or some common electron-withdrawing groups such as Bz, Boc, Ts, and free amine/alcohol failed, probably due to the weaker nucleophilicity. Both electron-donating and electron-withdrawing groups on the arenes were tolerated. A variety of functional groups, such as fluoro (3ac), chloro (3ad and 3ar), bromo (3ae and 3at), ester (3af, 3ag, and 3an), ether (3ah, 3ak, and 3ap), and amide (3aq), showed good compatibility in this reaction, which provided huge opportunities for downstream transformations. Ortho-, meta-, and parasubstituents of the arenes were amenable to this reaction, providing good to excellent yields of desired products. When the internal alkene 1u with higher steric hindrance was submitted to the standard reaction condition, a mixture of diastereoisomers in a 1:1 ratio was obtained with good yield. Both 1-naphthyl 1v and 2-naphthyl 1w substrates provided the 2-oxazolidones smoothly. Given the great value of spiro-heterocycles, a successful example (3ax) was shown here with good yield and high diastereoselectivity. Notably, we could also get six-membered cyclization product 3ay in moderate yield, demonstrating the superiority of this system. Moreover, it was worth mentioning that the substrate 1z with phenyl group located at the terminal position of the alkene could also undergo this reaction, albeit with a lower yield. However, allylamines without aromatic groups were not suitable substrates in this reaction, which may result from instability of the intermediates. Furthermore, a variety of difluoroalkyl reagents were examined (Scheme 3). Bromodifluoroacetamides (2b, 2e−2g) were examined to give good reactivity. Intriguingly, TIPS protected gem-difluoropropargyl bromide 2c was successfully applied in

Scheme 4. Mechanistic Investigation

Aziridine 3aa′ was obtained in 33% yield without CO2 (Scheme 4, A). However, 3aa′ cannot be converted into 3aa under the standard conditions (Scheme 4B), which indicates that 3aa′ should not be the reactive intermediate. The radical inhibition experiments were conducted by adding 2,2,6,6-tetramethyl-1piperdinyloxy (TEMPO) or 2,6-di-tert-butyl-4-methylphenol (BHT) under the standard reaction conditions, and the reactions were significantly inhibited. The concomitant radical coupling adducts TEMPO−CF2COOEt and BHT−CF2COOEt were B

DOI: 10.1021/acs.orglett.7b03551 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters

reductive products 7 and 8 were obtained with high selectivity and efficiency when using LiAlH4 and NaBH4 as the reductants, respectively. All of these provide great potential for the wide application of this transformation in organic synthesis and pharmaceutical chemistry. Unfortunately, additional deprotection of the Bn group failed so far (see the SI for details). In conclusion, we have successfully developed a visible-light photoredox-catalyzed CO2 utilization to afford various difluoroalkylated 2-oxazolidones under mild conditions. This reaction performs efficiently with broad substrate scope, excellent chemoselectivity, regioselectivity, and good functional-group tolerance. Preliminary mechanistic investigations suggested that difluoroalkyl radical might be involved in this photocatalysis.

also detected (Scheme 4C). Moreover, a radical-clock experiment were performed by using (1-cyclopropylvinyl)benzene 4 as the radical probe. The reaction of a mixture of 1a and 4 gave lower amounts of 3aa and the ring-expanded product 5 (Scheme 4D). These results indicate that this difluoroalkylation/carboxylative cyclization may proceed with a CF2COOEt radical. Moreover, we found that DABCO could quench the photocatalyst prior to substrate 1a, while BrCF2CO2Et could not (see Figure S1−S3 in the SI for details). Thus, we suggest that the single-electron transfer between [Ru(bpy)3Cl2·6H2O]* and DABCO was the key initial step. Based on the above studies, a plausible reaction mechanism is proposed in Scheme 5. The reductive quenching of excited

■

Scheme 5. Proposed Reaction Mechanism

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.7b03551.

■

Experimental procedures and characterization of all products (PDF)

AUTHOR INFORMATION

Corresponding Author

*[email protected] ORCID

Da-Gang Yu: 0000-0001-5888-1494

photocatalyst by DABCO (Epox = +0.69 V vs SCE,17 E[Ru(II)*/ Ru(I)] = +0.77 V) provides Ru(I) (see the SI for more details), which reduces BrCF2COOEt to generate the CF2COOEt radical.18 Then the addition of CF2COOEt radical to carbamate A, which is generated from 1a and CO2 in situ, gives benzylic radical B. Subsequent oxidation of B by excited Ru(II) species and intramolecular cyclization of C afford product 3aa. Other pathways cannot be ruled out at this time. Finally, we carried out the Gram-scale synthesis of 3aa and several important transformations. The Gram-scale synthesis successfully gave a comparable yield of product 3aa (Scheme 6; see the SI for details). The ester group of CF2COOEt efficiently underwent hydrolysis to afford carboxylic acid 6 with 2oxazolidinones scaffold remained unaffected. Moreover, the

Author Contributions ‡

These authors contributed equally.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank Prof. Xingang Zhang (Shanghai Institute of Organic Chemistry) for giving some difluoroalkylation reagents as gifts. We thank the National Natural Science Foundation of China (21502124, 21772129), the “973” Project from the MOST of China (2015CB856600), the “1000-Youth Talents Program”, and the Fundamental Research Funds for the Central Universities for financial support. We also thank the comprehensive training platform of the Specialized Laboratory in the College of Chemistry at Sichuan University for compound testing.

Scheme 6. Gram-Scale Synthesis and Subsequent Functional Group Transformationsa

■

REFERENCES

(1) (a) Sakakura, T.; Choi, J.-C.; Yasuda, H. Chem. Rev. 2007, 107, 2365. (b) Carbon Dioxide as Chemical Feedstock; Aresta, M., Ed.; WileyVCH: Weinheim, 2010. (c) Huang, K.; Sun, C.-L.; Shi, Z.-J. Chem. Soc. Rev. 2011, 40, 2435. (d) Cokoja, M.; Bruckmeier, C.; Rieger, B.; Herrmann, W. A.; Kühn, F. E. Angew. Chem., Int. Ed. 2011, 50, 8510. (e) Tsuji, Y.; Fujihara, T. Chem. Commun. 2012, 48, 9956. (f) Kielland, N.; Whiteoak, C. J.; Kleij, A. W. Adv. Synth. Catal. 2013, 355, 2115. (g) Yeung, C. S.; Dong, V. M. Top. Catal. 2014, 57, 1342. (h) Aresta, M.; Dibenedetto, A.; Angelini, A. Chem. Rev. 2014, 114, 1709. (i) Maeda, C.; Miyazaki, Y.; Ema, T. Catal. Sci. Technol. 2014, 4, 1482. (j) Yu, B.; He, L.N. ChemSusChem 2015, 8, 52. (k) Liu, Q.; Wu, L.; Jackstell, R.; Beller, M. Nat. Commun. 2015, 6, 5933. (l) Liliana, C. T.; Marrucho, I. M. Chem. Soc. Rev. 2016, 45, 2717. (m) Sanz-Pérez, E. S.; Murdock, C. R.; Didas, S. A.; Jones, C. W. Chem. Rev. 2016, 116, 11840. (n) Juliá-Hernández, F.; Gaydou, M.; Serrano, E.; Gemmeren, M.; Martin, R. Top. Curr. Chem. 2016, 374, 45. (o) Zhang, Z.; Ju, T.; Ye, J.-H.; Yu, D.-G. Synlett 2017, 28,

a

See the SI for details. C

DOI: 10.1021/acs.orglett.7b03551 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters 741. (p) Gui, Y.-Y.; Zhou, W.-J.; Yu, D.-G. ChemSusChem 2017, 10, 1337. (2) For selected reviews, see: (a) Correa, A.; Martin, R. Angew. Chem., Int. Ed. 2009, 48, 6201. (b) Yu, D.; Teong, S. P.; Zhang, Y. Coord. Chem. Rev. 2015, 293−294, 279−291. (c) Börjesson, M.; Moragas, T.; Gallego, D.; Martin, R. ACS Catal. 2016, 6, 6739. (d) Wang, S.; Du, G.; Xi, C. Org. Biomol. Chem. 2016, 14, 3666. (e) Zhu, Q.; Wang, L.; Xia, C.; Liu, C. Chin. J. Org. Chem. 2016, 36, 2813. (f) Zhang, S.; Li, X.; He, L.-N. Acta Chim. Sinica 2016, 74, 17. (g) Zhang, W.-Z.; Guo, C.-X.; Lu, X.-B. Chin. J. Catal. 2016, 37, 215. (h) Yuan, G.; Qi, C.; Wu, W.; Jiang, H. Curr. Opin. Green Sust. Chem. 2017, 3, 22. (i) Zhang, L.; Hou, Z. Curr. Opin. Green Sust. Chem. 2017, 3, 17. (j) Wu, X.-F.; Zheng, F. Top Curr. Chem. 2017, 375, 4. (k) Chen, Y.-G.; Xu, X.-T.; Zhang, K.; Li, Y.-Q.; Zhang, L.-P.; Fang, P.; Mei, T.-S. Synthesis 2018, 50, 35. (3) For selected examples, see: (a) Sasano, K.; Takaya, J.; Iwasawa, N. J. Am. Chem. Soc. 2013, 135, 10954. (b) Yoo, W.-J.; Nguyen, T. V. Q.; Kobayashi, S. Angew. Chem., Int. Ed. 2014, 53, 10213. (c) Xin, Z.; Lescot, C.; Friis, S. D.; Daasbjerg, K.; Skrydstrup, T. Angew. Chem., Int. Ed. 2015, 54, 6862. (d) Vara, B. A.; Struble, T. J.; Wang, W.; Dobish, M. C.; Johnston, J. N. J. Am. Chem. Soc. 2015, 137, 7302. (e) 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. (f) Zhang, W.-Z.; Yang, M.-W.; Lu, X.-B. Green Chem. 2016, 18, 4181. (g) 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. (h) Rintjema, J.; Epping, R.; Fiorani, G.; Martin, E.; Escudero-Adan, E. C.; Kleij, A. W. Angew. Chem., Int. Ed. 2016, 55, 3972. (i) Zhang, Z.; Ju, T.; Miao, M.; Han, J.-L.; Zhang, Y.-H.; Zhu, X.-Y.; Ye, J.-H.; Yu, D.-G.; Zhi, Y.-G. Org. Lett. 2017, 19, 396. (j) Wang, M.-Y.; Cao, Y.; Liu, X.; Wang, N.; He, L.-N.; Li, S.-H. Green Chem. 2017, 19, 1240. (k) Liu, X.; He, L.-N. Top. Curr. Chem. 2017, 375, 21. (l) Song, Q.-W.; Zhou, Z.-H.; He, L.-N. Green Chem. 2017, 19, 3707. (m) Zhang, W.-Z.; Zhang, N.; Guo, C.-X.; Lu, X.-B. Chin. J. Org. Chem. 2017, 37, 1309. (n) 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. (4) For recent reviews, see: (a) Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C. Chem. Rev. 2013, 113, 5322. (b) Xi, Y.; Yi, H.; Lei, A. Org. Biomol. Chem. 2013, 11, 2387. (c) Hari, D. P.; König, B. Angew. Chem., Int. Ed. 2013, 52, 4734. (d) Dai, X.-J.; Xu, X.-L.; Li, X.-N. Chin. J. Org. Chem. 2013, 33, 2046. (e) Schultz, D. M.; Yoon, T. P. Science 2014, 343, 1239176. (f) Xie, J.; Jin, H.; Xu, P.; Zhu, C. Tetrahedron Lett. 2014, 55, 36. (g) Beatty, J. W.; Stephenson, C. R. J. Acc. Chem. Res. 2015, 48, 1474. (h) Meggers, E. Chem. Commun. 2015, 51, 3290. (i) Wang, C.; Lu, Z. Org. Chem. Front. 2015, 2, 179. (j) Chen, J.-R.; Hu, X.-Q.; Lu, L.-Q.; Xiao, W.-J. Chem. Soc. Rev. 2016, 45, 2044. (k) Pan, X.; Xia, H.; Wu, J. Org. Chem. Front. 2016, 3, 1163. (l) Sun, X.; Yu, S. Chin. J. Org. Chem. 2016, 36, 239. (m) Goddard, J.-P.; Ollivier, C.; Fensterbank, L. Acc. Chem. Res. 2016, 49, 1924. (n) Romero, N. A.; Nicewicz, D. A. Chem. Rev. 2016, 116, 10075. (o) Tellis, J. C.; Kelly, C. B.; Primer, D. N.; Jouffroy, M.; Patel, N. R.; Molander, G. A. Acc. Chem. Res. 2016, 49, 1429. (p) Hopkinson, M. N.; Tlahuext-Aca, A.; Glorius, F. Acc. Chem. Res. 2016, 49, 2261. (q) Fabry, D. C.; Rueping, M. Acc. Chem. Res. 2016, 49, 1969. (r) Zhang, J.; Chen, Y. Acta Chim. Sinica 2017, 75, 41. (s) Zhong, J.-J.; Meng, Q.-Y.; Chen, B.; Tung, C.-H.; Wu, L.-Z. Acta Chim. Sinica 2017, 75, 34. (t) Chen, J.-R.; Yan, D.-M.; Wei, Q.; Xiao, W.J. ChemPhotoChem. 2017, 1, 148. (5) (a) Masuda, Y.; Ishida, N.; Murakami, M. J. Am. Chem. Soc. 2015, 137, 14063. (b) Ishida, N.; Masuda, Y.; Uemoto, S.; Murakami, M. Chem. - Eur. J. 2016, 22, 6524. (6) (a) Seo, H.; Katcher, M. H.; Jamison, T. F. Nat. Chem. 2017, 9, 453. (b) Seo, H.; Liu, A.; Jamison, T. F. J. Am. Chem. Soc. 2017, 139, 13969. (7) (a) Tazuke, S.; Kazama, S.; Kitamura, N. J. Org. Chem. 1986, 51, 4548. (b) Ito, Y.; Uozu, Y.; Matsuura, T. J. Chem. Soc., Chem. Commun. 1988, 562. (c) Tagaya, H.; Onuki, M.; Tomioka, Y.; Wada, Y.; Karasu, M.; Chiba, K. Bull. Chem. Soc. Jpn. 1990, 63, 3233. (d) Aresta, M.; Dibenedetto, A.; Baran, T.; Wojtyła, S.; Macyk, W. Faraday Discuss. 2015, 183, 413. For other examples of light-driven CO2 transformations, see: (e) Padwa, A.; Wetmore, S. I. J. Am. Chem. Soc. 1974, 96, 2414. (f) Komatsu, M.; Aida, T.; Inoue, S. J. Am. Chem. Soc. 1991, 113, 8492. (g) Morgenstern, D. A.; Wittrig, R. E.; Fanwick, P. E.; Kubiak, C. P.

J. Am. Chem. Soc. 1993, 115, 6470. (h) Fujiwara, H.; Kanemoto, M.; Ankyu, H.; Murakoshi, K.; Wada, Y.; Yanagida, S. J. Chem. Soc., Perkin Trans. 2 1997, 2, 317. (i) Baran, T.; Dibenedetto, A.; Aresta, M.; Kruczała, K.; Macyk, W. ChemPlusChem 2014, 79, 708. (j) Dibenedetto, A.; Zhang, J.; Trochowski, M.; Angelini, A.; Macyk, W.; Aresta, M. J. CO2 Util. 2017, 20, 97. (8) (a) Shimomaki, K.; Murata, K.; Martin, R.; Iwasawa, N. J. Am. Chem. Soc. 2017, 139, 9467. (b) Murata, K.; Numasawa, N.; Shimomaki, K.; Takaya, J.; Iwasawa, N. Chem. Commun. 2017, 53, 3098. (9) Meng, Q.-Y.; Wang, S.; König, B. Angew. Chem., Int. Ed. 2017, 56, 13426. (10) Yatham, V. R.; Shen, Y.; Martin, R. Angew. Chem., Int. Ed. 2017, 56, 10915. (11) (a) Gu, J.-W.; Min, Q.-Q.; Yu, L.-C.; Zhang, X. Angew. Chem., Int. Ed. 2016, 55, 12270. (b) Zhao, H.-Y.; Feng, Z.; Luo, Z.; Zhang, X. Angew. Chem., Int. Ed. 2016, 55, 10401. (c) Xu, P.; Wang, G.; Zhu, Y.; Li, W.; Cheng, Y.; Li, S.; Zhu, C. Angew. Chem., Int. Ed. 2016, 55, 2939. (d) Yerien, D. E.; Barata-Vallejo, S.; Postigo, A. Chem. - Eur. J. 2017, 23, 14676. (12) (a) 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. (b) 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. (13) (a) Gui, Y.-Y.; Sun, L.; Lu, Z.-P.; Yu, D.-G. Org. Chem. Front. 2016, 3, 522. (b) Gui, Y.-Y.; Liao, L.-L.; Sun, L.; Zhang, Z.; Ye, J.-H.; Shen, G.; Lu, Z.-P.; Zhou, W.-J.; Yu, D.-G. Chem. Commun. 2017, 53, 1192. (c) Liao, L.-L.; Gui, Y.-Y.; Zhang, X.-B.; Shen, G.; Liu, H.-D.; Zhou, W.J.; Li, J.; Yu, D.-G. Org. Lett. 2017, 19, 3735. (d) Zhou, W.-J.; Cao, G.-M.; Shen, 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. (e) Gui, Y.-Y.; Chen, X.W.; Zhou, W.-J.; Yu, D.-G. Synlett 2017, 28, 2581. (f) Gui, Y.-Y.; Wang, Z.-X.; Zhou, W.-J.; Liao, L.-L.; Song, L.; Yin, Z.-B.; Li, J.; Yu, D.-G. Asian J. Org. Chem. 2018, DOI: 10.1002/ajoc.201700450. (14) Oxazolidinones: Advances in Research and Application; Acton, Q. A., Ed.; Scholarly eds: Atlanta, GA, 2012. (15) (a) Benayoud, F.; Hammond, G. B. Chem. Commun. 1996, 12, 1447. (b) Burke, T. R.; Lee, K. Acc. Chem. Res. 2003, 36, 426. (c) Romanenko, V. D.; Kukhar, V. P. Chem. Rev. 2006, 106, 3868. (16) Rong, J.; Deng, L.; Tan, P.; Ni, C.; Gu, Y.; Hu, J. Angew. Chem., Int. Ed. 2016, 55, 2743. (17) Barham, J. P.; John, M. P.; Murphy, J. A. J. Am. Chem. Soc. 2016, 138, 15482. (18) Sumino, S.; Uno, M.; Fukuyama, T.; Ryu, I.; Matsuura, M.; Yamamoto, A.; Kishikawa, Y. J. Org. Chem. 2017, 82, 5469.

D

DOI: 10.1021/acs.orglett.7b03551 Org. Lett. XXXX, XXX, XXX−XXX