Chemodivergent Couplings of N-Arylureas and Methyleneoxetanones

8 hours ago - Despite these impressive progresses, there is still room for further devising innovative reaction modes involving selective C–H functi...
0 downloads 0 Views 1MB Size
Download PDF
Letter Cite This: Org. Lett. XXXX, XXX, XXX−XXX

pubs.acs.org/OrgLett

Chemodivergent Couplings of N‑Arylureas and Methyleneoxetanones via Rh(III)-Catalyzed and Solvent-Controlled C−H Activation Guoxun Zhu,†,§ Wendi Shi,†,‡,§ Hui Gao,‡ Zhi Zhou,*,‡ Huacan Song,† and Wei Yi*,‡ †

School of Chemical Engineering and Technology, Sun Yat-sen University, Guangzhou, Guangdong 510275, China Key Laboratory of Molecular Target & Clinical Pharmacology and State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong 511436, China

‡

Downloaded by UNIV AUTONOMA DE COAHUILA at 11:32:11:290 on May 24, 2019 from https://pubs.acs.org/doi/10.1021/acs.orglett.9b01333.

S Supporting Information *

ABSTRACT: The efficient couplings of diverse N-arylureas and methyleneoxetanones have been realized via Rh(III)catalyzed and solvent-controlled chemoselective C−H functionalization, which involved the tunable β-H elimination and β-O elimination processes, thereby giving divergent access to quinolin-2(1H)-ones and ortho-allylated N-arylureas with broad substrate compatibility and good functional group tolerance. the divergent synthetic utilities of the transformations have also been exemplified by subsequently tandem C−H allylation, unsymmetrical C−H functionalization, alternative reaction mode, as well as removal of the carbamoyl group.

O

Scheme 1. TM-Catalyzed Chemoselective Ring-Opening Transformations of Methyleneoxetanones

ver the past decades, transition metal (TM)-catalyzed C−H functionalization has emerged as a powerful and promising approach for the construction of diverse scaffolds from simple and readily available raw materials.1 Among the notable advances in this field, the development of novel and efficient strategies including catalyst-mediated,2 directing group (DG)-enabled,3 or reaction conditions-controlled4 methodology in modifying either chemo-, regio-, or stereoselectivity has proven to be versatile for the divergent access to a variety of frameworks. Despite these impressive progresses, there is still room for further devising innovative reaction modes involving selective C−H functionalization for the direct synthesis of privileged structural motifs. Methyleneoxetanones, bearing the four-membered lactone ring, are easily accessible and valuable synthetic building blocks in organic synthesis.5 The presence of the alkene moiety and the lactone unit in methyleneoxetanones endows diversified reactivity for this skeleton, among which the selective acyl or alkyl C−O bond cleavage was respectively realized to reveal different ring-opening transformations (Scheme 1, top). In 2017, Howell and co-workers disclosed a Pd(II)-catalyzed acyl C−O bond activation/amidation reaction to furnish β-hydroxy amides with complete chemo- and regioselectivity.5a Almost simultaneously, an alternative alkyl C−O bond cleavage ringopening reaction of methyleneoxetanones was achieved by Li’s group under the Rh(III)-catalyzed conditions, delivering the substituted propenoic acids via anti β-O elimination process.5b Whereafter, we also developed a Rh(III)-catalyzed tandem C− H activation/alkyl C−O bond cleavage/[3 + 3] annulation of N-phenoxyacetamides with methyleneoxetanones for the efficient synthesis of 2H-chromene-3-carboxylic acids.5d Inspired by these developments and in combination with our continuing efforts to search and develop the novel and feasible © XXXX American Chemical Society

C−H functionalization modes for the rapid construction of prevalent heterocycles,6 we are committed to further exploring the reaction diversity of methyleneoxetanone unit. In a search for versatile and synthetically useful DGs that enable attractive transformations with methyleneoxetanones, we turned our attention to N-arylureas. Urea moiety represents a prevalent pharmacophore and widely existed in natural products and biological active molecules.7 Consequently, the urea group has recently been widely explored as a transformable DG in the field of TM-catalyzed C−H functionalization with alkynes,8 alkenes9 and other coupling partners.10 Received: April 16, 2019

A

DOI: 10.1021/acs.orglett.9b01333 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters

methyleneoxetanones were meticulously assessed to demonstrate the versatility of these protocols. As shown in Scheme 2,

Taking advantages of diversified reactivity with methyleneoxetanones and N-arylureas, we would like to present herein the Rh(III)-catalyzed and solvent-controlled chemoselective C−H activation/[3 + 3] annulation or allylation for the divergent access to quinolin-2(1H)-ones and ortho-allylated N-arylurea derivatives, in which the selective acyl and alkyl C−O bond cleavage were respectively realized by the rational choice of the solvent (Scheme 1, bottom). In preliminary experiments, 1,1-dimethyl-3-phenylurea 1a was treated with methyleneoxetanone 2a under Rh(III)catalyzed conditions in methanol, and the [3 + 3] annulation product quinolin-2(1H)-one 3a was obtained in a catalytic yield (Table 1, entry 1). The addition of Cu(OAc)2 as the

Scheme 2. Reaction Scope for the Synthesis of Quinolin2(1H)-onesa

Table 1. Optimization of Reaction Conditionsa

yield (%)b entry 1 2 3 4 5 6 7 8c 9c 10 11 12 13d

additive

solvent

3a

Cu(OAc)2 Cu(OAc)2 Cu(OAc)2 Cu(OAc)2 AgOAc K2S2O8 Cu(OAc)2 Cu(OAc)2 HOAc AgOAc Zn(OAc)2 Zn(OAc)2

MeOH MeOH DCE toluene THF THF THF THF TFE TFE TFE TFE TFE

trace 24 28 25 57 34

4a

trace

a

Reaction conditions A: 1 (0.2 mmol), 2 (0.3 mmol), [Cp*RhCl2]2 (2.5 mol %), AgSbF6 (20 mol %), and Cu(OAc)2 (1 equiv) in THF (0.1 M) at 60 °C for 24 h under air; isolated yields were reported. b Performed on a 2.0 mmol scale.

76 34 36 24 42 70

a variety of 1,1-dimethyl-3-phenylureas bearing different substituents at either para-, ortho-, or meta-position were well tolerated under conditions A, leading to the smooth construction of various quinolin-2(1H)-one derivatives (3a− p) in moderate to good yields. Of note, the C−H bond cleavage occurred at the less-hindered site exclusively (3n−p) when meta-substituted phenylureas were employed, showing the good regioselectivity of the Rh(III) catalysis. Moreover, naphthalene substrate was also good reactant for this transformation, furnishing the desired product 3q in 51% yield. Interestingly, several methyleneoxetanones bearing various substituents including benzyl (3r), cycloalkyl (3s), and alkyl (3t and 3u) were tested under the standard conditions to result in good compatibility, revealing that the developed Rh(III)-catalyzed [3 + 3] annulation was broadly applicable for the synthesis of quinolin-2(1H)-one skeleton. To better probe the potential of these protocols for the divergent synthesis of diverse frameworks, we then turned our attention to examining the reaction scope of ortho-allylated phenylureas under conditions B (Scheme 3). As expected, various commonly encountered functional groups including methoxyl (4b and 4o), alkyl (4c−e, 4l, and 4m), halogens (4f−h), phenyl (4i), acetyl (4j), and ester group (4k) were well tolerated to deliver the corresponding products smoothly. It should be emphasized that, the position of the substituent played a crucial role in the reaction efficiency since the orthosubstituted phenylureas were less reactive than those para- or meta-substituted substrates, thereby leading to the low yields of the desired C−H allylation products (e.g., 37% for 4l) together with the recovery of 1,1-dimethyl-3-phenylureas. A diverse array of methyleneoxetanones was next examined to further explore the reaction scope. As a result, several derivatives of 3-

a

Reaction conditions: 1a (0.2 mmol), 2a (0.2 mmol), [Cp*RhCl2]2 (2.5 mol %), and additive (1 equiv) in solvent (0.1 M) at 60 °C for 24 h without exclusion of air or moisture. bIsolated yields. c2a (1.5 equiv). d2a (1.3 equiv).

external oxidant increased the yield of the desired product (entry 2). The switching of the solvent from MeOH to other reaction media revealed that THF was the ideal solvent for this [3 + 3] annulation (entries 2−5). Further screening of the additive showed that Cu(OAc)2 was optimal (entries 5−7). Excitingly, an alternative C−H allylation proceeded smoothly by simply switching the reaction solvent to TFE (entry 9), leading to the generation of ortho-allylated phenylurea product 4a. Enlightened by the tunable chemoselectivity and the intriguing structures of the two products, we next screened several experimental parameters (entries 8−13), including additives, reaction temperature and the proportion of substrates, to define the optimal reaction conditions (see Table S1 in the Supporting Information for detailed optimization studies). After a number of trials, we were pleased to identify the optimized conditions for both transformations, giving the desired 3a and 4a in 76% and 70% yields, respectively. With the optimal conditions in hand, we next investigated the scope and generality of this methodology for the efficient synthesis of both quinolin-2(1H)-ones and ortho-allylated phenylureas. A series of 1,1-dimethyl-3-phenylureas as well as B

DOI: 10.1021/acs.orglett.9b01333 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters Scheme 3. Substrate Scope for C−H Allylationa

Scheme 4. Divergent Synthetic Utility

a

Reaction conditions B: 1 (0.2 mmol), 2 (0.26 mmol), [Cp*RhCl2]2 (2.5 mol %), AgSbF6 (20 mol %), and Zn(OAc)2 (1 equiv) in TFE (0.1 M) at 60 °C for 24 h under air; isolated yields were reported. b Performed on a 2.0 mmol scale.

block the subsequent cyclization, we rationally devised −OCONMe2 as the urea analogue. The reaction proceeded smoothly for 5 h to furnish the product 11 in 21% isolated yield under the THF-controlled conditions (eq 1), suggesting that the initial C−H alkenylation product bearing a methyleneoxetanone moiety might be used as the precursor of the [3 + 3] annulation.

methylene-4-oxetan-2-one bearing different substituents at the 4-position were all compatible with this transformation, thus giving direct access to the corresponding carboxylic acid products (4q−t) in moderate to good yields (52−95%). Having established the practical approaches for the divergent synthesis of both quinolin-2(1H)-one and ortho-allylated phenylurea skeletons, we were next intrigued to further investigate the synthetic potentials of such transformations. Considering that urea moiety has been demonstrated as the effective DG for diverse C−H functionalization, we rationally proposed the cascade processes involving tandem C−H bond cleavage/functionalization. Gratifyingly, when 3.0 equiv of 2a was subjected to the TFE-controlled C−H allylation conditions B, the diallylated phenylurea derivative 5 was obtained as the major product (Scheme 4a). In addition, by sequentially adding different methyleneoxetanones, the desired unsymmetrical diallylation proceeded smoothly to generate the product 6 in a 45% isolated yield.11 Other transformations involving the secondary C−H bond cleavage via one-pot cascade unsymmetrical C−H functionalization were next examined under conditions B according to precedent literatures.9f The results revealed that the commonly encountered coupling partner such as alkene was compatible to this strategy, furnishing the corresponding product 7 in a moderate yield (Scheme 4b). It was worth noting that an alternative [3 + 3] annulation was facilely realized to yield the 3,4-dihydroquinolin-2(1H)-one derivative 8 under TFEcontrolled conditions by simply increasing the temperature up to 100 °C (Scheme 4c), demonstrating the divergent synthetic utility of this protocol. Moreover, the deprotection of 4a was achieved by the treatment with NaOH (50%, aq.) in ethanol at 80 °C, affording the free NH-quinolin-2(1H)-one derivative 9 in 98% yield (Scheme 4d). To gain more insights into the reaction mechanism, we next conducted the control experiment to capture the potent reaction intermediate. Considering the possibility that the inhibition of the nucleophilic −NHCONMe2 moiety might

On the basis of the above experimental results and literature precedents,5b,d,8−10 a plausible mechanism involving solventcontrolled chemoselective C−H activation process is proposed (Scheme 5). Initially, the active cationic Cp*Rh(III) species is generated through anion exchange, followed by the coordination with 1a and ortho C−H bond cleavage to yield the sixScheme 5. Proposed Catalytic Cycle

C

DOI: 10.1021/acs.orglett.9b01333 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters membered rhodacycle intermediate A.12 Subsequent regioselective migratory insertion of the alkene moiety of 2a into the C−Rh bond forms the intermediate B, from which two distinguished pathways are involved to give different products in a solvent-controlled chemoselective manner. In path a, the tandem β-H elimination/intramolecular cyclization13 proceeds facilely by employing the species C as the active intermediate, delivering the [3 + 3] annulated quinolin-2(1H)-one 3a along with Cp*Rh(I) species. Alternatively, in path b, the ringopening process of cyclic ester is involved via Lewis acidassisted β-O elimination5b,14 under TFE-mediated conditions to give the intermediate D, which undergoes protonolysis to release the final carboxylic acid 4a. In summary, by selectively tuning the acyl or alkyl C−O bond cleavage of the four-membered lactone unit in methyleneoxetanones, the mild Rh(III)-catalyzed and solvent-controlled chemoselective C−H functionalization of Narylureas has been developed for the divergent synthesis of both quinolin-2(1H)-ones and ortho-allylated arylurea derivatives. These transformations were demonstrated to be practical with good functional group tolerance, exclusive and tunable chemoselectivity, as well as profound potential of the synthetic utility. Further investigations on the detailed mechanism and the synthetic application of such protocols are in progress.

■

7179. (g) Yang, S.; Shi, M. Acc. Chem. Res. 2018, 51, 1667. (h) Tang, X.; Wu, W.; Zeng, W.; Jiang, H. Acc. Chem. Res. 2018, 51, 1092. (i) Karimov, R. R.; Hartwig, J. F. Angew. Chem., Int. Ed. 2018, 57, 4234. (j) Saint-Denis, T. G.; Zhu, R.-Y.; Chen, G.; Wu, Q.-F.; Yu, J.Q. Science 2018, 359, eaao4798. (k) Gandeepan, P.; Ackermann, L. Chem. 2018, 4, 199. (l) Mihai, M. T.; Genov, G. R.; Phipps, R. J. Chem. Soc. Rev. 2018, 47, 149. (m) Chu, J. C. K.; Rovis, T. Angew. Chem., Int. Ed. 2018, 57, 62. (2) For selected reviews, see: (a) Tiwari, V. K.; Kapur, M. Org. Biomol. Chem. 2019, 17, 1007. (b) Park, J.; Chang, S. Chem. - Asian J. 2018, 13, 1089. (c) Lied, F.; Patra, T.; Glorius, F. Isr. J. Chem. 2017, 57, 945. (d) Alderson, J. M.; Corbin, J. R.; Schomaker, J. M. Acc. Chem. Res. 2017, 50, 2147. (e) Ping, L.; Chung, D. S.; Bouffard, J.; Lee, S. Chem. Soc. Rev. 2017, 46, 4299. (3) For selected examples, see: (a) Guimond, N.; Gorelsky, S. I.; Fagnou, K. J. Am. Chem. Soc. 2011, 133, 6449. (b) Ji, C.; Xu, Q.; Shi, M. Adv. Synth. Catal. 2017, 359, 974. (c) Wu, J.-Q.; Zhang, S.-S.; Gao, H.; Qi, Z.; Zhou, C.-J.; Ji, W.-W.; Liu, Y.; Chen, Y.; Li, Q.; Li, X.; Wang, H. J. Am. Chem. Soc. 2017, 139, 3537. (d) Fukui, Y.; Liu, P.; Liu, Q.; He, Z.-T.; Wu, N.-Y.; Tian, P.; Lin, G.-Q. J. Am. Chem. Soc. 2014, 136, 15607. (e) Huang, X.-C.; Yang, X.-H.; Song, R.-J.; Li, J.-H. J. Org. Chem. 2014, 79, 1025. (f) Davis, T. A.; Hyster, T. K.; Rovis, T. Angew. Chem., Int. Ed. 2013, 52, 14181. (4) For selected examples, see: (a) Chung, D. S.; Lee, J. S.; Ryu, H.; Park, J.; Kim, H.; Lee, J. H.; Kim, U. B.; Lee, W. K.; Baik, M.-H.; Lee, S. Angew. Chem., Int. Ed. 2018, 57, 15460. (b) Wang, Y.; Du, C.; Wang, Y.; Guo, X.; Fang, L.; Song, M.-P.; Niu, J.-L.; Wei, D. Adv. Synth. Catal. 2018, 360, 2668. (c) Xu, Y.; Zheng, G.; Yang, X.; Li, X. Chem. Commun. 2018, 54, 670. (d) Feng, R.; Ning, H.; Su, H.; Gao, Y.; Yin, H.; Wang, Y.; Yang, Z.; Qi, C. J. Org. Chem. 2017, 82, 10408. (e) Su, B.; Wei, J.-B.; Wu, W.-L.; Shi, Z.-J. ChemCatChem 2015, 7, 2986. (f) Zheng, J.; Zhang, Y.; Cui, S. Org. Lett. 2014, 16, 3560. (g) Liu, G.; Shen, Y.; Zhou, Z.; Lu, X. Angew. Chem., Int. Ed. 2013, 52, 6033. (5) (a) Malapit, C. A.; Luvaga, I. K.; Caldwell, D. R.; Schipper, N. K.; Howell, A. R. Org. Lett. 2017, 19, 4460. (b) Xia, J.; Kong, L.; Zhou, X.; Zheng, G.; Li, X. Org. Lett. 2017, 19, 5972. (c) Malapit, C. A.; Caldwell, D. R.; Sassu, N.; Milbin, S.; Howell, A. R. Org. Lett. 2017, 19, 1966. (d) Zhou, Z.; Bian, M.; Zhao, L.; Gao, H.; Huang, J.; Liu, X.; Yu, X.; Li, X.; Yi, W. Org. Lett. 2018, 20, 3892. (e) Li, P.; Lu, B.; Fu, C.; Ma, S. Org. Biomol. Chem. 2013, 11, 98. (f) Raju, R.; Howell, A. R. Org. Lett. 2006, 8, 2139. (6) For recently selected examples, see: (a) Yi, W.; Li, L.; Chen, H.; Ma, K.; Zhong, Y.; Chen, W.; Gao, H.; Zhou, Z. Org. Lett. 2018, 20, 6812. (b) Yi, W.; Chen, W.; Liu, F.-X.; Zhong, Y.; Wu, D.; Zhou, Z.; Gao, H. ACS Catal. 2018, 8, 9508. (c) Chen, W.; Liu, F.-X.; Gong, W.; Zhou, Z.; Gao, H.; Shi, J.; Wu, B.; Yi, W. Adv. Synth. Catal. 2018, 360, 2470. (d) Gong, W.; Zhou, Z.; Shi, J.; Wu, B.; Huang, B.; Yi, W. Org. Lett. 2018, 20, 182. (e) Wu, W.; Guo, Y.; Xu, X.; Zhou, Z.; Zhang, X.; Wu, B.; Yi, W. Org. Chem. Front. 2018, 5, 1713. (f) Xu, X.; Yang, Y.; Zhang, X.; Yi, W. Org. Lett. 2018, 20, 566. (7) (a) Chen, J.-N.; Wu, D.-W.; Li, T.; Yang, K.-J.; Cheng, L.; Zhou, Z.-P.; Pu, S.-M.; Lin, W.-H. Curr. Top. Med. Chem. 2017, 17, 3099. (b) Ghosh, A. K.; Brindisi, M.; Sarkar, A. ChemMedChem 2018, 13, 2351. (c) Jagtap, A. D.; Kondekar, N. B.; Sadani, A. A.; Chern, J.-W. Curr. Med. Chem. 2017, 24, 622. (8) (a) Zhang, Z.-Z.; Liu, B.; Xu, J.-W.; Yan, S.-Y.; Shi, B.-F. Org. Lett. 2016, 18, 1776. (b) Hou, Z.-W.; Mao, Z.-Y.; Zhao, H.-B.; Melcamu, Y. Y.; Lu, X.; Song, J.; Xu, H.-C. Angew. Chem., Int. Ed. 2016, 55, 9168. (c) Jiang, P.; Xu, Y.; Sun, F.; Liu, X.; Li, F.; Yu, R.; Li, Y.; Wang, Q. Org. Lett. 2016, 18, 1426. (d) Kathiravan, S.; Nicholls, I. A. Chem. Commun. 2014, 50, 14964. (9) (a) Chen, S.-S.; Wu, M.-S.; Han, Z.-Y. Angew. Chem., Int. Ed. 2017, 56, 6641. (b) Zhang, G.; Luo, Y.; Wang, Y.; Zhang, L. Angew. Chem., Int. Ed. 2011, 50, 4450. (c) Houlden, C. E.; Bailey, C. D.; Ford, J. G.; Gagné, M. R.; Lloyd-Jones, G. C.; Booker-Milburn, K. I. J. Am. Chem. Soc. 2008, 130, 10066. (d) Manna, M. K.; Hossian, A.; Jana, R. Org. Lett. 2015, 17, 672. (e) Wang, L.; Liu, S.; Li, Z.; Yu, Y.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.9b01333. Experimental procedures, characterization of products, and copies of 1H and 13C NMR spectra (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Hui Gao: 0000-0002-8736-4485 Zhi Zhou: 0000-0002-6521-8946 Wei Yi: 0000-0001-7936-9326 Author Contributions §

G.Z. and W.S. contributed equally.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank the NSFC (21877020), Guangdong Natural Science Funds for Distinguished Young Scholar (2017A030306031), and Natural Science Foundation of Guangdong Province (2018A030313274) for financial support of this study.

■

REFERENCES

(1) For recently selected reviews since 2018, see: (a) Gandeepan, P.; Müller, T.; Zell, D.; Cera, G.; Warratz, S.; Ackermann, L. Chem. Rev. 2019, 119, 2192. (b) Maraswami, M.; Loh, T.-P. Synthesis 2019, 51, 1049. (c) Huang, Z.; Lumb, J.-P. ACS Catal. 2019, 9, 521. (d) Wang, C.-S.; Dixneuf, P. H.; Soulé, J.-F. Chem. Rev. 2018, 118, 7532. (e) Sauermann, N.; Meyer, T. H.; Qiu, Y.; Ackermann, L. ACS Catal. 2018, 8, 7086. (f) Ma, C.; Fang, P.; Mei, T.-S. ACS Catal. 2018, 8, D

DOI: 10.1021/acs.orglett.9b01333 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters Org. Lett. 2011, 13, 6137. (f) Lv, H.; Shi, J.; Huang, J.; Zhang, C.; Yi, W. Org. Biomol. Chem. 2017, 15, 7088. (10) For representative examples, see: (a) Wang, C.-M.; Tang, K.-X.; Gao, T.-H.; Chen, L.; Sun, L.-P. J. Org. Chem. 2018, 83, 8315. (b) Jiang, P.; Li, F.; Xu, Y.; Liu, Q.; Wang, J.; Ding, H.; Yu, R.; Wang, Q. Org. Lett. 2015, 17, 5918. (c) Patel, P.; Borah, G. Eur. J. Org. Chem. 2017, 2017, 2272. (d) Lv, H.; Shi, J.; Wu, B.; Guo, Y.; Huang, J.; Yi, W. Org. Biomol. Chem. 2017, 15, 8054. (11) For selected examples on unsymmetrical difunctionalization of two ortho C−H bonds, see: (a) Ghosh, K.; Shankar, M.; Rit, R. K.; Dubey, G.; Bharatam, P. V.; Sahoo, A. K. J. Org. Chem. 2018, 83, 9667. (b) Li, W.; Zhao, Y.; Mai, S.; Song, Q. Org. Lett. 2018, 20, 1162. (c) Wu, Y.; Chen, Z.; Yang, Y.; Zhu, W.; Zhou, B. J. Am. Chem. Soc. 2018, 140, 42. (d) Ghosh, K.; Rit, R. K.; Ramesh, E.; Sahoo, A. K. Angew. Chem., Int. Ed. 2016, 55, 7821. (e) Kim, H. J.; Ajitha, M. J.; Lee, Y.; Ryu, J.; Kim, J.; Lee, Y.; Jung, Y.; Chang, S. J. Am. Chem. Soc. 2014, 136, 1132. (f) Sarkar, D.; Melkonyan, F. S.; Gulevich, A. V.; Gevorgyan, V. Angew. Chem., Int. Ed. 2013, 52, 10800. (12) (a) Nishikata, T.; Abela, A. R.; Huang, S.; Lipshutz, B. H. Beilstein J. Org. Chem. 2016, 12, 1040. (b) Cheng, G.; Lim, R. K. V.; Ramil, C. P.; Lin, Q. Chem. Commun. 2014, 50, 11679. (c) Nickerson, D. M.; Mattson, A. E. Chem. - Eur. J. 2012, 18, 8310. (d) Houlden, C. E.; Hutchby, M.; Bailey, C. D.; Ford, J. G.; Tyler, S. N. G.; Gagne, M. R.; Lloyd-Jones, G. C.; Booker-Milburn, K. I. Angew. Chem., Int. Ed. 2009, 48, 1830. (13) For selected examples involving intramolecular cyclization, see: (a) Ikemoto, H.; Tanaka, R.; Sakata, K.; Kanai, M.; Yoshino, T.; Matsunaga, S. Angew. Chem., Int. Ed. 2017, 56, 7156. (b) Patel, P.; Borah, G. Chem. Commun. 2017, 53, 443. (c) Wu, Z.-J.; Li, Y.-Q.; Huang, Z.-Z. Eur. J. Org. Chem. 2016, 2016, 5399. (14) For selected examples involving β-oxygen elimination mechanism, see: (a) Wang, Z.; Zhu, L.; Zhong, K.; Qu, L.-B.; Bai, R.; Lan, Y. ChemCatChem 2018, 10, 5280. (b) Dou, X.; Liu, N.; Yao, J.; Lu, T. Org. Lett. 2018, 20, 272. (c) Jiang, X.; Chen, J.; Zhu, W.; Cheng, K.; Liu, Y.; Su, W.-K.; Yu, C. J. Org. Chem. 2017, 82, 10665. (d) Kalsi, D.; Laskar, R. A.; Barsu, N.; Premkumar, J. R.; Sundararaju, B. Org. Lett. 2016, 18, 4198. (e) Kong, L.; Yu, S.; Tang, G.; Wang, H.; Zhou, X.; Li, X. Org. Lett. 2016, 18, 3802. (f) Mei, S.-T.; Wang, N.-J.; Ouyang, Q.; Wei, Y. Chem. Commun. 2015, 51, 2980.

E

DOI: 10.1021/acs.orglett.9b01333 Org. Lett. XXXX, XXX, XXX−XXX