Cu-Catalyzed Enantioselective Ring Opening of Cyclic

Jul 17, 2018 - A Cu-catalyzed enantioselective desymmetrizing ring-opening reaction ... or thioacids is reported for the facile access to chiral diary...
0 downloads 0 Views 1MB Size
Download PDF
Communication Cite This: J. Am. Chem. Soc. 2018, 140, 9400−9403

pubs.acs.org/JACS

Cu-Catalyzed Enantioselective Ring Opening of Cyclic Diaryliodoniums toward the Synthesis of Chiral Diarylmethanes Bin Li, Zengyin Chao, Chunyu Li, and Zhenhua Gu* Department of Chemistry, Center for Excellence in Molecular Synthesis, and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, P.R. China

Downloaded via UNIV OF WOLLONGONG on August 1, 2018 at 07:44:25 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

Scheme 1. Asymmetric Ring Opening of Cyclic Diaryliodonium

ABSTRACT: A Cu-catalyzed enantioselective desymmetrizing ring-opening reaction of six-membered cyclic diaryliodonium salts with carboxylic acids or thioacids is reported for the facile access to chiral diarylmethanes. A Cu/[cyclopropyl bis(oxazoline)] catalyst well discriminates two C−I bonds of prochiral cyclic diaryliodonium salts. A stereochemical model was proposed to rationalize the stereochemical outcome on the basis of the crystal structure of cyclic diaryliodonium salt.

D

iaryliodonium salts, also known as diaryl-λ3-iodanes, represent an important class of compounds that are widely used in organic synthesis and molecule assembly chemistry.1,2 The highly electron-deficient nature of diaryliodonium salts, in combination with the excellent leaving propensity of Ar−I, renders these compounds powerful arylation reagents in synthetic organic chemistry. Generally, diaryliodonium salts demonstrate higher reactivity profiles than the corresponding aryl iodides in transition-metal-catalyzed arylation reactions. Many elegant transformations of diaryliodonium salts have been developed, including some elegant enantioselective arylations reported by Gaunt and others.3 However, these reactions typically involve acyclic diaryliodonium salts as arylation reagents, which would produce 1 equiv of aryl iodide as the byproduct, reducing their atom economy. Examples where the aryl iodide “byproduct” could be used in situ as the second arylation reagents are very limited.4a However, this drawback has been avoided with the use of cyclic diaryliodoniums, which have been successfully applied in the synthesis of a series of functionalized biaryls.4b−e Cyclic diaryliodonium salts are tricyclic derivatives with an iodonium center, whereby two aryl rings bonding to the iodine atom are bridged. The cyclic diaryliodonium salts exhibit compromised reactivity compared to their acyclic counterparts;1c however, the released aryl iodide moieties still remain within the products and can be used for further elaboration. Until Hayashi and co-workers described a palladium-catalyzed carboxylation reaction of dinaphtho[2,1-b:1′,2′-d]iodol-7-ium in 2004, there had been no study of asymmetric arylation with cyclic diaryliodonium salts.5 However, only low yield (38%) and enantioselectivity (28% ee) were obtained after careful optimization in this report (Scheme 1a). Recently, we reported a Cu/bis(oxazolinyl)pyridine-catalyzed enantioselective ringopening reaction of cyclic diaryliodonium salts with amines to © 2018 American Chemical Society

give ortho-tetrasubstituted biaryl atropisomers with very high enantiomeric excesses (Scheme 1b).6,7 Catalytic asymmetric synthesis of chiral diarylmethane, important motifs found in many pharmaceuticals or biologically active compounds,8 has attracted significant attention. Thus, a number of useful protocols have been developed for construction of these molecules, including asymmetric hydrogenation,9 direct benzylic C−H arylation,10 aryl−benzyl cross coupling,11 Barbier-type addition, and conjugate addition.12 Recently, catalytic asymmetric C−H functionalization of prochiral diarylmethane derivatives has emerged as a highly promising strategy. In 2008, Yu and co-workers described a pyridine-directed Pd(II)/(chiral amino acid)-catalyzed alkylation for the synthesis of chiral pyridin-2-yl diarylmethanes.13 Subsequently, this strategy was applied in synthesis of other functionalized chiral diarylmethanes with carboxylic acid and amides as the direction groups.14,15 Despite these remarkable advances, the development of new methods to access highly functionalized chiral diarylmethane is still desirable, yet challenging. We reasoned that asymmetric ring opening of the six-membered prochiral cyclic diaryliodonium salts would give highly functionalized diarylmethane analogues. The products bear one aryl ring attached to the nucleophiles and the other containing a synthetically versatile C(sp2)−I bond (Scheme 1c). Received: June 1, 2018 Published: July 17, 2018 9400

DOI: 10.1021/jacs.8b05743 J. Am. Chem. Soc. 2018, 140, 9400−9403

Communication

Journal of the American Chemical Society

With the optimal conditions in hand, we examined the scope of this enantioselective ring-opening reaction (Scheme 2).

We started our studies with six-membered cyclic diaryliodonium salt 1a and potassium thioacetate 2a. Initially, Cu(CH3CN)4PF6 was chosen as the catalyst, and various oxazoline-type ligands were screened. The phenyl-substituted bisoxazoline L1 gave the expected product 3a in 28% ee, along with the formation of a small amount of O-arylation of 4a (3a:4a = 17:1) (Table 1, entry 1). Replacing the phenyl group with tert-

Scheme 2. Substrate Scope with Thioatesa

Table 1. Optimization of Reaction Conditionsa

entry

Cu/L

yield

ee/%

3a:4a

1 2 3 4 5 6 7 8 9 10 11 12 13b 14b,c 15

Cu(MeCN)4PF6/L1 Cu(MeCN)4PF6/L2 Cu(MeCN)4PF6/L3 Cu(MeCN)4PF6/L4 Cu(MeCN)4PF6/L5 Cu(MeCN)4PF6/L6 Cu(MeCN)4PF6/L7 Cu(MeCN)4PF6/L8 Cu(OTf)2/L8 CuTC/L8 Cu(OAc)2/L8 CuI/L8 Cu(OTf)2/L8 Cu(OTf)2/L8 Cu(OTf)2/L9

61 70 55 87 47 45 88 81 83 85 79 85 89 93 91

28 7 0 0 3 51 86 93 94 94 93 93 93 93 92

17:1 >20:1 >20:1 >20:1 15:1 10:1 11:1 14:1 14:1 10:1 7:1 13:1 11:1 11:1 13:1

a

Unless stated otherwise, the reaction was conducted with 1a (0.10 mmol), 2a (0.10 mmol), Cu salt (5 mol %), and ligand (5 mol %) in dichloroethane (DCE) (2.0 mL) at 60 °C for 10 h. b1.2 equiv of 2a was used. c1a (0.20 mmol), 2a (0.20 mmol), and 2.0 mL of DCE were used.

Unless stated otherwise, the reaction was conducted with 1 (0.20 mmol), 2 (0.24 mmol), Cu(OTf)2 (5.0 mol %), and L8 (5.0 mol %) in dichloroethane (2.0 mL) at 60 °C for 10 h. rr = regioisomeric ratio.

butyl or benzyl groups did not improve the stereoinduction, albeit the O-arylation reaction was suppressed (entries 2 and 3). Surprisingly, bis(oxazolinyl)pyridine ligand L4 affected no stereoinduction (entry 4). Further optimization focused on the effects of some spirobis(oxazoline) ligands L5−L7 (entries 5−7). The enantioselectivities jumped from 3% to 51% when the ring size was reduced from cyclohexane to cyclopentane structure, though the regioisomeric ratio decreased to 10:1. The enantioselectivity was improved to 86% with cyclopropane derivative L7 as the ligand, whose analogues L8 and L9 afforded product 3a in 92−93% ee (entries 8 and 15). The dramatic increment of enantioselectivity from dimethyl- to cyclopropylbased bis(oxazoline) may be attributed to the increased bite angle of two oxazoline moieties.16 The sources of copper salts were screened and found to have a marginal effect on the enantioselectivity (entries 9−12). Further tuning the molar ratio of 1a:2a and the concentration of the reaction improved the yield of this asymmetric ring-opening reaction (entries 13 and 14). Thus, we established the optimal catalyst system: Cu(OTf)2/L8 with 1.2 equiv of 2a in dichloroethane with the concentration of 1a being 0.10 mol/L.

Substituted potassium thioacetates, such as 3-phenylpropanoic thioacid, 2-(phenylthio)acetic thioacid, and cyclohexanecarboxylic thioacid, improved the enantioselectivity to 95−97% (3b− 3d). Steric properties of the carboxylic ester did not affect the stereoinduction (3e and 3f). Introducing methyl or methoxyl groups to the para position of the C−I bond has a marginal effect on the enantioselectivity (3g and 3h). To our delight, the C−F, C−Cl, and C−Br bonds are also compatible, with a very slight decrease in enantioselectivity (3i−3l). The meta-substituent to the C−I bond had a slightly negative impact on the enantioselectivity; for these substrates the reactions were performed at a lower temperature (50 °C) with prolonged reaction time (3m and 3n). Generally, the enantioselection is better for the Weinreb amide or N-methylphenyl amide as compared to carboxylic esters, and up to 97% ee was achieved (3o−3t). The structure and absolute (S)-configuration of the ring-opening products were unambiguously established by single-crystal X-ray diffraction analysis of compound 3o.17 This asymmetric ring-opening reaction was also applied to the oxygen nucleophiles, such as potassium carboxylates (Scheme 3). Generally, the rate with carboxylates as nucleophiles was

a

9401

DOI: 10.1021/jacs.8b05743 J. Am. Chem. Soc. 2018, 140, 9400−9403

Communication

Journal of the American Chemical Society Scheme 3. Substrate Scope with Carboxylatesa

Scheme 4. Plausible Catalytic Cycle and Stereoinduction Models

a The reaction was conducted with 1 (0.20 mmol), 5a (0.24 mmol), Cu(OTf)2 (5.0 mol %), and L8 (5.0 mol %) in DCE (2.0 mL) at 60 °C for 48 h.

much slower than those with S-nucleophiles in this Cu-catalyzed ring-opening reaction, which is consistent with the observed ratio of S/O-arylation with thioacetates as nucleophiles. Regardless of the substituents on the phenyl rings, excellent enantioselectivity was achieved (6a−6d). The functional groups in the aliphatic chain, such as Weinreb amide, ester, or amide, had slight effects on the ee values (6e and 6f). To gain some insight regarding the stereoinduction of this Cucatalyzed asymmetric ring-opening reaction, a single crystal of cyclic diaryliodonium salt 1n was obtained by slow evaporation of the solvent [petroleum ether/ethyl acetate] and its structure solved (Figure 1).18 The compound has a “Λ”-shape structure in

addition with cyclic iodonoium salt 1n to deliver B. The coordination of potassium thioates 2 to the Cu(III) center gave C, which would give the final products 3 via reductive elimination. To rationalize the result of stereoinduction, the Cu catalyst would interact with 1n from the convex side, while the approach to the concave side is sterically disfavored [Scheme 4, I (top view) and II (side view)]. In this scenario, stronger steric repulsion between the 3,5-dimethylphenyl group of bisoxazoline L8 and the alkyl chain {CH2CO2Et]} would be generated in stereochemical model IV than that in III. Thus, breaking of the left C(sp2)−I bond in I is favored to deliver the product with S-configuration. Finally a brief synthetic application of the obtained thioesters was demonstrated (Scheme 5). Hydrolysis of thioester and Scheme 5. Synthetic Application

carboxylic ester of 3g, followed by cyclization, would give thioester 7 in 68% overall yield. The Sonogashira coupling of 7 gave alkyne 8 uneventfully with 91% ee. In conclusion, we have disclosed an asymmetric ring-opening reaction of diaryliodoniums to access molecules with center chirality. Optically active functionalized diarylmethane derivatives that bear (thio)phenol and versatile C(sp2)−I functionalities have been synthesized in high yields and enantioselectivity. On the basis of X-ray diffraction analysis, it was found that the cyclic diaryliodonium salt showed “Λ”-shape structure in the solid state. A model for the stereochemical outcome has been proposed.

Figure 1. Crystal structure of 1n. (a) Dihedral angle of the two phenyl rings (CF3SO3− was omitted). (b) Top view. (c) Side view.

the solid state, with the dihedral angle of the two phenyl rings being 124° (Figure 1a). The six-membered iodonium heterocycle adopts a boat-like conformation (Figure 1b and 1c), where the alkyl chain locates at the equatorial position and the hydrogen atom is at the axial position. A plausible catalytic cycle as well as the chemical structure of 1n and the possible stereochemical models were shown in Scheme 4. On the basis of previous computational studies,19 the Cu(I)/bis(oxazoline) A was regarded as the active catalyst, which underwent oxidative

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.8b05743. Experimental procedures and spectroscopic data (PDF) 9402

DOI: 10.1021/jacs.8b05743 J. Am. Chem. Soc. 2018, 140, 9400−9403

Communication

Journal of the American Chemical Society

■

(8) (a) Hills, C. J.; Winter, S. A.; Balfour, J. A. Drugs 1998, 55, 813− 820. (b) McRae, A. L.; Brady, K. T. Expert Opin. Pharmacother. 2001, 2, 883. (c) Gordaliza, M.; García, P. A.; Miguel del Corral, J. M.; Castro, M. A.; Gómez-Zurita, M. A. Toxicon 2004, 44, 441. (d) Li, S.-G.; Huang, X.-J.; Li, M.-M.; Liu, Q.; Liu, H.; Wang, Y.; Ye, W.-C. J. Nat. Prod. 2018, 81, 254−263. (9) (a) Woodmansee, D. H.; Pfaltz, A. Chem. Commun. 2011, 47, 7912. (b) Wang, X.; Guram, A.; Caille, S.; Hu, J.; Preston, J. P.; Ronk, M.; Walker, S. Org. Lett. 2011, 13, 1881. (10) Yan, S.-B.; Zhang, S.; Duan, W.-L. Org. Lett. 2015, 17, 2458− 2461. (11) (a) Do, H.-Q.; Chandrashekar, E. R. R.; Fu, G. C. J. Am. Chem. Soc. 2013, 135, 16288−16291. (b) Ackerman, L. K. G.; Anka-Lufford, L. L.; Naodovic, M.; Weix, D. J. Chem. Sci. 2015, 6, 1115−1119. (c) Gutierrez, O.; Tellis, J. C.; Primer, D. N.; Molander, G. A.; Kozlowski, M. C. J. Am. Chem. Soc. 2015, 137, 4896−4899. (d) Friis, S. D.; Pirnot, M. T.; Buchwald, S. L. J. Am. Chem. Soc. 2016, 138, 8372− 9375. (e) Logan, K. M.; Brown, M. K. Angew. Chem., Int. Ed. 2017, 56, 851−855. (f) Poremba, K. E.; Kadunce, N. T.; Suzuki, N.; Cherney, A. H.; Reisman, S. E. J. Am. Chem. Soc. 2017, 139, 5684−5687. (12) (a) Hayashi, T.; Ishigedani, M. J. Am. Chem. Soc. 2000, 122, 976− 977. (b) Hermanns, N.; Dahmen, S.; Bolm, C.; Bräse, S. Angew. Chem., Int. Ed. 2002, 41, 3692−3694. (c) Hayashi, T.; Kawai, M.; Tokunaga, N. Angew. Chem. 2004, 116, 6251−6254. (d) Tokunaga, N.; Otomaru, Y.; Okamoto, K.; Ueyama, K.; Shintani, R.; Hayashi, T. J. Am. Chem. Soc. 2004, 126, 13584−13585. (e) Kuriyama, M.; Soeta, T.; Hao, X.; Chen, Q.; Tomika, K. J. Am. Chem. Soc. 2004, 126, 8128−8129. (f) Jagt, R. B. C.; Toullec, P. Y.; Geerdink, D.; de Vries, J. G.; Feringa, B. L.; Minnaard, A. J. Angew. Chem., Int. Ed. 2006, 45, 2789−2791. (g) Duan, H.-F.; Jia, Y.-X.; Wang, L.-X.; Zhou, Q.-L. Org. Lett. 2006, 8, 2567− 2569. (h) Wang, Z.-Q.; Feng, C.-G.; Xu, M.-H.; Lin, G.-Q. J. Am. Chem. Soc. 2007, 129, 5336−5337. (13) Shi, B.-F.; Maugel, N.; Zhang, Y.-H.; Yu, J.-Q. Angew. Chem., Int. Ed. 2008, 47, 4882−4886. (14) (a) Shi, B.-F.; Zhang, Y.-H.; Lam, J. K.; Wang, D.-H.; Yu, J.-Q. J. Am. Chem. Soc. 2010, 132, 460−461. (b) Cheng, X.-F.; Li, Y.; Su, Y.-M.; Yin, F.; Wang, J.-Y.; Sheng, J.; Vora, H. U.; Wang, X.-S.; Yu, J.-Q. J. Am. Chem. Soc. 2013, 135, 1236−1239. (c) Chu, L.; Wang, X.-C.; Moore, C. E.; Rheingold, A. L.; Yu, J.-Q. J. Am. Chem. Soc. 2013, 135, 16344− 16347. (d) Laforteza, B. N.; Chan, K. S. L.; Yu, J.-Q. Angew. Chem., Int. Ed. 2015, 54, 11143−11146. (15) For some other desymmetrization examples, see (a) Du, Z.-J.; Guan, J.; Wu, G.-J.; Xu, P.; Gao, L.-X.; Han, F.-S. J. Am. Chem. Soc. 2015, 137, 632−635. (b) Kim, B.; Chinn, A. J.; Fandrick, D. R.; Senanayake, C. H.; Singer, R. A.; Miller, S. J. J. Am. Chem. Soc. 2016, 138, 7939−7945. (c) Hurtley, A. E.; Stone, E. A.; Metrano, A. J.; Miller, S. J. J. Org. Chem. 2017, 82, 11326−11336. (16) Davies, I. W.; Gerena, L.; Castonguay, L.; Senanayake, C. H.; Larsen, R. D.; Verhoeven, T. R.; Reider, P. J. Chem. Commun. 1996, 1753−1754. (17) CCDC 1845461 contains the supplementary crystallographic data for compound 3o. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre. (18) CCDC 1845462 contains the supplementary crystallographic data for compound 1n. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre. (19) (a) Ichiishi, N.; Canty, A. J.; Yates, B. F.; Sanford, M. S. Org. Lett. 2013, 15, 5134−5137. (b) Ichiishi, N.; Canty, A. J.; Yates, B. F.; Sanford, M. S. Organometallics 2014, 33, 5525−5534. (c) Chen, B.; Hou, X.-L.; Li, Y.-X.; Wu, Y.-D. J. Am. Chem. Soc. 2011, 133, 7668− 7671.

Data for C19H20INO3S (CIF) Data for C22H24IO5F3S (CIF)

AUTHOR INFORMATION

Corresponding Author

*[email protected] ORCID

Zhenhua Gu: 0000-0001-8168-2012 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We are grateful for financial support from NSFC (21622206, 21472179), the ‘973’ project from the MOST of China (2015CB856600), Strategic Priority Research Program of the Chinese Academy of Sciences (XDB20000000), and Fundamental Research Funds for the Central Universities (WK2060190086).

■

REFERENCES

(1) (a) Banks, D. F. Chem. Rev. 1966, 66, 243−266. (b) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 1996, 96, 1123−1178. (c) Grushin, V. V. Chem. Soc. Rev. 2000, 29, 315−324. (d) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2008, 108, 5299−5358. (e) Merritt, E. A.; Olofsson, B. Angew. Chem., Int. Ed. 2009, 48, 9052−9070. (f) Yoshimura, A.; Zhdankin, V. V. Chem. Rev. 2016, 116, 3328−3435. (2) (a) Beringer, F. M.; Galton, S. A.; Huang, S. J. J. Am. Chem. Soc. 1962, 84, 2819−2823. (b) Kang, S.-K.; Lee, S.-H.; Lee, D. Synlett 2000, 1022−1024. (c) Phipps, R. J.; Grimster, N. P.; Gaunt, M. J. J. Am. Chem. Soc. 2008, 130, 8172−8174. (d) Phipps, R. J.; Gaunt, M. J. Science 2009, 323, 1593−1597. (e) Zhu, D.; Liu, Q.; Luo, B.; Chen, M.; Pi, R.; Huang, P.; Wen, S. Adv. Synth. Catal. 2013, 355, 2172−2178. (f) Sokolovs, I.; Lubriks, D.; Suna, E. J. Am. Chem. Soc. 2014, 136, 6920−6928. (g) Liu, Z.; Zhu, D.; Luo, B.; Zhang, N.; Liu, Q.; Hu, Y.; Pi, R.; Huang, P.; Wen, S. Org. Lett. 2014, 16, 5600−5603. (h) Berzina, B.; Sokolovs, I.; Suna, E. ACS Catal. 2015, 5, 7008−7014. (i) Wu, B.; Yoshikai, N. Angew. Chem., Int. Ed. 2015, 54, 8736−8739. (j) Xie, H.; Ding, M.; Liu, M.; Hu, T.; Zhang, F. Org. Lett. 2017, 19, 2600−2603. (k) Caramenti, P.; Nicolai, S.; Waser, J. Chem. - Eur. J. 2017, 23, 14702−14706. (l) Yang, S.; Wang, F.; Wu, Y.; Hua, W.; Zhang, F. Org. Lett. 2018, 20, 1491−1495. (m) Grenet, E.; Waser, J. Org. Lett. 2018, 20, 1473−1476. (n) Wang, M.; Fan, Q.; Jiang, X. Org. Lett. 2018, 20, 216−219. (3) (a) Bigot, A.; Williamson, A. E.; Gaunt, M. J. J. Am. Chem. Soc. 2011, 133, 13778−13781. (b) Zhu, S.; MacMillan, D. W. C. J. Am. Chem. Soc. 2012, 134, 10815−10818. (c) Cahard, E.; Male, H. P.; Tissot, M.; Gaunt, M. J. J. Am. Chem. Soc. 2015, 137, 7986−7989. (d) Beaud, R.; Phipps, R.; Gaunt, M. J. J. Am. Chem. Soc. 2016, 138, 13183−13186. (e) Lukamto, D. H.; Gaunt, M. J. J. Am. Chem. Soc. 2017, 139, 9160−9163. (f) Rae, J.; Frey, J.; Jerhaoui, S.; Choppin, S.; Wencel-Delord, J.; Colobert, F. ACS Catal. 2018, 8, 2805−2809. (4) (a) Modha, S. G.; Greaney, M. F. J. Am. Chem. Soc. 2015, 137, 1416−1419. (b) Luo, S.-J.; Ma, Y.-X.; Liang, Y. Molecules 2005, 10, 238−243. (c) Luo, B.; Cui, Q.; Luo, H.; Hu, Y.; Huang, P.; Wen, S. Adv. Synth. Catal. 2016, 358, 2733−2738. (d) Wang, M.; Wei, J.; Fan, Q.; Jiang, X. Chem. Commun. 2017, 53, 2918−2921. (e) Wang, M.; Fan, Q.; Jiang, X. Org. Lett. 2018, 20, 216−219. (5) Kina, A.; Miki, H.; Cho, Y.-H.; Hayashi, T. Adv. Synth. Catal. 2004, 346, 1728. (6) Zhao, K.; Duan, L.; Xu, S.; Jiang, J.; Fu, Y.; Gu, Z. Chem 2018, 4, 599−612. (7) See other asymmetric ring-opening reactions: (a) Bringmann, G.; Menche, D. Acc. Chem. Res. 2001, 34, 615−624. (b) Shimada, T.; Cho, Y.-H.; Hayashi, T. J. Am. Chem. Soc. 2002, 124, 13396. (c) Bringmann, G.; Mortimer, A. J. P.; Keller, P. A.; Gresser, M. J.; Garner, J.; Breuning, M. Angew. Chem., Int. Ed. 2005, 44, 5384−5427. 9403

DOI: 10.1021/jacs.8b05743 J. Am. Chem. Soc. 2018, 140, 9400−9403